Chemical Constituents and Biological Activity Profiles on Pleione (Orchidaceae).

Pleione (Orchidaceae) is not only famous for the ornamental value in Europe because of its special color, but also endemic in Southern Asia for its use in traditional medicine. A great deal of research about its secondary metabolites and biological activities has been done on only three of 30 species of Pleione. Up to now, 183 chemical compounds, such as phenanthrenes, bibenzyls, glucosyloxybenzyl succinate derivatives, flavonoids, lignans, terpenoids, etc., have been obtained from Pleione. These compounds have been demonstrated to play a significant role in anti-tumor, anti-neurodegenerative and anti-inflammatory biological activities and improve immunity. In order to further develop the drugs and utilize the plants, the chemical structural analysis and biological activities of Pleione are summarized in this review.

1. Introduction

Orchidaceae is one of the largest family of flowering plants. There are about 42 genus that are used for traditional medicine in China, but thus far, no phytochemical investigation has been conducted on 70% of them [1]. As one of unexplored medicinal orchid [2], Pleione contains about 30 species in the habitats of terrestrial, epiphytic or lithophytic, among which 12 are endangered [3]. It mainly distributes in China, Vietnam, Burma, Bangladesh and the Northeast Indian at elevation of 600–4200 m [4]. China is the central region, with 23 species distributed here and 12 of them are endemic [5,6,7,8].

The Pleione is attracting increasing attention nowadays in terms of the ornamental and medicinal values [9,10,11]. As a special colorful flower, Pleione was introduced to Europe from China in 1904 [4]. Currently, there are more than 400 cultivars [12]. In China, the dry pseudobulbs of P. bulbocodioides and P. yunnanensis, as well as Cremastra appendiculata, were the sources of the traditional Chinese medicine (TCM) ‘shan-ci-gu’. They are used for removing heat, counteracting toxicity, dissipating phlegm and resolving masses. They can also be applied on symptoms such as furuncles, carbuncles, scrofulous sputum, snake and insect bites, abdominal masses and lumps [13]. However, only three species of Pleione, including P. humulis, P. praecox and P. maculate, were used as traditional medicine in Northeastern India, applied on laceration wounds, colds, upper respiratory infection, liver complaints and stomach ailments [2]. In summary, five species have been commonly used in traditional medicines, but scientific studies have only been performed on three of them. More detailed research is needed to on Pleione.

The phytochemical research could be traced back to 1996. Li et al. [14,15,16,17,18,19,20] extracted 30 chemical compounds from the pseudobulbs of P. bulbocodioides, such as dihydrophenanthropyrans, bibenzyls, bichroman, polyphenol and flavan-3-ol. Among them, the dihydrophenanthropyran 35 was the first one isolated from Pleione and the chemical structure of dihydrophenanthropyran with a 4H [2, 1-b] pyran system was reported [15]. Although China is the Pleione distribution center, there was no phytochemical investigation there until 2007. Liu [1] initiated the chemical investigation of P. bulbocodioides leading to six novel compounds and 24 known compounds, among which 18 compounds were obtained from the Pleione for the first time. In addition, the ethyl acetate (EtOAc) extracted fraction from P. bulbocodioides was found to have a certain inhibitory effect on mice cancer cells LA795, exerting significant activity of anti-tumor. Since then, the EtOAc fraction has been the key research part. Due to few researches focused on P. yunnanensis, Dong et al. [21,22,23] carried out the phytochemical on P. yunnanensis in 2009, discovering 12 novel compounds and 12 known compounds. In addition, since the pseudobulbs of P. formosana have been used as the substitute of Shan-ci-gu in Taiwan Island, Shiao [24] performed chemical investigation on them in 2009 and isolated three novel compounds.

The structural diversity of Pleione prompted Wang’s group [25,26] to continue the phytochemical investigation and isolated sixty compounds from P. bulbocodiodes and P. yunnanensis, occupied more than 30% of the total compounds. It is noteworthy that all compounds were tested for several assays of biological activities in vitro, generally known as free radical scavenging activity, cytotoxic activity, inhibition of NO production activity and neurotoxicity activity. In addition, the experiment turned to the study on the high-polarity fraction, which led to the isolation of 10 glucosyloxybenzyl succinate derivatives [27]. Encouraged by previous phytochemical researches on Pleione, Li et al. [28,29] isolated pyrrolidone substituted bibenzyls and prenylated flavones from P. bulbocodiodes, which enriched the contents of the chemical constituents.

Moreover, there were 152 patents published referring to the Pleione in China; 88.8% of them were related to the pharmacological activity against breast cancer, lung cancer, liver cancer, stomach cancer, colon cancer, etc. In order to benefit future research on the phytochemistry and biological of the Pleione, this review will discuss about the chemical compound isolation from the Pleione, structural analysis of the metabolites and the corresponding biological activities evaluation.

2. Chemical Constituents

2.1. Phenanthrenes

Phenanthrenes is one of the typical compounds extracted from the Pleione [30]. Fifty-seven phenanthrenes have been isolated (Table 1 & Figure 1), including three simple dihydrophenanthrenes (1–3), 10 benzyl substituted dihydrophenanthrenes (4–10, 21–23), three dihydrophenanthrene dimers (11–13), five dimers of phenanthrene (15–17, 24, 25), three phenanthrene and dihydrophenanthrene polymers (14, 18–19), three dihydrophenanthrene and bibenzyl polymers (20, 26, 27), one dihydrophenanthrene and glycoside polymer (28), 18 dihydrophenanthrene and phenylpropanoid polymers (29–46), one phenanthrene and phenylpropanoid polymers (47) and 10 phenanthrene polymers (48–57). The spectroscopic data of Compound 1–57 are shown in Table 2 and Table 3. Of these compounds, the dihydrophenanthrene 1, 3 and the bibenzyls 58 and 61 may be the main bioactive compounds for anti-tumor, anti-inflammatory and anti-oxidant activities, which might also be the result of their synergy [31]. The 27 was the first dihydrophenanthrene component connected with the bibenzyl isolated from the Pleione [15]. Three novel 9, 10-dihydrophenanthrofurans 29–31 were isolated by Dong in 2009 [21]. The properties of 9, 10-dihydrophenanthrofurans with a phenyl from the Pleione species were may be deemed to be a chemtaxonomic marker of this species. One dihydrophenanthrene connecting with a β-d-glucopyranosyl 28 as the first reported structure of glucosyloxybenzyl 2-isobutylmalates in Pleione was also obtained in 2013 [22]. The compounds synthesized by aldol reaction of condensation of acetone with 9, 10-phenanthrene were firstly obtained from Pleione 48, 49 by Wang [25] in 2014. Wang [26] demonstrated that there was a structure-biological activity relationship of phenanthrenes isolated from P. yunnanensis. The structure of 39 is very similar with 40, but the former showed stronger neurotoxic activity than the latter. This is because that the carbon-9′ (C9′) of 39 is acetylation, resulting in the carbonyl oxygen atom hydrogen to the receptor. Based on Wang’s research [25], Shao [32] determined eight phenanthrenequinone enantiomers configuration of 50–57 by means of the spectroscopy techniques, such as Nuclear Magnetic Resonance (NMR), High Resolution Electrospray Ionization Mass Spectroscopy (HRESIMS) and Executive Creative Director (ECD). The possible biosynthetic pathways can be inferred based on structural analysis.

Table 1

Phenanthrenes from Pleione genus.

No.	Compound	Plant	Reference	No.	Compound	Plant	Reference
1	Coelonin	B *, Y *	[22,29]	30	Pleionesin B	Y	[33,34]
2	Lusianthridin	B, Y	[22,29]	31	Pleionesin C	Y	[33,34]
3	Hircinol	B	[33]	32	Shanciol H	B, Y	[21,35]
4	4, 7-dihydroxy-1-(p-hydroxybenzyl)-2-methoxy-9, 10-dihydrophenanthrene	Y	[22,34]	33	(4′-hydroxy-3′-methoxyphenyl)-10-hydroxymethyl-11-methoxy-5, 6, 9, 10-tetrahydrophenanthrene[2, 3-b]furan-3-ol	B	[36]
5	2, 7-dihydroxy-4-methoxy-1-(p-hydroxybenzyl)-9, 10-dihydrophenanthrene	Y	[22]	34	hydroxy-9-(4′-hydroxy-3′-methoxyphenyl)-11-methoxy-5, 6, 9, 10-tetrahydroohenanthrene-azaspiro[2, 3-b]furan-10-yl)methylethyl	B	[37]
6	1-(p-hydroxybenzyl)-4, 7-dihydroxy-2-methoxy-9, 10-dihydrophenanthrene	B	[6]	35	Shanciol	B, Y	[15]
7	Pleioanthrenin	F *	[24]	36	Shanciol E	B	[20]
8	2, 7-dihydroxy-1-(p-Hydroxybenzyl)-4-methoxy-9, 10-diphenanthrene	B, Y	[22,33]	37	(7′S, 8′R)-7-hydroxy-7-(4′-hydroxy-3′, 5′-dimethoxy-phenyl)-8′-hydroxymethyl-5-methoy-9, 10, 7′, 8-tetra hydro-phenanthrene-[2, 3-b]furan	B	[25]
9	(4-Hydroxybenzyl)-4-methoxy-9, 10-dihydrophenanthrene-2, 7-diol	B	[28]	38–39	Pleionesin D–E	Y	[25]
10	(4-hydroxybenzyl)-4, 7-dimethoxy-9, 10-dihydrophenanthrene-2-ol	B, F	[24,28]	40	(7′, 8′-trans)-7-hydroxy-10-methoxy-7′-(4′-hydroxy-3′-methoxyphenyl)-8′-hydoxymethyl-9, 10, 7′, 8′-tetrahydro-[2, 1-b]furan	Y	[26]
11	Blestrianol A	B	[25]	41–43	Bletilol A–C	B	[11,15]
12	4, 4′, 7, 7′-tetrahydroxy-2,2′-dimethoxy-9, 9′, 10, 10′-tetrahydro-1, 1′-biphenanthrene	B	[28]	44	Shanciol F	B, Y	[20,21]
13	Blestriarene A	B	[33,34]	45	Shanciols C	B	[19]
14	Blestriarene B	B	[21]	46	Shanciol G	B	[35]
15	Blestriarene C	Y	[22]	47	Shanciols D	B	[19]
16–20	Bulbocodioidin G–K	B	[25]	48	Bulbocodioidin A	B	[25]
21	1-(p-hydroxybenzyl)-2, 7-dihydroxy-4-methoxy-phenanthrene	B	[22]	49	Bulbocodioidin B	B	[25]
22	Shancidin	Y	[22]	50	(9R) bulbocodioidins A	B	[32]
23	7-hydroxy-2,4-dimethoxy-1-(p-hydroxybenzyl)-pHenanthrene	Y	[33]	51	(9S) Bulbocodioidins A	B	[32]
24	Monbarbatain A	B	[33]	52	(9R) Bulbocodioidins B	B	[32]
25	2, 7, 2′-didroxy-4, 4′, 7′-trimethoxy-1, 1′-biphenanthrene	B	[28]	53	(9S) Bulbocodioidins B	B	[32]
26	Phoyunnanin A	B	[28]	54	(9R) Bulbocodioidins C	B	[32]
27	Shancilin	B	[14]	55	(9S) Bulbocodioidins C	B	[32]
28	Shancigusins G	B, Y	[22]	56	(10S) Bulbocodioidins D	B	[32]
29	Pleionesin A	Y	[21]	57	(10R) Bulbocodioidins D	B	[32]

Note: * B: bulbocodioides; * Y: yunnanensis; * F: formosana. The same as below.

Figure 1

The structures of Phenanthrenes.

Table 2

13C NMR data of compounds 1–57.

No.	Solvent	Position
		1	2	3	4	4a	4b	5	6	7	8	8a	9	10	10a
1	MeOH-d4	106.9	154.6	97.9	157.7	115.4	124.8	128.6	112.2	156.0	113.6	139.1	30.4	29.8	140.4
2	MeOH-d4	108.3	159.1	99.3	156.1	116.8	126.2	130.0	115.0	157.5	113.6	140.5	31.8	31.2	141.8
3	Acetone-d6	109.7	156.3	99.8	158.5	114.6	128.1	154.7	118.2	120.1	128.1	144.1	31.6	31.8	141.3
4	Acetone-d6	118.0	156.8	98.9	155.1	117.1	125.9	130.1	114.5	156.1	113.4	139.8	30.5	27.1	140.4
5	DMSO-d6	116.9	154.2	98.0	155.1	115.0	124.1	128.8	112.6	155.0	113.8	138.5	19.4	26.0	138.9
6	MeOH-d4	-	-	-	-	-	-	-	-	-	-	-	-	-	-
7	MeOH-d4	118.3	156.0	96.1	156.3	120.1	126.1	130.5	130.5	157.4	114.6	140.6	30.9	27.5	140.7
8	DMSO-d6	116.9	154.2	98.0	155.1	115.0	124.1	128.8	112.6	155.0	113.8	138.5	19.4	26.0	138.9
9	MeOH-d4	118.6	157.2	99.3	155.6	117.5	126.5	130.3	114.6	156.0	113.5	140.4	30.9	27.4	140.9
10	MeOH-d4	141.6	155.4	99.1	158.5	117.5	126.5	130.3	113.5	156.1	114.7	140.8	31.0	28.2	140.3
11	Acetone-d6	120.3	157.8	115.2	155.4	116.8	125.6	129.1	112.0	156.0	114.1	140.8	30.7	28.3	140.1
12	Acetone-d6	118.4	157.6	99.4	155.1	115.8	126.3	130.2	113.4	156.1	114.7	140.2	30.6	28.4	141.1
13	MeOH-d4	115.7	158.4	98.9	155.4	117.5	126.5	130.3	113.5	156.1	114.7	141.6	31.0	28.2	140.8
14	MeOH-d4	115.0	160.3	100.3	155.4	117.8	126.6	130.5	113.6	155.4	114.8	142.4	30.9	28.3	140.8
15	MeOH-d4	111.0	157.8	99.6	153.2	114.2	123.5	128.7	110.7	154.0	116.6	133.4	126.7	124.7	132.4
16	Acetone-d6	109.2	155.3	98.3	160.0	112.3	126.4	130.2	117.6	155.3	106.0	128.1	154.3	101.4	135.8
17	Acetone-d6	109.3	155.3	98.2	160.0	112.4	126.5	130.2	117.6	155.3	106.0	127.9	154.3	101.3	135.6
18	Acetone-d6	109.9	154.8	98.2	159.7	112.2	126.4	130.2	117.6	155.3	106.1	127.9	154.4	100.9	135.2
19	Acetone-d6	111.0	154.6	100.3	160.0	116.2	126.1	130.1	117.2	157.6	109.1	133.9	128.6	125.4	134.7
20	MeOH-d4	116.2	154.7	99.0	157.9	116.8	126.3	130.1	113.4	156.0	114.7	140.2	30.7	28.2	140.8
21	Acetone-d6	114.4	153.5	100.2	158.4	116.4	125.4	130.3	117.3	155.2	111.9	133.8	128.2	124.4	133.7
22	MeOH-d4	-	-	-	-	-	-	-	-	-	-	-	-	-	-
23	Acetone-d6	117.0	156.2	97.1	159.1	117.0	125.4	130.7	117.5	155.9	112.3	134.1	128.7	124.6	133.5
24	Acetone-d6	110.0	160.2	100.4	155.1	116.5	125.4	130.2	112.0	155.3	117.4	135.1	128.3	125.6	134.1
25	Chloroform-d	105.7	153.2	98.5	160.4	116.6	125.0	129.4	117.0	156.0	108.4	133.1	129.1	123.9	133.8
26	Acetone-d6	106.1	159.4	101.6	156.0	115.8	126.2	132.9	120.9	154.0	115.6	139.4	30.5	31.6	141.5
27	MeOH-d3	100.9	158.8	98.9	157.1	114.8	140.0	126.9	112.7	153.6	110.6	135.2	30.0	30.5	136.9
28	MeOH-d4	101.2	156.4	108.4	159.9	118.6	125.6	131.0	113.9	156.5	115.0	140.8	31.2	31.9	141.9
29	MeOH-d4	109.2	158.8	125.0	125.2	127.6	116.8	159.1	99.3	157.7	108.3	142.0	31.8	31.5	140.7
30	MeOH-d4	116.0	160.8	94.1	160.0	118.5	126.3	130.5	114.0	156.6	115.3	140.5	31.1	28.2	138.1
31	MeOH-d4	115.7	160.5	93.9	159.7	118.2	126.0	130.2	113.7	156.2	115.0	140.2	30.8	27.9	137.8
32	MeOH-d4	109.5	159.1	125.3	125.5	127.9	117.1	159.4	99.6	158.0	108.6	142.3	32.1	31.8	141.0
33	MeOH-d4	104.9	159.6	117.3	155.2	120.3	124.6	128.0	113.1	155.6	114.0	139.5	29.9	30.8	141.8
34	MeOH-d4	106.2	160.5	117.7	156.4	121.7	125.6	129.2	114.4	156.9	115.2	140.7	31.0	32.0	143.5
35	MeOH-d3	132.0	112.1	99.8	157.6	118.8	126.1	130.4	114.8	156.4	113.7	140.4	26.5	30.7	139.9
36	MeOH-d3	131.1	154.7	99.8	157.7	118.9	126.1	130.4	113.7	156.4	114.8	140.4	26.5	30.7	139.9
37	MeOH-d4	108.7	158.7	125.9	125.2	126.7	116.5	158.7	99.1	157.4	108.1	141.4	31.4.	31.1	139.4
38	Acetone-d6	117.2	158.8	93.5	160.2	116.7	137.0	129.9	113.5	156.0	114.9	139.7	30.4	27.4	136.4
39	MeOH-d4	116.0	160.8	94.2	160.0	118.5	126.3	130.5	114.0	156.6	115.3	140.5	31.1	28.2	138.1
40	MeOH-d4	116.7	160.5	93.9	159.4	118.0	126.2	130.2	113.7	156.2	115.0	140.2	30.9	27.9	137.5
41	MeOH-d4	133.0	153.6	93.0	159.3	114.4	116.9	129.3	113.0	158.5	114.3	136.7	26.9	29.7	134.9
42	MeOH-d4	125.8	153.6	92.9	159.2	114.3	116.8	129.2	114.3	158.4	114.5	136.6	26.8	29.8	133.8
43	MeOH-d4	107.4	146.8	98.3	157.7	116.8	123.8	124.1	125.9	154.7	114.4	133.1	30.4	30.6	133.1
44	MeOH-d3	118.1	159.5	94.0	160.6	116.9	137.6	130.2	113.8	156.2	115.0	140.3	28.0	30.9	135.8
45	MeOH-d3	118.2	159.5	93.9	160.6	116.8	137.7	130.2	113.8	156.3	115.1	140.3	28.0	30.9	136.3
46	MeOH-d4	118.2	160.1	94.3	159.4	118.3	126.1	130.8	113.7	156.3	115.0	140.3	30.9	28.0	137.8
47	MeOH-d3	108.4	159.0	99.5	159.4	125.9	136.5	125.5	134.7	157.7	109.0	142.0	31.6	31.9	117.0
48	MeOH-d4	106.5	158.7	106.6	159.0	118.7	122.3	130.9	115.4	157.7	112.9	141.8	79.8	205.0	133.2
49	MeOH-d4	105.9	159.2	100.5	160.0	112.1	128.9	130.9	121.9	157.1	113.5	132.3	204.7	80.0	143.4
50	MeOH-d4	121.8	157.3	105.1	156.3	118.2	122.8	131.2	115.3	157.3	112.3	141.2	80.0	206.5	132.4
51	MeOH-d4	121.8	157.3	105.1	156.3	118.2	122.8	131.2	115.3	157.3	112.3	141.2	80.0	206.5	132.4
52	MeOH-d4	126.5	155.2	130.0	155.7	123.4	122.6	130.4	116.1	158.1	112.4	141.5	80.0	205.6	130.2
53	MeOH-d4	126.5	155.2	130.0	155.7	123.4	122.6	130.4	116.1	158.1	112.4	141.5	80.0	205.6	130.2
54	MeOH-d4	122.1	157.0	105.7	156.5	119.7	122.9	131.0	114.9	157.0	113.0	141.6	82.5	207.6	131.9
55	MeOH-d4	122.1	157.0	105.7	156.5	119.7	122.9	131.0	114.9	157.0	113.0	141.6	82.5	207.6	131.9
56	MeOH-d4	119.3	157.2	99.8	158.4	113.6	130.9	131.5	121.9	156.9	112.4	132.6	205.7	55.7	139.2
57	MeOH-d4	119.3	157.2	99.8	158.4	113.6	130.9	131.5	121.9	156.9	112.4	132.6	205.7	55.7	139.2

Table 3

1H NMR data of compounds 1–57.

No.	Solvent	Position
		1	3	4	5	6	7	8	9	10
1	MeOH-d4	6.29 d (2.5)	6.38 d (2.5)	-	7.99 d (9.0)	6.61 m	-	6.61 m	2.61 m	2.61 m
2	Acetone-d6	6.36 d (2.0)	6.44 d (2.0)	-	8.03 d (8.5)	-	-	-	2.62 s	2.62 s
3	chloroform-d	6.51 s	-	-	-	6.86 d (7.5)	7.15 dd (8.0, 7.5)	6.95 d (8.0)	2.69–2.70 m	2.65–2.67 m
4	Acetone-d6	-	6.61 s	-	8.01 d (9.0)	6.65 br d (9.0)	-	6.67 br s	2.60 m	2.52 m
5	Acetone-d6	-	6.60 s	-	8.00 d (9.0)	6.65 br d (9.0)	-	6.64 d (2.0)	2.57–2.60 m	2.50–2.53 m
6	chloroform-d	-	6.47, s	-	8.14 d, (8.6)	6.62 m	-	6.60, d, 3.0	2.13–2.61 m	2.13–2.61 m
7	MeOH-d4	-	6.64 s	-	8.00 d (8.0)	6.60 dd (8.0, 2.0)	-	6.62 d (2.0)	2.58 m	2.50 m
8	Acetone-d6	-	6.60 s	-	8.00 d (9.0)	6.65 br d (9.0)	-	6.64 d (2.0)	2.57–2.60 m	2.50–2.53 m
9	MeOH-d4	-	6.51 s	-	7.96 d (8.5)	6.60 dd (8.5, 2.5)	-	6.58 d (2.5)	2.45–2.57 m	2.45–2.57 m
10	MeOH-d4	-	6.57 s	-	8.04 d (8.0)	6.64 dd (8.0, 2.0)	-	6.60 d (2.0)	2.51–2.57 m	2.28–2.36 m
11	MeOH-d4	-	6.57 s	-	8.03 d (8.4)	6.62 dd (8.4, 2.4)	-	6.59 d (2.4)	2.44–2.46 m	2.53–2.55 m
12	Acetone-d6	-	6.58 s	-	8.24 d (8.5)	6.70 dd (8.5, 2.7)	-	6.67 d (2.7)	2.56 m	2.52 m
13	Acetone-d6	-	6.60 s	-	8.09 d (8.5)	6.69 dd (8.5, 3.0)	-	6.66 d (3.0)	2.53 m	2.33 m
14	MeOH-d4	-	-	-	8.09 d (8.8)	6.64 dd (2.8, 8.8)	-	6.56 d (2.8)	2.45 m	2.21 m
15	MeOH-d4	-	6.93 s	-	9.40 d (9.2)	7.03 dd (9.2, 2.8)	-	7.00 d (2.8)	7.23 d (9.2)	6.92 d (9.2)
16	Acetone-d6	-	6.87 s	-	9.50 d (9.6)	7.19 dd (9.6, 2.4)	-	7.61 d (2.4)	-	6.44 s
17	Acetone-d6	-	6.88 s	-	9.51 d (9.0)	7.20 dd (9.0, 3.0)	-	7.62 d (3.0)	-	6.51 s
18	Acetone-d6	-	6.81 s	-	9.47 d (9.6)	7.18 dd (9.6, 3.0)	-	7.65 d (3.0)	-	6.60 s
19	Acetone-d6	-	6.98 s	-	9.52 d (9.6)	7.20 dd (9.6, 3.0)	-	7.31 d (3.0)	-	7.25 d (9.0)
20	Acetone-d6	-	6.59 s	-	8.08 d (9.0)	6.67 dd (9.0, 2.4)	-	6.64 d (2.4)	2.51 m	2.30 m
21	Acetone-d6	-	6.99 s	-	9.43 d (9.5)	7.12 dd (9.5)	-	7.19 d (2.5)	7.53 d (9.5)	7.80 d (9.5)
22	chloroform-d	-	6.47, s	-	8.14 d (8.6)	6.62 m	-	6.60, d, 3.0	2.13–2.61 m	2.13–2.61 m
23	Acetone-d6	-	7.24 s	-	9.55 d (9.0)	7.24 dd (9.0, 2.0)	-	7.30 d (2.0)	7.64 d (9.5)	7.92 d (9.5)
24	Acetone-d6	-	7.02 s	-	9.51 d (8.4)	7.19 dd (8.4, 3.0)	-	7.18 d (3.0)	7.37 d (9.0)	7.03 d (9.0)
25	chloroform-d	-	7.05 s	-	9.57 d (10.0)	7.29 dd (10.0, 3.0)	-	7.18 d (3.0)	7.49 d (8.5)	7.11 d (8.5)
26	Acetone-d6	6.39 d (2.5)	6.41 d (2.5)	-	8.21 s	-	-	6.85 s	2.76 m	2.76 m
27	MeOH-d3	-	6.42 d, 2.3	-	7.92 d (8.6)	6.71, dd, 8.6, 2.6	-	6.74, d, 2.6	2.68–2.70, m	2.68–2.70 m
28	MeOH-d4	6.69 d (2.7)	6.45 d (2.7)	-	8.18 d (8.7)	6.60 dd (8.7, 2.7)	-	6.57 d (2.7)	2.58 m	2.63 m
29	MeOH-d4	6.61 s	-	8.00 s	-	6.35 d (2.0)	-	6.26 d (2.0)	2.57–2.62 m	2.57–2.62 m
30	Acetone-d6	-	6.59 s	-	8.04 d (8.4)	6.68 dd (8.4,3.0)	-	6.69 d (3.0)	2.59–2.77 m	2.59–2.77 m
31	MeOH-d4	-	-	-	-	-	-	-	-	-
32	chloroform-d	6.74 s	-	8.07 s	-	6.42 d (2.0)	-	6.36 d (2.0)	2.70–2.71 m	2.70–2.71 m
33	MeOH-d4	6.54 s	-	-	8.00 d (9.0)	6.65 m	-	6.67 d (2.5)	2.68 m	2.68 m
34	MeOH-d4	6.57 s	-	-	8.03 d (9.6)	6.70 dd (9.6, 2.4)	-	6.68 d (2.4)	2.70 m	2.70 m
35	MeOH-d3	-	6.5, s	-	7.99 d (8.5)	6.62 dd (8.5, 2.5)	-	6.64, d, 2.5	2.62, m	2.62, m
36	MeOH-d3	-	6.51 s	-	8.00 d (8.5)	6.62 dd(8.5, 2.6)	-	6.65 d (2.6)	2.60–2.67 m	2.60–2.67 m
37	Acetone-d6	6.68 s	-	-	8.09 s	6.45 d (2.4)	-	6.38 d (2.4)	2.65 m	2.66 m
38	Acetone-d6	-	6.55 s	-	8.03 d (9.0)	6.67 dd (9.0, 2.5)	-	6.67 d (2.5)	2.55–2.73 m	2.55–2.73 m
39	Acetone-d6	-	6.53 s	-	8.09 d (8.5)	6.72 dd (8.5, 2.5)	-	6.69 d (2.5)	-	-
40	Acetone-d6	-	6.54 s	-	8.03 d (9.5)	6.67 dd (9.5, 2.5)	-	6.68 br s	2.63 m	2.63 m
41	MeOH-d4	-	6.53 s	-	8.09 d (8.6)	6.72 dd (8.6, 3.0)	-	6.69 d (3.0)	2.7 m	2.7 m
42	MeOH-d4	-	6.51 s	-	8.09 d (8.4)	6.71 dd (8.4, 2.6)	-	6.69 d (2.6)	2.67–2.69 m	2.67–2.69 m
43	MeOH-d4	6.34 d (2.1)	6.42 d (2.1)	-	8.08 s	-	-	6.74 s	2.67–2.76 m	2.67–2.76 m
44	MeOH-d3	-	6.54 s	-	7.99 d (9.4)	6.62 m	-	6.61 d (2.6)	2.56–2.70 m	2.56–2.70 m
45	MeOH-d3	-	6.56 s	-	8.00 d (9.2)	6.62 dd (9.6, 2.8)	-	6.61 d (2.8)	2.59–2.71 m	2.59–2.71 m
46	MeOH-d4	-	6.58 s	-	8.09 d (8.5)	6.63 m	-	6.65 d (2.5)	2.67 m	2.67 m
47	MeOH-d3	6.31 d (2.1)	6.41 d (2.1)	-	8.06 s	-	-	6.69 s	2.62–2.69 m	2.62–2.69 m
48	MeOH-d4	6.80 d (2.4)	6.76 d (2.4)	-	8.23 d (9.0)	6.69 dd (9.0, 2.4)	-	7.13 d (2.4)	-	-
49	MeOH-d4	6.83 d (2.4)	6.47 d (2.4)	-	8.30 d (8.4)	7.00 dd (8.4, 3.0)	-	7.13 d (3.0)	-	-
50	MeOH-d4	-	6.76 s	-	8.07 d (9.0)	6.67 dd (9.0, 2.4)	-	7.05 d (2.4)	-	-
51	MeOH-d4	-	6.76 s	-	8.07 d (9.0)	6.67 dd (9.0, 2.4)	-	7.05 d (2.4)	-	-
52	MeOH-d4	-	-	-	8.11 d (8.4)	6.72 dd (8.4, 2.4)	-	7.06 d (2.0)	-	-
53	MeOH-d4	-	-	-	8.11 d (8.4)	6.72 dd (8.4, 2.4)	-	7.06 d (2.0)	-	-
54	MeOH-d4	-	6.83 s	-	8.10 d (8.4)	6.81 d (2.4)	-	-	-	-
55	MeOH-d4	-	6.83 s	-	8.10 d (8.4)	6.81 d (2.4)	-	-	-	-
56	MeOH-d4	-	6.60 s	-	8.37 d (9.0)	7.02 dd (9.0, 2.4)	-	7.01 d (2.4)	-	3.86 d (9.6)
57	MeOH-d4	-	6.60 s	-	8.37 d (9.0)	7.02 dd (9.0, 2.4)	-	7.01 d (2.4)	-	3.86 d (9.6)

2.2. Bibenzyls

Bibenzyls are also abundant in Pleione with a number of 44 (Table 4 & Figure 2) [30], including nine simple bibenzyls (58–66), 23 benzyl substituted bibenzyls (67–89), one bibenzyl and fluorene polymer (85), five bibenzyl and glycoside polymers (91–95), two bibenzyl and phenylpropanoid polymers (96, 97) and four bibenzylamide polymers (98–101). The spectroscopic data of Compound 1–57 are shown in Table 5 and Table 6. The character of bibenzyls is that the carbon-3 (C3), carbon-5 (C5) and carbon-4′(C4′) positions are often hydroxyl or methoxy on the core structure, and the carbon-2 (C2) or/and carbon-4 (C4) often have a p-hydroxyl or phenyl substitution. Two typical structures were isolated from Pleione in 1997 [30]. One was a single structure that mediates an ether combined dihydrophenanthrene with dibenzyl 27, the other was the bibenzyl with two p-hydroxybenzyl groups 76, 77. Another four bibenzyls 67, 68, 78, 79 have only hydroxyl and p-hydroxybenzyl substituents, which is not common in bibenzyl derivatives [23]. It was meaningful to understand such particular structures. Li [28] isolated four pyrrolidone substituted bibenzyl 98–101 from P. bulbocodiodes, which further enriched the chemical compounds of the Pleione species.

Table 4

Bibenzyls from Pleione genus.

No.	Compound	Plant	Reference	No.	Compound	Plant	Reference
58	Batatasin III	B, Y	[17,28]	78	Shancigusin A	Y	[23]
59	3′-O-methylbatatasin III	B, Y	[17,22]	79	Shancigusin B	Y	[23]
60	3, 5-Dimethoxy-3′-hydroxybibenzyl https://scifinder.cas.org/scifinder/view/text/javascript:;	B	[22]	80	Arundin	F	[24]
61	Gigantol	B	[33]	81	5-O-Methylshanciguol	B, Y, F	[23,24,28]
62	Bauhinol C	B	[28]	82	Blestritin B	B	[28]
63	2, 5, 2′, 5′-Tetrahydroxy-3-methoxybibenzyl	B	[28,38]	83	2, 6-bis-(4-hydroxybenzyl)-3′, 5-dimethoxy-3-hydroxybibenzyl	F	[24]
64	2, 5, 2′, 3′-tetrahydroxy-3-methoxybibenzyl	B	[28]	84	Bulbocodin	B	[18]
65	hydroxy-3′,5-dimethxoybibenzyl	Y	[22]	85	Bulbocodin C	B, F	[20]
66	3, 3′-dihydroxy-5-methoxybibenzyl	Y	[22]	86	Bulbocodin D	B	[20,31]
67	Shancigusin C	Y	[23]	87	Pleiobibenzynin A	F	[24]
68	Shancigusin D	Y	[23]	88	Pleiobibenzynin B	F	[24]
69	3, 3′-dihydroxy-2-(p-hydroxybenzyl)-5-methoxybibenzyl	B, Y, F	[18,23,38]	89	6′-(3′′-hydroxyphenethyl)-4′-methoxydiphenl-2, 2′, 5′-triol	B	[39]
70	3′, 5-dihydroxy-2-(p-hydroxybenzyl)-3-methoxybibenzyl	B, Y, F	[18,23,24]	90	2-(4′′-hydroxybenzyl)-3-(3′-hydroxy-phenethyl)-5-methoxy-cyclohexa-2, 5-diene-1, 4-dione	B	[39]
71	Gymconopin D	B	[36,37,40]	91	Batatsin III-3-O-glucoside	B, Y	[17,22]
72	Bulbocol	B, F	[18,24]	92	3′, 5-dimethoxybibenzyl-3-O-β-d-glucopyranoside	B, Y	[17,22]
73	Arundinin	Y, F	[28]	93–94	Shancigusins E-F	Y	[22]
74	Isoarundinin I	B	[28]	95	5-methoxyl bibenzyl-3, 3′-di-O-β-d-glucopyranoside	B	[27]
75	Isoarundinin II	B	[28]	96–97	Shanciols A–B	B	[19]
76	3, 3′-dihydroxy-4-(p-hydroxybenzyl)-5-methoxybibenzyl	B, Y	[18]	98–101	Dusuanlansins A–D	B	[28]
77	Shanciguol	B, Y	[14,23]

Figure 2

The structures of Bibenzyls.

Table 5

13C NMR data of compounds 58–101.

No.	Solvent	Position
		1	2	3	4	5	6	1′	2′	3′	4′	5′	6′	C-α	C-β
58	Acetone-d6	145.1	108.8	159.3	99.7	161.8	106.2	144.3	116.2	158.2	113.6	130.0	120.4	38.6	38.2
59	Chloroform-d	146.5	107.7	156.4	98.8	161.3	106.4	145.1	113.7	159.9	111.5	129.5	120.4	35.8	36.0
60	Chloroform-d	144.1	106.6	160.7	97.9	160.7	106.6	143.7	115.4	155.6	129.5	120.9	112.9	38.0	37.5
61	Acetone-d6	145.1	108.9	159.2	99.7	161.8	106.3	134.1	115.5	148.0	145.2	112.9	121.6	38.0	39.1
62	Chloroform-d	141.8	128.5	128.3	125.9	128.3	128.5	140.7	103.6	154.0	110.0	158.7	108.1	37.8	37.9
63	MeOH-d4	116.9	142.0	159.2	99.4	157.6	108.5	126.1	140.6	113.7	130.2	156.2	115.1	31.9	31.4
65	Chloroform-d	144.0	107.8	158.0	98.8	159.8	105.4	143.2	113.9	160.9	128.8	120.6	111.1	37.6	37.4
67	MeOH-d3	144.0	118.6	157.5	101.4	157.0	108.0	145.0	116.2	158.3	113.7	130.2	120.7	36.5	38.6
68	MeOH-d3	143.9	118.6	157.5	101.3	157.1	108.8	143.4	129.4	129.2	126.7	129.2	129.4	36.6	38.6
69	Acetone-d6	143.6	119.1	157.0	100.1	159.6	107.0	144.5	113.6	158.2	116.1	130.0	120.3	36.2	38.1
70	Acetone-d6	143.2	119.3	159.7	97.8	157.5	109.1	144.5	113.6	158.3	116.1	130.1	120.3	36.0	38.2
71	Chloroform-d	142.4	119.9	155.5	96.5	158.8	105.8	143.8	115.3	158.9	112.8	129.5	120.8	35.2	37.2
72	MeOH-d3	143.7	121.8	161.2	98.1	157.6	109.5	144.9	114.9	160.3	112.6	130.2	120.0	36.4	38.6
73	MeOH-d4	-	-	-	-	-	-	-	-	-	-	-	-	-	-
74	Chloroform-d	142.6	122.2	158.6	106.4	150.8	113.2	142.9	121.3	150.4	119.1	129.1	125.7	36.8	34.8
75	Chloroform-d	142.1	124.3	150.8	102.7	158.4	114.2	143.0	121.3	150.0	119.0	129.1	125.6	36.7	34.5
76	Acetone-d6	141.9	109.9	156.3	114.9	159.3	103.5	144.4	115.4	158.3	113.6	129.9	120.3	38.6	38.4
77	MeOH-d3	145.4	119.1	155.7	101.8	155.7	119.1	142.8	116.1	168.3	113.8	130.2	120.6	33.4	37.7
78	MeOH-d3	142.9	118.9	155.6	101.5	155.6	118.9	134.7	130.1	116.0	156.3	116.0	130.1	33.8	36.9
79	MeOH-d3	142.7	118.9	155.6	101.6	155.6	118.9	143.8	129.3	129.2	126.7	129.2	129.3	33.5	37.7
80	MeOH-d4	142.6	119.5	158.4	98.0	155.9	120.2	143.6	129.1	129.2	126.7	129.2	129.1	33.4	37.7
81	Acetone-d6	142.2	119.9	157.8	98.0	158.3	119.0	144.7	113.6	156.0	115.7	130.1	120.1	33.2	37.2
82	MeOH-d4	143.2	121.8	158.7	98.4	156.2	120.7	135.6	113.3	149.0	145.8	116.3	121.8	34.0	38.2
83	MeOH-d4	142.7	120.3	156.0	98.1	161.0	119.5	145.2	112.6	158.4	114.5	130.2	121.5	37.6	33.3
84	MeOH-d3	142.9	120.4	156.7	98.4	158.5	119.5	131.5	155.9	113.9	116.6	142.8	132.1	34.7	37.9
85	MeOH-d3	144.9	124.4	159.5	120.5	158.3	113.6	141.9	116.4	156.2	113.8	130.2	120.8	29.8	31.6
86	MeOH-d4	145.0	130.6	157.9	120.7	158.3	106.0	140.9	116.5	154.8	113.8	130.2	120.9	29.0	31.4
87	MeOH-d4	140.8	119.4	156.3	98.2	158.4	120.2	142.7	116.5	156.6	113.8	132.0	131.4	31.7	34.6
88	MeOH-d4	140.8	124.9	154.1	121.1	157.7	125.7	145.1	116.0	158.3	113.7	130.1	120.6	33.4	37.7
89	MeOH-d4	143.1	117.6	155.6	99.1	160.0	106.3	144.0	115.0	157.0	112.4	128.9	119.6	36.6	37.1
90	MeOH-d4	143.4	145.3	189.1	108.0	160.1	184.0	144.0	116.3	158.5	114.1	130.4	120.7	30.2	35.6
91	MeOH-d4	144.6	110.6	158.4	102.7	162.2	109.7	145.6	116.6	160.2	114.0	130.3	121.0	38.6	38.6
92	MeOH-d4	144.6	110.5	160.2	102.6	162.1	109.7	145.4	115.4	161.2	112.5	130.3	122.1	38.8	38.8
93	MeOH-d4	144.5	110.4	158.4	102.0	162.2	109.2	145.4	116.5	160.0	113.9	130.3	120.9	38.7	39.1
94	MeOH-d4	145.4	110.3	160.1	101.6	162.0	109.5	143.0	129.6	129.3	126.9	129.3	129.6	39.2	38.7
95	DMSO-d6	143.8	108.9	158.6	99.9	160.2	107.8	143.1	116.5	157.5	113.6	129.2	122.0	37.0	36.7
96	Chloroform-d	143.3	109.5	160.4	100.5	156.6	112.5	144.6	116.5	158.5	113.9	130.4	120.9	35.9	37.8
97	Chloroform-d	143.3	109.4	160.4	100.5	156.6	112.5	144.6	116.1	158.5	114.0	130.4	121.4	35.9	37.8
98	MeOH-d4	143.4	119.5	159.0	101.4	161.1	107.4	144.4	120.9	158.5	114.0	130.3	116.5	36.8	39.7
99	MeOH-d4	143.4	119.5	159.0	101.4	161.1	107.4	144.4	120.9	158.5	114.0	130.3	116.5	36.8	39.7
100	MeOH-d4	144.4	109.8	157.4	114.8	160.2	104.3	144.5	116.4	158.4	113.8	130.2	120.8	39.0	38.7
101	MeOH-d4	144.4	109.8	157.4	114.8	160.2	104.3	144.5	116.4	158.4	113.8	130.2	120.8	39.0	38.7

Table 6

1H NMR data of compounds 58–101.

No.	Solvent	Position
		2	3	4	5	6	2′	3′	4′	5′	6′	H-α	H-β
58	Acetone-d6	6.30 dd (1.8, 1.8)	-	-	-	6.32 dd (1.8, 1.8)	6.71 d (1.8)	-	6.65 dd (7.8, 1.8)	7.07 dd (7.8, 7.8)	6.70 d (7.8)	2.75–2.80 m	2.75–2.80 m
59	Chloroform-d	6.40 t (2.0)	-	6.46 t (2.0)	-	6.23 t (2.0)	-	-	6.72 m	7.08 t (9.0)	6.72 m	-	-
60	Chloroform-d	6.33 m	-	6.31 t (2.5)	-	6.33 m	6.66 m	-	6.66 m	7.15 t (7.5)	6.76 m	2.85 m	2.85 m
61	Acetone-d6	-	-	-	-	6.29 dd (1.8, 1.8)	6.80 d (1.8)	-	-	6.71 d (7.8)	6.65 dd (7.8, 1.8)	2.27–2.59 m	2.27–2.59 m
62	Chloroform-d	7.24 m	7.33 m	7.33 m	7.33 m	7.24 m	6.32 br s	-	-	-	6.36 br s	-	-
63	MeOH-d4	-	-	6.39 d (2.1)	-	6.30 d (2.1)	-	6.62 br s	7.99 d (8.8)	-	6.60 d (2.6)	2.63 br s	2.63 br s
65	Chloroform-d	-	-	6.17 t (1.5)	-	6.23 m	6.71 m	-	6.72 m	7.15 t (8.0)	6.75 m	2.79 m	2.79 m
67	MeOH-d3	-	-	6.23 d (2.0)	-	6.19 d (2.0)	6.55 br s	-	6.57 br d (8.0)	7.03 t (8.0)	6.54 br d (8.0)	2.65–2.69 m	2.52–2.55 m
68	MeOH-d3	-	-	6.17 d (2.4)	-	6.13 d (2.4)	6.98 d (7.2)	7.14 t (7.2)	7.07 t (7.2)	7.14 t (7.2)	6.98 d (7.2)	2.61–2.64 m	2.51–2.55 m
69	Acetone-d6	-	-	6.39 d (1.5)	-	6.36 d (1.5)	6.67 br s	-	6.62 br d (8.0)	7.05 t (8.0)	6.62 br d (8.0)	2.77 m	2.61 m
70	Acetone-d6	-	-	6.39 d (2.0)	-	6.37 d (2.0)	6.65 br s	-	6.61 br d (8.0)	7.05 t (8.0)	6.63 br d (8.0)	2.73 m	2.59 m
71	Chloroform-d	-	-	6.34 d (2.0)	-	6.29 d (2.0)	6.49 br s	-	6.69 m	7.11 t (8.5)	6.64 m	2.79 m	2.65 m
72	MeOH-d3	-	-	6.34 d (2.6)	-	6.27 d (2.6)	6.55 t (2.1)	-	6.69 dd (7.9, 1.7)	7.11 t (7.9)	6.64 m	2.56–2.64 m	2.56–2.64 m
73	MeOH-d4	6.19 d (2.0)				6.25 d (2.0)	6.55 s		6.52 m	6.99 t (8.0)	6.59 dd (8.0, 2.0)	2.71–2.74 m	2.71–2.74 m
74	Chloroform-d	-	-	6.67 d (2.1)	-	6.79 d (2.1)	6.90 d (3.0)	-	6.93 d (8.4)	7.25 t (8.4)	7.16 d (8.4)	2.70 m	2.82 m
75	Chloroform-d	-	-	6.61 d (2.1)	-	6.58 d (2.1)	6.82 br	-	6.97 d (8.2)	7.26 apt t (8.7, 8.1)	6.97 dd	2.73 m	2.85 m
76	Acetone-d6	6.37 s	-	-	-	6.40 s	-	-	6.67 br d (7.2)	7.05 t (7.8)	6.70 br s (8.0)	2.86 m	2.75 m
77	MeOH-d3	-	-	6.39 s	-	-	6.51 t (2.1)	-	6.56 ddd (7.7, 2.6, 1.9)	7.01 t (7.7)	6.47 d (7.7)	2.24–2.30, m	2.24–2.30, m
78	MeOH-d3	-	-	6.32 s	-	-	6.74 d (8.4)	6.57 d (8.4)	-	6.57 d (8.4)	6.74 d (8.4)	2.54–2.57 m	2.16–2.20 m
79	MeOH-d3	-	-	6.34 s	-	-	6.92 d (7.2)	7.13 t (7.2)	7.04 t (7.2)	7.13 t (7.2)	6.92 d (7.2)	2.58–2.62 m	2.24–2.28 m
80	MeOH-d4	-	-	-	-	-	6.97 d (7.0)	7.18 t (7.5)	7.10 t (7.5)	7.18 t (7.5)	6.97 d (7.0)	2.66–2.72 m	2.66–2.72 m
81	Acetone-d6	-	-	6.58 s	-	-	6.64 br s	-	6.61 m	7.04 t (8.0)	6.58 m	2.74 m	2.37 m
82	MeOH-d4	-	-	6.48 s	-	-	6.38 d (1.8)	-	-	6.60–6.65 m	6.44 dd (8.0, 1.8)	2.61–2.71 m	2.30–2.40 m
83	MeOH-d4	-	-	6.49–7.15 m	-	-	6.49–7.15 m	-	-	6.49–7.15	-	2.23–2.37 m	2.64–2.73 m
84	MeOH-d3	-	-	6.45 s	-	-	-	6.57 d (8.2)	6.53 dd (8.2, 3.3)	-	6.58 d (3.3)	2.43–2.46 m	2.43–2.46 m
85	MeOH-d3	-	-		-	6.56 s	6.50 s		6.57 dd (8.4, 2.2)	7.01 t (8.4)	6.50 m	2.59–2.66 m	2.59–2.66 m
86	MeOH-d4	-	-	-	-	6.33 s	6.53 m	-	6.57 dd (8.2, 2.3)	7.02 t (8.2)	6.53 m	2.59–2.77 m	2.59–2.77 m
87	MeOH-d4	-	-	6.46 s	-	-	6.57 d (2.0)	-	6.51 dd (8.5, 2.0)	6.77 d (8.5)	-	2.66 m	2.42 m
88	MeOH-d4	-	-	-	-	-	6.47 dd (2.1, 2.0)	-	6.55 ddd (8.0, 2.1, 2.0)	7.00 t (8.0)	6.46 ddd (8.0, 2.1, 2.0)	2.67 m	2.35 m
89	MeOH-d4	-	-	6.33 m	-	6.34 m	6.41 m	-	6.52 m	6.96 t (8.0)	6.39 m	2.56 m	2.56 m
90	MeOH-d4	-	-	6.02 s	-		6.59 m	-	6.62 m	7.06 t (8.0)	6.58 m	2.75 m	2.46 m
91	MeOH-d4	6.52 t (2.0)	-	6.51 t (2.0)	-	6.40 t (2.0)	6.59 t (2.0)	-	6.61 dd (7.5, 2.8)	7.05 t (7.7)	6.63 br d (7.7)	2.83 m	2.83 m
92	MeOH-d4	6.52 t (2.0)	-	6.50 t (2.0)	-	6.40 t (2.0)	6.70 br d (1.7)	-	6.73 dd (8.6, 7.7)	7.14 t (8.6)	6.74 br d (7.7)	2.84 m	2.84 m
93	MeOH-d4	6.41 m	-	6.40 m	-	6.35 br s	6.54 m	-	6.54 m	7.00 br t (7.8)	6.57 d (7.8)	2.71–2.81	2.71–2.81
94	MeOH-d4	6.51 m	-	6.51 m	-	6.39 s	7.15 m	7.24 t (7.5)	7.15 m	7.24 t (7.5)	7.15 m	2.83–2.91	2.83–2.91
95	DMSO-d6	6.51 br s	-	6.45 br s	-	6.44 br s	6.92 br s	-	6.86 br d (7.8)	7.18 t (7.8)	6.87 br d (7.8)	2.81 m	2.81 m
96	Chloroform-d	6.37 d (2.6)	-	6.31 d (2.6)	-	-	6.61 m	-	6.61 m	7.05 t (7.7)	6.63 d (7.7)	2.80 m	2.80 m
97	Chloroform-d	6.36 d (2.6)	-	6.29 d (2.6)	-	-	6.61 m	-	6.61 m	7.05 t (7.7)	6.64 d (7.7)	2.79 m	2.79 m
98	MeOH-d4	-	-	6.25 d (2.5)	-	6.22 d (2.5)	6.60 br s	-	6.61 m	7.07 t (7.5)	6.62 d (7.5)	2.94 m	2.76 m
99	MeOH-d4	-	-	6.25 d (2.5)	-	6.22 d (2.5)	6.60 br s	-	6.61 m	7.07 t (7.5)	6.62 d (7.5)	2.94 m	2.76 m
100	MeOH-d4	6.28 br s	-	-	-	6.27 br s	6.59 d (2.5)	-	6.57 m	7.07 t (7.5)	6.64 d (7.5)	2.76–2.81 m	2.76–2.81 m
101	MeOH-d4	6.28 br s	-	-	-	6.27 br s	6.59 d (2.5)	-	6.57 m	7.07 t (7.5)	6.64 d (7.5)	2.76–2.81 m	2.76–2.81 m

2.3. Glucosyloxybenzyl Succinate Derivatives

The Pleione is also rich in glucosyloxybenzyl succinate derivatives [41]. The succinic acid is the basic structure and it often combines with saccharides to form glycosides (102–124) (Table 7 and Figure 3). The biological studies indicated that the glucosyloxybenzyl succinate derivatives compounds were documented to exert significant activities against delaying aging and improving learning and memory ability of aging mice [42]. Cui [43] used the succinic acid derivatives as an indicator compound for High Performance Liquid Chromatography (HPLC) content determination. The result indicated that the 117 and 118 can be used to distinguish three sources of TCM shan-ci-gu. Lv [44] established the HPLC fingerprint analysis of the P. bulbocodioides via measuring the content of the indicator compound 117. The similar values in the ten producing areas were all more than 0.980 of Chinese medicine. The relative retention time (in the fingerprints was similar, but the Relative Standard Deviation (RSD) values of the relative peak areas were quite different. This was assumed to be the effects of the wild environment and growth years. On account of the difficulty to obtain high-polarity compounds 117, 118, 123 and 145, Wang [45] developed a rapid and efficient method Elution-extrusion Counter-current Chromatography Separation (EECCC): the solvent system composed of n-butanol, ethanol and water with a volume ratio of 20:1:20. The upper phase was stationary phase, the lower phase was mobile phase at a flow rate of 1.5 mL·min−1, with a rotation speed of 850 rpm at temperature of 35 °C. Five high-polarity compounds were extracted in 371 min simultaneously by this method. The other four kinds of acids, the glucosyloxybenzyl succinate derivatives Pleionosides A–J (102–111) connected, are (2R)-2-p-hydroxybenzylmalic acid (102–105), (2R)-2-benzylmalic acid (106), (2R, 3S)-2-benzyl tartaric acid (107) and (2R)-2-isobutylmatic (108–110). Their properties confirmed that they could support further chemotaxonomic researches in Orchidaceae as the specialized metabolites [27].

Table 7

Glucosyloxybenzyl succinate derivatives from Pleione genus.

No.	Compound	Plant	Reference	No.	Compound	Plant	Reference
102–111	Pleionosides A–J	B	[27]	118	Dactylorhin A	B, Y	[22,27]
112	Vandateroside II	B	[27]	119	(−)-(2R,3R)-1-(4-O-β-d-glucopyranosyloxybenzyl)-4-methyl-2-isobutyltartrate	B	[27]
113	Grammatophylloside B	B	[27]	120	Loroglossin	B	[27]
114	Grammatophylloside A	B	[27]	121	(−)-(2S)-1-[(4-O-β-d-glucopyranosyloxy) benzyl]-2-isopropyl-4-[(4-O-β-d-glucopyranosyloxy)benzyl] malate	B	[27]
115	Cronupapine	B	[27]	122–123	Shancigusins H-I	Y	[22]
116	Gymnoside I	B, Y	[22,27]	124	Bletillin A	B	[28]
117	Militarine	B	[27,28]

Figure 3

The structures of Glucosyloxybenzyl succinate derivatives.

2.4. Other Compounds

Other compounds consist of seven flavones (125–131), eight lignans (132–139) and 44 others (140–183) (Table 8 & Figure 4). The flavones contained three simple flavones (125–127), two prenylated flavones (128, 129) and two biflavonoids (130, 131). The lignans consist of three simple lignans (132–134) and five tetrahydrofuran lignans (135–139). Yuan [40] isolated biflavonoids 131 from Pleione for the first time in 2012. Li [16] isolated two isomerized lignan compounds 132 and 133 from P. bulbocodioides in 1997. The pseudobulbs of P. formosana have been used as one of the substitute of Shan-ci-gu [46,47]. However no phytochemical investigation was performed on it. Thus, Shiao [24] began the chemical research in 2009 and it was the first time to isolate the cycloartane triterpenoid compound 167 from the natural product. Yang [48] analyzed the chemical compounds of the P. bulbocodiodes, P. yunnanensis and P. limprichtii from fifteen producing areas by High Performance Liquid Chromatography Diode Array Detection (HPLC-DAD). The Cluster Analysis and Principal Component Analysis were used for quality evaluation, but the compounds corresponding to the chromatographic peak were not determined.

Table 8

Other compounds from Pleione genus.

No.	Compound	Plant	Reference	No.	Compound	Plant	Reference
125	5, 7-dihydroxy-8-methoxyflavone	B	[38]	155	3-hydroxybenzoic acid	B	[49]
126	Isorhamnetin-3, 7-di-O-β-d-glucopyranoside	B	[29]	156	Methyl 3-(3-hydroxyphenyl)Propionate	B	[31]
127	3′-O-methylquercetin-3-O-β-d-gluCopyranoside	B	[29]	157	4-(4′′-hydroxybenzyl)-3-(3′-hydroxy-phenethyl) furan	B, Y	[49]
128	3, 5, 7, 3′-tetrahydroxy-8, 4′-dimethoxy-6-(3-methylbut-2-enyl)flavone	B	[29]	158	Methyl 3-(4-hydroxyphenyl)propionate	B	[1]
129	3, 5, 3′-trihydroxy-8, 4′-dimethoxy-7-(3-methylbut-2-enyloxy) Flavone	B	[29]	159	3-(3′-hydroxyphenethyl)furan-2(5H)-one	B	[49]
130	Kayaflavone	B	[40]	160	Ergosta-4, 6, 8(14), 22-tetraen-3-one	B	[33]
131	5, 5′′, 7, 4′, 4′′′, 7′′-hexadroxy-[3′-8′′]Biflavone	B	[40]	161	Tetracosanol	Y	[26]
132–133	Sanjidin A-B	B	[16,40]	162	(E)-ferulic acid hexacosyl ester	Y	[34]
134	Phillygenin	B	[38]	163	(Z)-ferulic acid hexacosyl ester	Y	[34]
135	Epipinoresinol	B	[22]	164	Gallicacid	Y	[26]
136	Syringaresinol	B, Y	[22,33]	165	5-hydroxymethylfurfural	B	[31]
137	Syringaresinol Mono-O-β-d-glucoside	B	[27]	166	Methyl 3-(3′-hydroxyphenethyl)furan-2(5H)-one	B	[49]
138	Lirioresinol	B	[29]	167	(24R)-cyclomargenyl p-coumarate	F	[24]
139	(E)-p-hydroxycinnamic acid	Y	[45]	168	(24R)-cyclomargeno	F	[24]
140	(7S, 8R)-dehydrodiconiferyl alcohol-9′-O-β-d-glucopyranoside	B	[27]	169	Tetacosanoic acid-2, 3-dihydroxypropyl ester	Y	[26]
141	Pleionin	B	[16]	170	Hydroquinone	B	[40]
142	Pleionol	B	[18]	171	β-sitosterol	B, Y	[22,31]
143	Gastrodioside	B	[29]	172	β-daucosterol	Y	[34]
144	Phenl-β-d-glucopyranoside	B	[29]	173	Methyl 4-hydroxyphenylacetate	Y	[40]
145	Gastrodin	B	[27,45]	174	Daucostero	B, Y	[22]
146	(E)-ferulic acid	Y	[34]	175	Physcion	B	[40]
147	Cinnamic acid	B	[1]	176	Chrysophanol	B	[26]
148	p-hydroxybenzoic acid	B, Y	[39,40]	177	4, 4′-dihydroxydiphenylmethane	B	[38]
149	p-hydroxybenzaldehyde	B	[39,40]	178	4-oxopentanoic	B	[1]
150	Methy (4-OH) phenylacetate	B	[25]	179	Monopalmttin	Y	[26]
151	4-(ethoxymethyl)phenol	B	[1]	180	Amber Acid	Y	[22]
152	4-(methoxymethyl)phenol	B	[1]	181	Adenosine	Y	[22]
153	p-dihydroxy benzene	B	[35,37]	182	Pholidotin	Y	[34]
154	3-hydroxybenzenepropanoic acid	B	[45]	183	Triphyllol	Y	[34]

Figure 4

The structures of other compounds.

3. Biological Activities

Previous studies showed that the compounds extracted from P. bulbocodiodes, P. yunnanensis and P. formosana exerted anti-tumor, anti-neurodegenerative, anti-inflammatory anti-oxidation activities. That is why Pleione has been gaining increasing attention. The Pleione’s biological activities are tightly related to the traditional efficacy of “curing fever, detoxifying the body, mitigating the swelling and cleaning the blood stasis” in Chinese Pharmacopoeia [13]. Research on biological activities will establish a foundation for the further pharmacological researches and enlighten the drug discovery for anti-tumor usage.

3.1. Anti-Tumor Activity

The biological activities of Pleione can be attributed primarily to the phenanthrenes and bibenzyls. Among those activities, that against tumors was the most significant. Liu [37] proved that the ethyl acetate extract of P. bulbocodiodes had a certain inhibitory effect on mice cancer cells LA795, while the petroleum ether extract only had an inhibition rate of 75.58% at 800 μg·mL−1, but no remarkable inhibition at 400 μg·mL−1 and below. However, the n-butanol extract did not exert inhibitory at all. This result laid the foundation for the later chemical compounds study, and regarded the ethyl acetate as key fraction for research. The compounds such as 26, 34, 44, 58, 60 and 153 were demonstrated certain inhibitory effects against LA795 at 100 μg·mL−1. Liu [37] confirmed that 34 and 153 showed the cytotoxic activity against LA795 cells with IC50 value of 66 and 12 μg·mL−1. Compound 58 exhibited cytotoxic activity and anti-allergic activity. Wang [33] found that the bibenzyls 58 and 61 isolated from P. bulbocodiodes significantly inhibited the growth of leukemia cells K562, HL-60, liver cancer cells BEL-7402, gastric cancer cells SGC-7901, lung cancer cells A569 [50], H460 and melanoma cells M14. Wang’s group [32,34] indicated that 58 isolated from P. yunnanensis, performed strong activity against the growth of LA795 cells with IC50 value of 76.21 μM, but only moderate inhibition against A569 cells and BEL-7402 cells. Compound 40 was shown to exert moderate cytotoxic activity against A569 cells. Compound 48 was proved significant cytotoxic activity against cancer cells at 10−6 M. Compound 49 exerted cytotoxic activities against colon cancer cells HepG2, liver cancer cells BGC-823 and breast cancer cells MCF-7 with IC50 values of 8.3, 2.3 and 2.5 μM, respectively [32]. Compound 56 exerted moderate activities in colon cancer cells HCT-116, HepG2 cells and MCF-7 cells with IC50 values of 8.1, 8.4 and 3.9 μM, respectively. It suggested that the stereochemistry of 9(10)H-phenanthren-10(9)-one is of great significance to the cytotoxic activity. Tumor cell invasion and metastasis determined the prognosis of cancer patients [51]. In a word, a number of studies confirmed that the compounds isolated from the Pleione have an optimistic effect on anti-tumor treatment.

3.2. Anti-Neurodegenerative Activity

Glycosides were found to inhibit the proliferation of tumor cells, which is meaningful for anti-tumor therapy [52]. The glucosyloxybenzyls were subjected to evaluation for learning and memory deficits of mice caused via scopolamine and D-Gal + NaNO2 [53]. Zhang [54] discussed that the Dactylorhin B, 117, 118 and 120 isolated from Coeloglossum viride var. bractestum were demonstrated to exert activities of anti-apoptosis, promoting intelligence and delaying aging. The P. bulbocodiodes consists of the three components mentioned above, except Dactylorhin B [27]. 145 was documented to exhibit activities of neuroprotective, neurasthenia and epilepsy [55]. 29 and 58 performed certain neurotoxic activities of mice hippocampal neurons (SY-SH-5Y) at 10−5 M [25]. In addition, 2, 32 and 39 indicated significant neurotoxic activity at 10−5 M [45]. Han [27] reported the hepatoprotective activity of glucocopyloxybenzyl succinate derivatives for the first time in 2019. These neuroprotective effects may be related to the management of antioxidants, malondialdehyde (MDA), glutathione (GSH) levels as well as the improvement of adenosine triphosphatase (ATPase) [56]. The active metabolite of APAP was reported to deplete the glutathione and initiate mitochondrial oxidative stress. Moreover, the reactive oxygen species (ROS) produced during the latter process would destroy the normal function of the mitochondria, ultimately leading to the death of necrotic cell [57,58,59]. These studies fully clarified the pharmacodynamic basis of the Pleione and laid a material foundation for anti-dementia activity.

3.3. Anti-Inflammatory and Anti-Oxidation Activity

Some compounds of Pleione exert activities of anti-bacterial and anti-inflammatory (Table 9). Wang [25,33] illustrated that 1 significantly inhibited NO production in mice peritoneal macrophages at 10−5 M. Compounds 1 and 3 had strong inhibition activity on NO production. Compounds 3 and 61 showed good performance in calmodulin inhibition and antifungal action. Li [28,29] suggested that the compounds of 4, 63 and 64 significantly inhibited NO production induced via LPS in BV-2 cells with IC50 values of 5.44, 2.46 and 3.14 μM, respectively. They may be the promising compounds for the development of anti-inflammatory drugs. However 9, 25, 26, 58, 62, 73, 74, 75, 81, 82, 86 and 117 only exhibited moderate inhibition on NO production. Liu [49] suggested that 170 was documented to have strong activities of anti-cytotoxicity and anti-bacterial.

Table 9

The LPS-stimulated NO production of BV-2 microglail cells.

No.	IC50 (μM)	No.	IC50 (μM)
1	2.35	82	21.0
2	1.74	86	21.8
63	2.46	81	26.1
64	3.14	14	14.4
58	50.2	12	24.5
62	38.0	26	13.1
75	23.2	10	17.7
74	17.5	25	23.4
73	56.7	117	59.2

3.4. Others

In addition to the anti-tumor, anti-neurodegenerative, anti-inflammatory and anti-oxidation activities, the Pleione also exhibited activities of inhibiting antigen-induced degranulation, free radical scavenging as well as anti-oxidant. Wang [26,34] proved that 58, 69, 70, 76 and 81 were shown the activity of antigen-induced degranulation in RBL-2H3 cells [60]. The inhibition efficiency of 58, 69 and 70 was between 65.5% and 99.4%.

4. Conclusions

The chemical investigation of the Pleione has attracted much attention around the world and some breakthrough progress has been made. Up to now, the family of the compounds had become more and more abundant, especially 9(10)H-phenanthren-10(9). This can not only provide significant evolutionary and chemotaxonomic knowledge of the genus Pleione, but also enlighten the further development and utilization of new drugs.

The future important focal points on the Pleione researches are summarized as follows. Firstly, the research range of species of the genuns Pleione need to be widened except for the P. bulbocodioides, P. yunnanensis and P. formosana in order to seek for novel substitutes. The mechanism of the biological activity should be figured out to shine more clear therapy pattern. Secondly, water-soluble and fat-soluble extracts are necessary to be explored. Thirdly, research needs further progress for clinical application to serve for the patients. Lastly, there needs to be immediate scientific protection for Pleione plants because of their endangered status.