13C-NMR data of diterpenes isolated from Aristolochia Species.

The genus Aristolochia,an important source of physiologically active compounds that belong to different chemical classes, is the subject of research in numerous pharmacological and chemical studies. This genus contains a large number of terpenoid compounds, particularly diterpenes. This work presents a compilation of the 13C-NMR data of 57 diterpenoids described between 1981 and 2007 which were isolated from Aristolochia species. The compounds are arranged skeletonwise in each section, according to their structures, i.e., clerodane, labdane, and kaurane derivatives. A brief discussion on the 13C chemical shifts of these diterpenes is also included.

Introduction

The genus Aristolochia (Aristolochiaceae) consists of about 500 species mostly distributed along tropical, subtropical, and Mediterranean regions of the world [1,2,3]. The Aristolochia species are cultivated as ornamentals [4] and popularly used as sources of abortifacient, emmenagogue [5,6], sedative [7], analgesic, anticancer, anti-inflammatory, antifeedant [8], muscle relaxant [9], antihistaminic, and antiallergic [10] drugs, for intestinal worms, in the treatment of cholera, stomach ache, abdominal pain, rheumatism [11], malaria [12], wounds and skin diseases [13], and also useful in treatment of different types of poisonous bites and stings [14,15]. Several other biological properties have been described [16]. On the other hand, consumption of many plants of the genus can lead to progressive nephrophathy and urothelial cancer in humans [17,18]. As a consequence, the distribution of herbal medicines containing Aristolochia extracts are prohibited in many countries due to their nephrotoxic, carcinogenic, and mutagenic properties [1].

Aristolochic acids have been frequently found in Aristolochia species [19]. These compounds show toxic effects at the renal level and carcinogenic properties [20,21]. Phytochemical investigations of these species revealed both the presence of aporphinic, tetrahydroprotoberberinic, benzyltetra-hydroisoquinolinic, and bisbenzyltetrahydroisoquinolinic alkaloids [22] and other nitrogenated derivatives (phenantrenoids, aristolactams, and porphyrins) [23,24,25]. Quinones, coumarins, flavanoids, lignoids (phenylpropanoids, neolignans, and lignans), and fatty acids are frequently isolated from plants of the genus [26]. However, the most prominent compounds in Aristolochia are terpenoids, constituents of the essential oils isolated from the plant species. The majority of the identified terpenoids are kaurane, clerodane, and labdane diterpene derivatives (Figure 1).

Figure 1

Diterpene classes present in Aristolochia species.

The review “Terpenoids of Aristolochia and their biological activities”, which covered the literature up to 2003, lists 52 diterpenoids isolated from the genus and their pharmacological properties [16]. In the present review a new comprehensive coverage of diterpenes isolated from Aristolochia species up to this moment (Table 1, Table 2 and Table 3) is described, broadly covering 26 kauranes (Figure 2 and Figure 3), 29 clerodanes (Figure 4 and Figure 5), one furanoditerpene derivative (Figure 6), and 9 labdanes (Figure 7). Moreover, the 13C-NMR data of these compounds are also compiled (Table 4 and Table 5). For some structures no 13C-NMR data was found in the investigated literature and there is disagreement concerning the 13C-NMR data of (–)-11-hydroxykaur-16-en-19-oic acid. Sometimes different structures were given the same names.

Table 1

Kaurane diterpenoids isolated from Aristolochia species.

Clerodane	Species
ent-Kauran-16β-ol [(–)-kauranol] (1)	A. rodriguesii [28]
ent-16β(H)-Kauran-17-oic acid (2)	A. elegans [7]; A. triangularis [13]
ent-Kauran-16β,17-diol (3)	A. elegans [7]; A. pubescens [31]; A. triangularis [13]
ent-16β(H)-Kaurane (4)	A. elegans [7]; A. triangularis [13]
ent-16α(H)-Kauran-17-al (5)	A. elegans [7]
ent-Kauran-16β,19-diol [ent-16β,19-dihydroxykaurane] (6)	A. rodriguesii [28]
ent-16α-Hydroxy-kauran-19-al [16a-hydroxy-(–)-kauran-19-al] (7)	A. rodriguesii [28]; A. triangularis [32]
ent-16β,17-Dihydroxy-(–)-kauran-19-oic acid (8)	A. rodriguesii [28]
ent-16β-Hydroxy-kauran-18-al [(–)-kauran-16α-hydroxy-18-al] (9)	A. triangularis [26]
ent-16β,17-Epoxykaurane (10)	A. elegans [7]; A. triangularis [32]
ent-15β,16β-Epoxy-17-hydroxy-kauran-19-oic acid (11)	A. rodriguesii [28]
ent-15β,16β-Epoxykauran-17-ol (12)	A. triangularis [13]
ent-16β,17-Isopropylidenedioxy-(–)-19-oic acid (13)	A. rodriguesii [28]
17-nor-(–)-Kauran-16-one (14)	A. triangularis [13]
ent-17-Hydroxy-kaur-15-en-19-oic acid (15)	A. rodriguesii [28]
ent-Kaur-15-en-17-ol (16)	A. elegans [7]; A. pubescens [31]; A. triangularis [13,32]
ent-11β-Hydroxy-kaur-16-en-19-oic acid [(–)-11-hydroxy-kaur-16-en-19-oic acid] (17)	A. anguicida [33]
ent-Kaur-16-en-19-oic acid [kaurenic acid] (18)	A. anguicida [33]; A. rodriguesii [28]; A. triangularis [13]
(–)-ent-Kaur-16-ene (19)	A. triangularis [13,32]
(–)-ent-Kaur-16-en-19-ol (20)	A. triangularis [13,32]
(–)-ent-Kaur-16-en-19-al (21)	A. triangularis [13,32]
ent-7β-Hydroxy-kaur-16-en-19-oic acid (22)	A. anguicida [34]
ent-Kaur-16-en-3β,19-diol [ent-3β,18-dihydroxykaur-16-ene] (23)	A. rodriguesii [28]
ent-16β-Hydroxy-17-kauranyl aristolachate I [aristoloin I] (24)	A. elegans [4]
ent-16β-Hydroxy-17-kauranyl aristolachate II [aristoloin II] (25)	A. pubescens [31]
ent-17-Hydroxy-16β-kauranyl aristolachate I [aristolin] (26)	A. elegans [4]

Usual names are given in brackets

Table 2

Clerodane diterpenoids isolated from Aristolochia species.

Clerodane	Species
(5R,8R,9S,10R)-ent-3-Cleroden-15-oic acid [13,14-dihydrokolavenic acid; populifolic acid] (27)	A. brasilienses [38]; A. cymbifera [39]; A. galeata [40]
(5R,8R,9S,10R)-ent-3-Cleroden-15-ol [dihydrokolavenol] (28)	A. galeata [40]
(5R,8R,9S,10R)-ent-15-Ethanoyl-3-clerodene [dihydrokolavenol acetate] (29)	A. galeata [40]
Methyl (5R,8R,9S,10R)-ent-3-cleroden-15-oate [methyl populifoloate]) (30)	A. esperanzae [38]; A. galeata [40]
(5S,8R,9S,10R)-ent-3-Cleroden-15-oic acid [epi-populifolic acid] (31)	A. cymbifera [39]
Methyl (5S,8R,9S,10R)-ent-3-cleroden-15-oate (32)	A. cymbifera [39]
(5R,8R,9S,10R)-ent-Clerod-3,13-dien-15-oic acid [Δ13,14-kolavenic acid] (33)	A. brasilienses [38]; A. galeata [40]
(5R,8R,9S,10R)-ent-Clerod-3,13-dien-15-ol [Δ13,14-kolavenol] (34)	A. galeata [40]
(5R,8R,9S,10R)-ent-15-Ethanoyl-clerod-3,13-diene [acetyl kolavenoate] (35)	A. galeata [40]
Methyl (5R,8R,9S,10R)-ent-clerod-3,13-dien-15-oate [methyl kolavenoate] (36)	A. esperanzae [38]; A. galeata [40]
(5S,8R,9S,10R)-ent-Clerod-3,13-dien-15-oic acid (37)	A. brasilienses [38]
(5R,8R,9S,10R)-ent-Clerod-3,14-dien-13β-ol [(+)-kolavelool] (38)	A. galeata [40]
(5R,8R,9S,10R)-(4→2)-abeo-Clerod-13β-hydroxy-2,14-dien-3-oic acid [(+)-(4®2)-abeo-kolavelool-3-oic acid] (39)	A. chamissonis [41]
(5R,8R,9S,10R)-ent-Clerod-14-en-3β,4α,13α-triol [(–)-3α,4β-dihydroxykolavelool] (40)	A. chamissonis [41]
(5R,8R,9S,10R)-ent-Clerod-3,14-dien-13α-ol [(–)-kolavelool] (41)	A. chamissonis [41]; A. cymbifera [38]; A. galeata [38]
(5R,8R,9S,10R)-ent-Clerod-3,14-dien-2α,13α-diol [(–)-2β-hydroxykolavelool] (42)	A. chamissonis [41]
(5R,8R,9S,10R)-ent-Clerod-3,14-dien-2β,13α-diol [(+)-13-epi-2α-hydroxykolavelool; 13-epi-roseostachenol] (43)	A. chamissonis [41]
(5S,8R,9S,10R)-2-Oxo-ent-3-cleroden-15-oic acid (44)	A. brasilienses [38]
(5R,8R,9S,10R)-2-Oxo-ent-3-cleroden-15-oic acid [2-oxopopulifolic acid] (45)	A. brasilienses [39]; A. cymbifera [39]; A. galeata [40]
(5R,8R,9S,10R)-2-Oxo-ent-15-ethanoyl-3-clerodene [2-oxodihydrokolavenol acetate] (46)	A. galeata [40]
Methyl (5R,8R,9S,10R)-2-oxo-ent-3-cleroden-15-oate [methyl 2-oxopopulifoloate] (47)	A. esperanzae [38]
(5R,8R,9S,10R)-2-Oxo-ent-clerod-3,14-dien-13α-ol [(–)-13-epi-2-oxokolavelool; 13-epi-roseostachenone] (48)	A. chamissonis [41]
Methyl (5S,8R,9S,10R)-2-oxo-ent-clerod-3,13-dien-15-oate (49)	A. brasilienses [38]
(5R,8R,9S,10R)-2-Oxo-ent-clerod 3,13-dien-15-oic acid [Δ13,14-2-oxokolavenic acid] (50)	A. brasilienses [38]
Methyl (5R,8R,9S,10R)-2-oxo-ent-clerod-3,13-dien-15-oate [methyl Δ13,14-2-oxokolavenoate] (51)	A. esperanzae [38]
(5S,8S,9R,10S)-2-Oxo-ent-clerod-3,13-dien-15-oic acid (52)	A. brasilienses [38]
Methyl (5R,8R,9S,10R)-ent-2α-hydroperoxy-3-cleroden-15-oate (53)	A. esperanzae [38]
(5R,8R,9S,10R)-ent-2α-Hydroperoxy-clerod-3,14-dien-13α-ol [(–)-2β-hydroperoxykolavelool] (54)	A. chamissonis [41]
Methyl (5R,8R,9S,10R)-ent-2α-hydroperoxy-clerod-3,13-dien-15-oate (55)	A. esperanzae [38]

Usual names are given in brackets

Table 3

Labdane diterpenoids isolated from Aristolochia species.

Clerodane	Species
(5R,8R,9S,10S)-ent-Labdan-8β-hydroxy-15-oic acid (57)	A. galeata [40]
(5R,8R,9S,10S)-ent-Labd-13-en-8β-hydroxy-15-oic acid [Δ13,14-ent-labd-8β-ol-15-oic acid] (58)	A. galeata [40]
(5R,8R,9S,10S)-ent-Labd-14-en-8β-ol (60)	A. cymbifera [40]
(5S,8R,9R,10R)-ent-Labd-14-en-8β,13α-diol (61)	not isolated from Aristolochia species [54]
(5R,9S,10S)-ent-Labd-8(17)-en-15-oic acid (62)	A. ringens [55]
(5R,9S,10S)-ent-Labd-8(17),13-dien-15-oic acid [copalic acid] (63)	A. esperanzae [40]; A. galeata [40]
(5R,9S,10S)-ent-Labd-6β-hydroxy-8(17),13-dien-15-oic acid (64)	A. esperanzae [40]
Methyl (5R,8R,9S,10S)-ent-labd-8(17),13-dien-15-oate [methyl copalate] (65)	A. esperanzae [40]
Methyl (5R,9S,10S)-ent-labd-6β-hydroxy-8(17),13-dien-15-oate (66)	A. esperanzae [40]
(5R,10S)-ent-Labd-8,14-diene (67)	A. cymbifera [40]

Usual names are given in brackets

Figure 2

Kaurane diterpenoids isolated from Aristolochia species.

Figure 3

Substituted kaurane diterpenoids isolated from Aristolochia species.

Figure 4

Clerodane diterpenoids isolated from Aristolochia species.

Figure 5

Clerodane diterpenoids isolated from Aristolochia species, showing oxygened C-2.

Figure 6

Furanoditerpene isolated from Aristolochia species.

Figure 7

Labdane diterpenoids isolated from Aristolochia species.

Table 4

13C-NMR data (in CDCl3) of diterpenes from Aristolochia species.

Carbon	Compound / δC (in ppm)
	1 [56]	2 [13]	3 [31]	4 [13]	6 [28]	8 [57,58]	10 [59]	11 [28]	12 [13]	13 [28]	14 [56]	15 [28]	16 [13]	17 [33]	18 [33]
1	42.0	39.2	40.3	40.9	40.35	41.1	40.4	39.82	40.4	40.66	41.0	40.73	42.0	39.10	41.13
2	18.6	18.2	18.6	18.6	17.97a	19.8	18.6	18.39a	18.7	19.06	18.5	19.05a	18.6	20.07	19.52
3	42.0	42.0	41.9	42.0	35.55	38.7	42.0	34.33	42.1	38.39	41.9	38.03	43.8	35.00	38.23
4	33.2	33.1	33.2	33.6	38.50	43.9	33.2	48.47	33.3	43.66	33.2	43.55	33.2	43.60	44.66
5	56.2	56.1a	56.2	56.1a	56.90b	57.0	56.2	56.68b	55.9	56.96	56.1	56.65	55.8	49.80	57.49
6	20.4	20.6	20.4	20.7	20.49	23.0	20.2	20.10	19.3	22.00	19.2	20.70	19.2	19.51	22.28
7	40.3	40.3	42.0	40.4	42.31	42.8	41.1	42.02	32.5	41.52	40.3	39.24	39.2	40.84	41.71
8	45.3	45.3	44.7	45.1	45.17	45.0	45.4	45.20	43.4	44.51	42.5	48.81	48.8	47.63	44.17
9	56.8	56.0a	56.7	56.0a	56.70b	56.3	55.9	55.20b	50.8	55.40	55.0	47.57	48.3	47.89	55.55
10	39.3	38.0	39.4	39.2	39.15	40.1	39.3	39.44	39.2	39.64	39.4	39.72	39.4	40.00	40.09
11	18.0	18.5	18.3	18.3	17.93a	19.0	19.3	18.13a	18.2	19.06	18.5	18.75a	18.6	77.52	18.43
12	26.9	31.2	26.3	31.3	26.06	26.8	29.2	26.90	27.0	27.06	29.7	25.31	25.6	33.97	33.53
13	49.0	44.7	45.5	41.4	48.64	45.9	42.7	48.93	36.0	45.64	47.9	40.92	41.1	44.41	44.28
14	37.7	40.8	37.3	38.1	37.36	37.8	38.6	37.81	36.0	37.88	37.5	43.71	40.4	39.79	40.13
15	58.0	45.0	53.4	44.7	57.66	53.9	48.9	57.80	65.7	55.54	55.2	135.39	135.7	47.41	49.39
16	79.4	55.9	81.9	45.9	79.16	81.7	66.4	79.29	69.5	89.16	222.5	145.82	145.6	155.24	156.32
17	24.5	182.5	66.4	14.8	24.05	66.5	50.4	24.47c	59.9	70.05	-	60.63	61.1	104.09	103.69
18	33.5	33.5	33.5	33.2	26.89	29.3	33.6	24.26c	33.6	28.93	33.6	28.87	35.5	30.08	29.38
19	21.6	21.5	21.5	21.6	64.98	180.1	21.6	205.80	21.6	182.64	21.7	180.90	21.5	184.05	184.00
20	18.0	17.3	17.8	17.4	18.11	16.0	17.8	16.40	17.5	15.74	18.0	15.25	17.6	15.93	16.02
1’										108.39
2’										26.81
3’										26.91
Carbon	Compound / δC (in ppm)
	19 [56]	20 [57](?)	22 [34]	22 [34] (P)	22 [34](D)	23 [60]	27 [26]	27 [34]	29 [61]	30 [38]	30 [38]	31 [39]	32 [39]	33 [38]	33 [39]
1	41.3	40.5	39.79	40.9	40.3	38.7	18.3	17.4	17.3	17.5	18.2	17.7	17.6	17.3	18.3
2	18.7	18.3	20.07	19.7	19.0	27.6	26.8	27.6	27.5	27.1	26.8	24.1	24.0	27.5	26.9
3	42.0	35.7	40.84	38.5	37.9	80.6	120.5	120.6	120.4	120.0	120.4	123.2	123.1	120.5	120.4
4	33.3	39.3	43.60	43.7	42.5	42.7	144.5	144.4	144.4	143.7	144.4	139.9	139.9	144.5	144.4
5	56.1	56.9	49.80	49.5	46.3	55.8	38.2	38.3a	38.3	38.0a	38.4	38.5	38.2	38.3a	38.2
6	20.3	20.5	35.00	30.4	29.3	20.1	36.9	36.5	35.9	36.4	36.8	37.8	37.7	36.4b	36.8
7	40.4	41.7	77.52	76.2	75.0	41.3	27.6	27.0	26.8	26.4	27.5	28.8	28.7	26.9	27.5
8	44.2	44.0	47.63	48.9	48.0	43.9	36.2	36.3	36.1	36.0	36.1	37.3	37.2	36.4b	36.3
9	56.1	56.2	47.89	47.4	48.6	55.8	40.0	38.7a	38.1	38.3a	39.9	39.9	39.9	38.4a	38.3
10	39.3	38.7	40.00	39.5	38.8	39.6	46.4	46.6	46.4	46.1	46.3	44.5	44.5	46.6	46.5
11	18.1	18.2	19.51	18.5	17.7	18.3	35.5	35.1b	35.5	35.0b	35.4	35.1	35.0	35.0	36.3
12	33.3	33.2	33.97	34.0	33.3	33.0	29.5	35.6b	35.4	35.8b	29.4	29.4	29.3	36.9a	35.0
13	44.2	44.2	44.41	44.3	43.4	43.9	30.9	31.0	30.6	30.6	31.0	30.9	31.1	164.4	164.6
14	39.9	39.7	39.10	39.1	38.4	38.5	41.6	41.7	36.5	41.0	41.5	41.6	41.5	114.9	114.8
15	49.2	49.1	47.41	46.6	45.6	48.8	179.4	179.8	62.8	172.8	173.8	179.4	173.8	172.0	172.1
16	156.0	155.9	155.24	156.2	155.4	155.4	19.9	19.9	19.6	19.5	19.9	19.8	19.8	19.5	19.5
17	102.8	103.0	104.09	103.6	103.2	103.1	16.0	16.1	15.7	15.5	15.9	16.0	15.9	15.9	16.0
18	33.7	27.1	30.08	28.6	28.5	22.8	19.9	18.4	18.3	18.0	19.9	33.0	33.0	18.3	20.0
19	21.7	65.6	184.05	178.2	179.0	64.3	18.0	20.0	19.3	19.5	18.0	20.1	19.9	20.0	18.0
20	17.6	18.1	15.93	15.7	15.4	18.3	18.5	18.1	17.8	17.8	18.4	17.4	17.3	17.9	18.3
C=O									178.6
MeCO									20.8
OMe										50.6	51.3		51.3
Carbon	Compound / δC (in ppm)
	34 [62]	35 [63]	36 [38]	37 [38]	38 [40]	39 [41]	40 [41]	41 [41]	42 [41]	43 [41]	44 [38]	45 [40]	46 [40]	47 [38]	48 [41]
1	18.37	18.40	17.5	18.6	18.1	29.4	16.2	18.2	27.3a	28.9	35.1a	35.6	35.6	35.6a	34.3a
2	26.98	26.92	27.1	24.1	27.7	125.6	30.3	27.4	65.6	69.5	199.1	201.2	200.2	200.0	200.5
3	120.52	120.46	120.0	123.3	120.3	171.0	76.2	120.4	122.1	124.4	128.5	125.5	125.5	125.5	127.4
4	144.60	144.50	143.7	139.8	144.4	168.7	76.5	144.5	150.1	147.9	168.6	173.4	171.0	172.6	172.6
5	38.28	38.30	38.0a	37.9	38.3	50.6	38.3	38.1	38.0	38.0	38.6c	40.0	38.8	39.9b	39.7
6	36.94	36.99	36.4	37.6a	36.1	34.4	32.4	36.8	36.4	36.5	36.8b	36.0	35.5	34.8a	35.5
7	27.61	27.63	26.4	28.9	26.8	28.3	26.4	26.8	27.2a	27.2	29.0	27.0	26.9	26.9	26.8
8	36.36	36.41	36.0	37.5	36.8	37.1	36.0	36.1	36.3	35.9	37.3	36.1	36.1	36.1	35.8
9	38.72	38.72	38.3a	38.9	38.1	37.5	41.2	38.3	38.9	38.6	39.3c	38.6	38.6	38.8b	38.3
10	46.53	46.60	46.0	44.9	46.3	53.9	40.7	46.3	40.4	45.2	45.7	45.7	45.7	45.6	45.5
11	36.63	36.72	34.2	35.0	31.8	33.5	32.2	31.8	31.0	31.8	35.4a	34.9	34.9	34.9a	31.1
12	32.95	32.97	37.7	37.0a	35.2	35.5	35.4	35.3	36.4	35.2	36.2b	36.0	34.7	35.9a	34.7a
13	140.93	143.22	160.8	164.5	73.3	73.0	73.5	73.4	73.2	73.3	30.7	30.8	30.4	30.9	73.0
14	123.13	118.03	114.5	115.1	145.2	144.9	145.0	145.1	146.4	145.0	41.4	41.5	36.9	41.3	144.8
15	59.51	61.44	166.5	172.4	111.6	111.9	111.6	111.8	110.9	111.9	178.7	178.9	63.0	173.4	111.9
16	16.52	16.70	18.5	19.6	27.4	27.8	27.4	27.7	26.3	27.7	19.9	19.9	19.9	19.8	27.7
17	16.07	15.98	15.5	16.1	15.8	15.0	15.9	15.9	15.8	15.9	16.0	15.7	15.8	15.7	15.6
18	18.45	17.92	18.0	20.0	18.3	11.7	21.3	18.0	17.9	17.7	20.5	18.4	18.5	18.4	18.9b
19	20.03	19.99	19.5	33.2	19.8	16.9	17.2	19.8	18.3	19.9	32.1	18.9	18.7	18.9	18.2b
20	18.07	18.34	17.8	17.9	17.8	18.2	18.5	18.4	18.3	18.5	18.0	17.9	18.0	18.0	17.9
C=O		170.94											178.9
MeCO		20.94											20.8
OMe			50.1											51.4
	Compound / δC (in ppm)
Carbon	49 [38]	50 [38]	51 [38]	54 [41]	56 [46]	57 [40]	58 [64]	60 [40]	61 [54]A	62 [55]	63 [65]	65 (?) [66]	66 [40]	67 [40]
1	35.4a	35.4a	35.6a	22.0	74.18	39.1	39.8	39.0	40.4	33.1	39.1	19.45	43.9	36.9
2	200.3	200.0	200.2	79.2	128.68	18.2	-	18.2	19.0	21.7	19.4	22.36	19.5	19.0
3	128.5	125.3	125.4	116.7	136.84	42.1	41.9	41.9	42.7	35.4	42.1	24.51	42.0	41.2
4	167.5	172.3	172.7	155.0	80.48	33.1	-	33.3	33.7	39.1	33.6	33.64	34.5	33.2
5	38.6b	39.8b	39.9b	37.8	37.16	55.9	56.1	55.8	56.9	36.6	55.5	55.59	57.5	51.8
6	36.7a	34.8a	34.9a	33.2	25.59	18.1	23.5	18.1	21.1	28.6	24.5	32.75	69.4	19.0
7	28.9	26.7	26.9	27.1	17.33	41.3	44.7	40.5	45.1	37.4	38.3	38.41	47.7	33.5
8	36.6	36.1	36.1	36.4	47.58	73.3	74.4	73.3	73.9	160.6	148.3	148.17	144.0	125.4
9	39.9b	38.7	38.7b	39.1	35.28	59.3	61.3	58.2	62.3	48.6	56.2	57.20	56.7	140.4
10	45.7	45.6	45.8	40.4	44.49	38.9	39.2	38.8	39.8	40.0	39.7	39.80	40.9	37.2
11	34.0	34.2a	34.0a	30.7	41.90	22.3	20.5	22.4	20.0	27.5	21.5	38.96	21.6	25.3
12	36.8a	35.9a	35.9a	36.1	70.66	42.1	44.5	41.9	46.2	29.8	40.1	42.21	39.5	41.7
13	160.3	162.6	160.3	73.9	124.79	30.9	163.9	30.9	73.3	30.8	164.3	160.69	160.7	31.1
14	115.2	115.1	115.3	146.3	108.40	40.5	114.7	144.7	147.5	41.4	114.6	115.73	115.2	145.9
15	167.0	171.2	167.1	111.2	139.66	177.9	171.5	111.8	110.7	179.8	171.8	166.40	167.3	112.0
16	19.1	19.3	19.1	25.0	143.96	19.5	19.4	19.5	27.8	19.8	19.2	14.51	19.0	20.0
17	15.9	15.5	15.7	15.6	175.48	30.5	24.0	30.4	24.5	102.5	106.4	21.73	110.3	19.4
18	20.5	18.2	18.4	18.3	172.37	21.5	21.5	21.5	33.7	18.2	33.6	25.26	23.6	21.5
19	32.1	18.7	18.9	18.1	27.00	33.3	33.4	33.1	21.8	20.8	21.7	33.64	33.7	33.2
20	17.8	17.6	17.9	18.4	24.31	-	15.4	-	15.8	15.9	14.5	106.53	17.1	19.3
1’			50.8
2’
3’	50.7											50.56	50.8

a, b, and c may be interchanged for the same structure; (*) reassigned 13C-NMR data in CDCl3; (P) 13C-NMR data in C5D5N; (D) 13C-NMR data in DMSO-d6; (A) 13C-NMR data in acetone-d6; (?) solvent not given

Table 5

13C-NMR data (in CDCl3) of substituted diterpenes isolated from Aristolochia species.

Carbon	Compound / δC (in ppm)			Carbon	Compound / δC (in ppm)
	24 [ 31]	25 [ 31]	26 [ 31]		24	25	26
1	40.3	40.4	40.4	1’	-	-	-
2	18.6	-	-	2’	112.7	112.8	112.5
3	41.9	42.0	42.0	3’	143.1	-	-
4	33.3	-	-	4’	147.5	146.8	146.2
5	56.0	56.1	56.2	4a’	-	-	-
6	20.5	-	20.5	4b’	131.0	-	131.0
7	42.1	42.0	42.0	5’	119.2	127.4	119.2
8	44.9	-	-	6’	131.0	130.5	-
9	56.7	56.6	56.5	7’	108.0	-	108.0
10	39.4	-	-	8’	156.9	130.2	156.9
11	18.3	-	-	8a’	120.2	128.5	120.2
12	26.3	27.1	27.4	9’	121.2	126.5	121.1
13	46.3	46.5	43.5	10’	145.9	-	-
14	37.2	37.5	38.1	10a’	-	118.3	119.2
15	53.3	53.4	51.0	11’	167.2	167.5	167.2
16	80.1	80.0	-	OCH2O	102.4	103.0	102.4
17	69.6	70.2	63.7	OMe	56.2		56.2
18	33.6	33.6	33.6
19	21.5	22.0	21.6
20	17.8	18.0	17.8

(-) Data not observed

Kaurane derivates isolated from Aristolochia species

Kaurane diterpenoids show several biological properties such as antioxidative, antityrosinase [27], abortifacient, and anti-inflammatory activities, they are used against snake bite poisoning [28], and present cytotoxicity against tumor cells of human prostate, colon, and breast cancer [29]. Table 1 lists the kaurane derivates isolated from Aristolochia species (1 to 26 in Figure 2 and Figure 3) and their respective plant sources. Acetonide 13 and kaurane derivative 14 were isolated from A. rodriguesii and A. triangularis, respectively. Both compounds were also prepared from 3 [30].

Clerodane derivatives isolated from Aristolochia species

Clerodane diterpenoids show a broad spectrum of biological properties [35,36] including insecticidal activity [37]. Table 2 shows the clerodane diterpenoids isolated from the genus Aristolochia (27 to 55 in Figure 4 and Figure 5) and their respective plant sources. Structure 52 has been also named as 2-oxokolavenic acid (50). The corresponding acid of 49 has been described by Wu et al. [16].

Analgesic and anti-inflammatory activities have been observed for furanoditerpenes [42,43], and their derivatives also show sedative [42], anticonvulsant [44], and plant growth regulatory activities [45]. Columbin (56) was isolated from A. albida [46] (Figure 6). The furan moiety is not fused to other rings, as is commonly found in several furanoditerpenes from natural products or synthesized [47]. It is the only furanoditerpene found in the genus Aristolochia.

Labdane derivatives isolated from Aristolochia species

Labdane diterpenoids are fungal growth regulator and plant growth inhibitor [48,49,50], showing high antibacterial activity [51]. Commercially, labdanes are used as natural fixatives, modifiers, and lotions by the perfume industry, and as a flavouring agent in the tobacco industry [52]. Table 3 shows the labdane diterpenoids isolated from Aristolochia species (57 to 67 in Figure 7). Structures 58 and 59 have both been named as ent-labd-13-en-8β-ol-15-oic acid [53].

13C-NMR data of diterpenes

Table 4 and Table 5 show the 13C-NMR data of the diterpenoids 1 to 67. In Table 4 the 13C-NMR data of 17 (in CDCl3) were reassigned and a new structure 22 was proposed according to 13C-NMR data in CDCl3, C5D5N, and DMSO-d6 [34] (see Figure 2). The carbon chemical shifts of the kaurane diterpenoids 1 to 23 are characteristic only at region between δC 38.0 and 42.0 assigned to C-1 and C-10. The other carbon chemical shifts do not show any characteristic features for this skeleton type. In diterpenes 15 and 16 containing a double bond between C-15 and C-16, the carbon chemical shifts are registered near δC 135.0 and 145.0, respectively. On the other hand, the double bond is located between C-16 and C-17 of 17 to 23 and their carbon chemical shifts are registered near δC 156.0 and 103.0, respectively.

The characteristic carbon chemical shifts for clerodane derivatives (except for 39 and 40) are observed around δC 120.0-123.0 and 139.0-145.0, which are assigned to C-3 and C-4, respectively, as shown in Table 4 (see Figure 4 and Figure 5). However, the carbon chemical shift ranges show higher values when C-2 is oxygened, as is the case of 42 to 55 (Figure 5). The carbon chemical shifts around δC 38.0-40.0 (assigned to C-5 and C-9) and δC 36.0-38.0 (assigned to C-6 and C-8) are registered in the 13C- NMR spectra of these compounds. Values close to δC 145.0 and 112.0 are assigned to the double bond between C-14 and C-15 in clerodane diterpenoids, as shown in 38-43, 48, and 54. Besides, the values close to δC 160.0 and 115.0 were assigned to double bond between C-13 and C-14, respectively, and δC 73.0 for hydroxylated C-13 of these compounds.

Structure of furanoditerpenes (Figure 6) can be confirmed by carbon chemical shifts at δC 124.79, 108.40, 139.66, and 143.96 assigned to C-13, C-14, C-15, and C-16, respectively for 56.

Despite the fact that 61 was not isolated from an Aristolochia species, its stereochemistry is close to that of 59 (see Figure 7). Thus, 13C-NMR data of 61 were included in Table 4 to provide insights about the corresponding data of 59. The carbon chemical shifts close to δC 145.0 and 112.0 are assigned to double bond between C-14 and C-15 in labdanes, as shown in Table 4 for 60, 61, and 67. Values close to δC 160.0 and 115.0 can be assigned to double bond between C-13 and C-14 in 58 and 63-66.

Table 5 shows the 13C-NMR data of the substituted kaurane diterpenoids 24 to 26 (see Figure 3). These compounds present an aristolochic acid derivative bound to a kaurane diterpenoids at O-16 (for 24 and 25) and O-17 (for 26). Some carbon chemical shifts were not observed in the 13C NMR data of 25 and 26. As it would be expected only the carbon chemical shifts of C-13 to C-17 of 26 are different when comparing to 24 and 25.