Chemical Components and Cardiovascular Activities of Valeriana spp.

Valeriana spp. is a flowering plant that is well known for its essential oils, iridoid compounds such as monoterpenes and sesquiterpenes, flavonoids, alkaloids, amino acids, and lignanoids. Valeriana spp. exhibits a wide range of biological activities such as lowering blood pressure and heart rate, antimyocardial ischemia reperfusion injury, antiarrhythmia, and regulation of blood lipid levels. This review focuses on the chemical constituents and cardiovascular activities of Valeriana spp.

1. Introduction

Valeriana officinalis Linn, perennial herbaceous plant belonging to the Valerianaceae family, is widely distributed in temperate regions. It comprises approximately 250 species, and 11 out of the 28 (including 1 variant) Chinese varieties are used as herbal medicines [1-4]. Most research studies have focused on six species: V. officinalis L., V. jatamansi Jones, V. officinalis L. var. latifolia Miq., V. amurensis Smir. ex Kom., V. fauriei Briq., and V. alternifolia var. stolonifera Bar. et Skv.

The roots and rhizomes of Valeriana spp. are rich in essential oils, iridoids, flavonoids, alkaloids, amino acids, and lignanoids [5-9], which possess characteristic fragrance or off-flavor and are used as medicines based on their inherent bioactivities that include inducing sedation, promoting sleep, antidepression, and antianxiety [10-18]. Valeriana spp. is now listed in the European and USA pharmacopeias. It is also sold as a diet supplement in the USA and is one of the highest selling natural medicines in Europe and the USA [19]. In addition, Valeriana spp. is of high medical and economic value in the food, drink, and cosmetic industries due to its distinct flavor, and current research efforts are aimed at further exploiting other features of the plant [20, 21]. This review focuses on the chemical constituents and cardiovascular activities of Valeriana spp., aiming at providing a theoretical foundation for further research and evaluation of its medicinal value.

2. Chemical Constituents

2.1. Essential Oils

Approximately 0.5%–2.0% of Valeriana spp. consists of essential oils by gas chromatography-mass spectrometry (GC-MS), which varies with species, climate, and growing environment. Valerian plants from high-altitude fertile and sandy soil have significantly higher essential oil content and yield similar to that of biennials compared to annuals. Valerian plants that produce a higher amount of essential oil are cultivated between September and November, although the content of essential oils decreases with longer periods of propagation.

A total of 150 compounds have been identified in the essential oils of Valerian plants, mainly including monoterpenes and sesquiterpenes. Most monoterpenes, namely, borneol, bornyl acetate, and isobornyl acetate, exhibit various bioactivities. Around 30 sesquiterpenes have also been detected in the Valerian essential oils. These have been classified to be of the guaiane type and valerian type. Despite the low contents of these essential oils, their biological activities have drawn the attention of researchers around the world [22-24].

Long et al. [25], Ming et al. [26], Wang et al. [27], and Yu et al. [28] previously investigated essential oils from Valeriana by GC-MS, showing its content was 1%, and 20%–60% of it was bornyl acetate. Wang et al. [27] detected 34 compounds by GC-MS, which comprised 91.75% of the total content of the essential oil of V. officinalis L. var. latifolia Miq. (Table 1 and Figure 1). Compared to the standard spectrum, bornyl acetate showed the highest content level at 23.93%, followed by nootkatone (14.79%) and 6-isopropyl-1-methyl bicycles [3,1,0] hexane (14.19%).

Table 1

The list of essential oil constituents from V. officinalis L. var. latifolia Miq.

Signal	Compounds	Molecular format	Molecular weight	Retention time (min)	Content (%)
1	Carene	C10H16	136	6.100	0.29
2	α-Thujene	C10H16	136	6.473	4.18
3	6-Isopropyl-1-methyl bicycles [3,1,0] hexane	C10H16	136	6.983	14.19
4	Sabinene	C10H16	136	7.736	2.55
5	p-Cymene	C10H14	134	9. 143	0.43
6	Limonene	C10H16	136	9.281	1.26
7	Camphor	C10H16O	152	12.596	0.19
8	Borneol	C10H18O	154	13.671	3.54
9	L-Myrtanol	C11H16O	164	14.584	0.81
10	α-Methyl 4(1′, 1′-methyl ethyl) phenol	C11H16O	164	15.432	2.49
11	Bornyl acetate	C12H20O2	196	17.311	23.93
12	Sabinol	C10H16O	152	18.270	1.70
13	α-Terpineol	C10H18O	154	18.944	1.20
14	β-Caryophyllene	C15H24	204	20.989	0.82
15	β-Gurjunene	C15H24	204	21.343	1.16
16	Humulene	C15H24	204	21.891	0.40
17	Unidentified	C15H22	202	22.045	1.32
18	trans-caryophyllene	C15H24	204	22.450	0.28
19	Nerolidol	C15H24O	220	22.838	0.78
20	Elemene	C15H24	204	22.977	0.45
21	Bornyl isovalerianate	C15H26O	238	23.441	0.36
22	Azulene furan	C15H10O2	222	23.867	0.58
23	Stereoisomer of ramie enol	C10H16O	152	24.485	1.46
24	4a,8-Dimethyl-α-isopropyl naphthyl ketone	C15H24O	220	25.155	2.77
25	Tetramethyl-4-hydroxyl cyclopropane naphthalene	C15H24O	220	25.294	1.26
26	Unidentified	C15H24O	220	25.790	1.72
27	Ledol	C15H26O	222	27.011	1.22
28	Guaiol	C15H26O	222	27.150	4.73
29	Valerone	C15H26O	222	27.493	1.14
30	Nootkatone	C15H22O	218	29.031	14.79
31	Nootkatone isomer 1	C15H22O	218	29.467	1.06
32	Nootkatone isomer 2	C15H22O	218	30.333	0.90
33	1,2,3,4,4a,5,6,8,8a-Eight hydrogen-4a,8-dimethyl-α-Propenyl [α] naphthyl alcohol	C15H24O	220	35.174	0.83
34	Unidentified			36.500	0.83

Figure 1

Major essential oil constituents from V. officinalis L. var. latifolia Miq.

Yu et al. [28] analyzed essential oils from cultivated V. officinalis L. var. latifolia Miq. by GC-MS and identified 6 compounds, bornyl acetate (60.19%), (−)-acetic acid Rhodomyrtus enol ester (3.87%), α-terpinyl acetate (1.55%), acetyl carene (1.68%), α-selinene (26.07%), and (Z,E)-α-farnesene (1.56%), comprising 94.92% of the total content. Cultivated V. officinalis L. var. latifolia Miq. consisted of a higher number of simple components, which was predominated by bornyl acetate relative to that of wild V. officinalis L.

2.2. Iridoids

Valepotriate was first isolated from V. wallichii and preliminary studies by Thies and Funke [29] have confirmed the presence of a sedation ingredient. The study drew the attention of researchers from around the world. To date, over 130 iridoids from Valeriana spp. have been identified, possibly contributing their sedative, antidepressant, and antitumor activities.

Chen et al. [30] studied the levels of valepotriate, dihydrovalepotriate, and acetyl-valepotriate from V. jatamansi Jones, V. officinalis L., and V. officinalis L. var. latifolia Miq. by using the reverse phase high-performance liquid chromatography (RP-HPLC) method. The highest levels were observed in V. jatamansi Jones, followed by V. officinalis L. and V. officinalis L. var. latifolia Miq. In addition, the content of iridoid varied significantly among different parts and habitats.

The main iridoids in Valeriana comprised didrovaltrate and valepotriates derivatives (0.5%–9.0%), including valepotriate, isovalepotriate, acetoxyvalepotriate, and isovalemxy-hydroxy-dihydrovatrate. These were characterized by a hemiacetal fragment, which leads to the decomposed productions of isopentoic acid and valerienal at a specific pH or 60°C. C-1, C-7, C-10, or C-11 of compounds were mainly substituted by acyl groups such as acetyl, isovaleryl, α-acetoxyisovaleryl, β-acetoxyisovaleryl, and β-hydroxyisovaleryl. Furthermore, iridoids could be further divided into diethenoid-type, monoethenoid-type, and other types based on the parent structure.

2.2.1. Diethenoid-Type Iridoids

Diethenoid-type iridoids were characterized by the following molecular structures: (1) two C-C double bonds often presented between C-3 and C-4, C-5, and C-6 and occasionally presented between C-4 and C-5, C-6, and C-7; (2) an oxacyclopropane was often presented between C-8 and C-10, and C-10 was usually in a β-configuration; (3) H-1 (α-configuration) and H-9 (β-configuration) were preferentially located on different sides of the ring, and the C-7 acyl group usually was determined to be in the β-configuration (Figure 2 and Table 2 and Figure 3 and Table 3).

Figure 2

Compounds of diethenoid epoxy-type iridoids from Valeriana spp. (see Table 2).

Table 2

Number	R1	R7	R11	Compounds	References
1-1	a	a	b	Valtrate	[6]
1-2	a	f	b	Acevaltrate	[6]
1-3	a	b	a	Isovaltrate	[35]
1-4	a	H	b	7-Epi-deacetylisovaltrate	[36]
1-5	a	H	a	Deacetylisovaltrate	[37]
1-6	d	a	b	Homovaltrate 1	[35]
1-7	a	b	d	Homovaltrate 2	[35]
1-8	f	a	b	1-β-Acevaltratum	[38]
1-9	g	a	b	1-Seneciovaltrate	[39]
1-10	a	b	b	Diavaltrate	[40]
1-11	f	f	b	1-β-Aceacevaltrate	[40]
1-12	c	b	a	Homoisovaltrate	[41]
1-13	c	c	b	1,7-Dihomovaltrate	[41]
1-14	e	a	b	1-α-Acevaltrate	[41]
1-15	e	c	b	Homo-A	[41]
1-16	c	b	b	Homo-B	[41]
1-17	a	c	k	Homo-Z	[41]
1-18	e	b	a	1-α-Aceisovaltrate	[42]
1-19	a	c	b	Homovaltrate	[43]
1-20	c	f	b	1-Homovaltrate	[44]
1-21	c	b	e	1-Homoisoacevaltrate	[44]
1-22	g	a	a	Sorbifolivaltrate A	[45]
1-23	g	c	b	Sorbifolivaltrate B	[45]
1-24	a	a	H	Deacetlyvaltrate	[46]
1-25	a	c	b	7-Homovaltrate	[46]
1-26	c	a	b	1-Homovaltrate	[46]
1-27	a	b	e	11-Acevaltrate	[46]
1-28	a	i	b	Homoacevaltrate	[46]
1-29	a	k	b	Hydroxyvaltrate	[47]
1-30	a	h	b	Isohomovaltrate	[47]

Figure 3

Compounds of diethenoid open ring-type iridoids from Valeriana spp. (see Table 3).

Table 3

Number	R1	R7	R10	R11	Compounds	References
2-1	a	a	a	b	Valtrate-isovaleroxyhydrin	[37]
2-2	a	a	a	b	Valtrate hydrin B1	[47]
2-3	a	a	b	b	Valtrate hydrin B2	[47]
2-4	j	a	a	b	Valtrate hydrin B3	[47]
2-5	a	b	a	a	Valtrate hydrin B4	[39]
2-6	a	a	c	b	Valtrate hydrin B5	[39]
2-7	a	b	c	b	Valtrate hydrin B6	[39]
2-8	g	a	a	b	Valtrate hydrin B7	[39]
2-9	e	a	a	b	Valtrate hydrin B8	[39]
2-10	e	b	b	a	Acetoxydesiovaleroxy-1-α-acetoxy-isovaleroxy isovaltratehydrine	[42]
2-11	c	a	b	b	10-Acetoxy-1-homovaltrate hydrin	[44]
2-12	f	a	b	b	10-Acetoxy-1-acevaltrate hydrin	[44]
2-13	k	a	a	a	Sorbifolivaltrate C	[45]
2-14	g	c	a	b	Sorbifolivaltrate D	[45]
2-15	a	e	l	b	Valeriandoid F	[48]
2-16	a	b	X	a	Jatamanvaltrate I	[49]
2-17	a	H	a	b	Jatamanvaltrate J	[49]
2-18	a	a	H	a	Jatamanvaltrate K	[49]
2-19	a	a	b	b	10-Acetoxyvaltrahedrin	[49]
2-20	a	b	Cl	a	Rupesin B	[50]
2-21	b	H	Cl	a	Valeriandoids A	[51]
2-22	a	f	Cl	b	Valeriandoids B	[51]
2-23	a	b	a	a	Isovaltrate isovaleroyloxyhydrin	[51]
2-24	a	a	Me	b	Valeriandoids F	[52]
2-25	a	a	—	b	Volechlorine	[36]
2-26	a	—	—	a	Nardostachin	[53]
2-27	a	—	—	b	Jatamanvaltrate N	[50]
2-28	a	—	l	b	Jatamanvaltrate O	[50]
2-29	a	—	l	b	Valeriandoids D	[52]
2-30	—	—	l	b	Valeriandoids E	[52]
2-31	a	b	—	a	8,11-Desoidodidrovaltrate	[37]
2-32	d	b	—	a	8,11-Desoidohomoddidrovaltrate	[37]

2.2.2. Monoethenoid-Type Iridoids

Monoethenoid-type iridoids were predominantly aglycones, which are characterized by the following structures: (1) a carbon double bond occurring mostly between C-3 and C-4; (2) H-1 (α-configuration), H-5 or 5-OH (β-configuration), H-7 (β-configuration), and H-9 (β-configuration); (3) a triatomic heterocyclic structure occurring between C-8 and C-10, and C-10 is usually a β-methylene, which is called monoene closed-loop iridoids. When C-8 and C-10 were not in ring formation, the structure is classified as a monoene open-loop iridoid (Figure 4 and Table 4).

Figure 4

Compounds of monoethenoid-type iridoids from Valeriana spp. (see Table 4).

Table 4

Number	R1	R5	R7	R10	R11	Compounds	References
3-1	a	H	a	—	b	Didrovaltrate	[6, 37, 53]
3-2	a	OH	b	—	l	Isovaleroxyhydroxydihydrovaltrate	[43]
3-3	a	H	b	—	a	Isodidrovaltrate	[54]
3-4	a	OH	b	—	e	AHD-valtrate	[40]
3-5	a	OH	b	—	c	11-Homohydroxyldihydrovaltrate	[44]
3-6	c	H	b	—	a	Homodidrovaltrate	[37]
3-7	a	OH	H	—	l	Jatamanvaltrate L	[49]
3-8	a	OH	b	—	Et	Jatamanvaltrate M	[49]
3-9	a	OH	b	—	a	5-Hydroxydidrovaltrate	[49]
3-10	a	OH	H	b	l	Valeriotriate B	[55]
3-11	a	OH	b	l	l	Valeriotertrate A	[56]
3-12	a	OH	b	f	l	Jatamanvaltrate A	[49]
3-13	a	OH	b	a	l	Jatamanvaltrate B	[49]
3-14	a	OH	b	b	l	Jatamanvaltrate C	[49]
3-15	a	OH	b	X	l	Jatamanvaltrate D	[49]
3-16	a	OH	b	Me	l	Jatamanvaltrate E	[49]
3-17	a	H	b	f	a	Jatamanvaltrate F	[49]
3-18	a	H	H	b	a	Jatamanvaltrate J	[49]
3-19	a	H	b	H	a	Jatamanvaltrate K	[49]
3-20	a	H	b	b	a	Didrovaltrate acetoxyhydrin	[49]
3-21	a	OH	b	Cl	l	Volvatrate B	[57]
3-22	a	OH	H	Cl	l	Jatamandoid A	[58]

2.2.3. Other Types of Iridoids

Iridoids from Valeriana spp. were mostly of the two above-mentioned types (Figure 5). In addition, other types were also identified: (1) most of one type having free hydroxyl groups and ester groups, with a lactone structure between C-1 and C-3 and a double bond between C-4 and C-1, (2) an oxygen bridge between C-3 and C-8, C-3 and C-10, or C-8 and C-11, (3) cleaved Ring-A of other types forming a free hydroxyl or aldehyde group between C-1 and C-3 (e.g., see Lin et al. [31]).

Figure 5

Compounds of other types of iridoids from Valeriana spp.

2.3. Lignanoids

Recent researches have indicated that lignanoids are 7,9-monoepoxy lignin and a glycoside or bisepoxy lignin. Britta Schumacher isolated eight lignanoids from Valeriana officinalis, namely, pinoresinol-4-O-D-glucoside, lignans 8′-hydro-xypinoresinol, 7,9′-monoepoxylignans massoniresinol-4′-O-beta-D-glucoside, berchemol-4′-O-D-glucoside, 8′-hydroxy-pinoresinol-4′-O-D-glucoside, and 8-hydroxypinoresinol-4′-O-D-glucoside [32]. Piccinelli et al. isolated two novel lignan glycosides from Valeriana prionophylla, including fraxireslnol-4′-O-D-glucopyranoside and prinse-piol-4-O-D-glucopy-ranoside [33].

2.4. Alkaloids

Alkaloids in Valeriana spp. included chatinine, nordelporphine, norphoebine, thaliperphine, nantenine, phenanthrene, phoebine, dehydroaphine, valerine, valeriane, and oxoaporphine, which occupy the low level of 1% [3, 34].

2.5. Flavonoids

Flavonoids in Valeriana spp. were mainly acacetin, apigenin, diosmetin, luteolin, quercetin, kaempferol, linarin, and luteolin [10, 33, 34], which occurred at low levels.

2.6. Amino Acids

Free amino acids in the water extracts of Valeriana spp. included γ-amino butyric acid (GABA), tyrosine, refined ammonia acid, glutamine, caffeic acid, chlorogenic acid, tannins, and sitosterol. GABA, a well-studied inhibitory neurotransmitter, is involved in lots of metabolic activities [59-62].

3. Research Advances on the Cardiovascular Activities of Valeriana

3.1. Reduction in Blood Pressure Level and Heart Rate

The increase of peripheral resistance in blood circulation was the common characteristic for primary hypertension, whose pathological mechanism was related to an increase of peripheral vascular tone and structural change of vessel walls. Additionally, structure and function disorders of vascular smooth muscle cells (VSMC) also contributed largely to this abnormal change. Therefore, improving the contract status of VSMC, expending the peripheral vessels, and inhibiting abnormal growth of VSMC preventing or alleviating vessel reconstruction at the same time were the keys to treating hypertension. Wang et al. [63] cultured aortic medial smooth muscle cells from a 6-month-old aborted fetus and examined the migration of cultured cells by Boyden Chamber. They found essential oil (VOL) could significantly inhibit the migration of human VSMC in a dose-dependent manner. Yang et al. [64] observed the effect of VOL and L-nitro arginine methyl ester (L-NAME) on the contraction of VSMC through the analogous experiment and investigated changes of 3H-thymidine (3H-TdR) and 3H-Leucine caused by angiotensin II (Ang II) and different concentrations of VSMC. VOL markedly inhibited the Ang II-stimulated contraction and growth of VSMC, which was not affected by L-NAME. In addition, VOL inhibited the incorporation of 3H-TdR and 3H-leucine. Zhou et al. [65] found that VOL could decrease the heart rate and blood pressure (priority to diastolic pressure) of rabbit and prolonged the duration of ST segment and T wave in a dose-dependent manner. VOL could decrease heart rate and blood pressure stimulated by adrenaline, which might be related to relaxing VSMC, enlarging vessel diameter, and decreasing blood resistance. VOL also observably inhibited contraction of VSMC stimulated by adrenaline, dilated coronary arteries, and decreased myocardial oxygen consumption. The vasorelaxant effects of the EtOH extract (1 mg·mL−1) and 8-hydroxypinoresinol (100 µm) from the roots of Valeriana prionophylla have been already shown [66]. Fields et al. [66] reported that VOL could dilate pulmonary vessels in felines via a nonselective GABA mechanism and inhibited contraction of isolated frog hearts stimulated by cardenolide. It has already been shown that hexanic extracts (HEVe) from V. edulis ssp. procera enriched in valepotriates present vasorelaxant properties by blocking calcium channels. HEVe induced a significant concentration-dependent and endothelium-independent relaxation on isolated rat aorta precontracted with noradrenaline (0.1 µm). HEVe, the most potent extract (0.15–50 µg/mL), induced relaxation in aortic rings precontracted with KCl (80 mm), with IC50 value of 34.61 µg/mL and E max value of 85.0% [67].

3.2. Antimyocardial Ischemia Reperfusion Injury

As early as the 1980s, Zhang et al. [68] reported that the ethanol extract of valerian could dilate the coronary artery and reduce myocardial oxygen consumption in anesthetized cats. Yang et al. [69] reported that its essential oil and iridoids enhance microcirculation perfusion of the heart and kidney. The valerian extract can prevent injuries to myocardial ischemia reperfusion model in the rabbit by decreasing the levels of xanthine oxidase (XOD), malondialdehyde (MDA), and tumor necrosis factor-α (TNF-α), thereby increasing the 6-keto-prostaglandin F1α/thromboxane B2 (6-keto-PGF1α/TXB2) ratio. Huang et al. [70] conducted a study to investigate myocardial protection mechanism of monoterpene oxide of valerian (VMO). Compared to the control group, VMO showed a maximum change rate of left ventricular pressure, with a maximal rate of the increase of the left ventricular pressure (+d ip/t max) and maximal rate of the decrease of the left ventricular pressure (−d ip/t max) by 25.1% and 25.3%, respectively. Adenosine triphosphate (ATP) and energy charge (E ) increased by 72.8% and 20.9%, respectively, whereas myocardial creatine kinase-myocardial band (CK-MB) decreased by 20.7%. These results demonstrated the analogical performance between VMO and ischemic preconditioning pretreatment on cardio protection, which indicated a mobilizing myocardial endogenesis protective mechanism and an exoteric ATP-sensitive potassium channel. Yang et al. [71] set up an isolated rat ischemia reperfusion (I/R) heart model using a Langendorff-perfusion system, observing the effects of VOL pretreatment on I/R injury and related biochemical factors and cytosolic free calcium. The results indicated that VOL pretreatment markedly prevented I/R injury, weakened vasospasm perfusion, sustained the heartbeat, and reduced ventricular arrhythmic events in a dose-dependent manner. Simultaneously, VOL significantly lowered lactate dehydrogenase (LDH), creatine phosphokinase (CK), and MDA levels. The activities of superoxide dismutase (SOD), adenosine triphosphatase (ATPase), and glutathione peroxidase (GSH-Px) were enhanced. VOL reduced intracellular calcium in a concentration-dependent manner. The mechanism of action for VOL's aforementioned activities potentially involved preventing the increase in concentration of free Ca2+ and decrease in lipid peroxidation.

3.3. Antiarrhythmia

Arrhythmia is a common disease that involves various pathological mechanisms. Although western medicines have considerable efficiency, the adverse reactions at different levels and the development of arrhythmia caused by the drug itself have been reported. Therefore, it is imperative to discover an antiarrhythmic drug that features efficiency, stability, and the absence of adverse effects; these properties are inherent to traditional Chinese medicine, which are also of scientific and societal significance.

Arrhythmia induced by aconitine might be caused by myocardium excitability, which opens Na+ channel of the cardiac muscle and promotes sodium currents, resulting in a ventricular and supraventricular ectopic rhythm and ventricular tachycardia. Ventricular fibrillation induced by chloroform could be related to the release of neurotransmitters or adrenaline secretion in the adrenal medulla, as well as stimulation of β receptors [72, 73].

Jia and Zhang [74] found that chloroform extract of ethanol extract (v3d) could effectively prevent atrial fibrillation in mice induced by acetylcholine-calcium chloride and ventricular fibrillation induced by chloroform. It also protected rats from ischemia arrhythmia induced by ligation of the left anterior descending coronary artery. In addition, it effectively prevents dog auricular and renal vessels contraction induced by high K+ levels. Therefore, v3d prevents arrhythmia in various animal species partly by inhibiting Ca2+ channel from opening, which was induced by high K+ level.

Huang [75] found valerian extract (monoterpene and sesquiterpene oxides from essential oils) could dose-dependently reduce the duration of an action potential and inhibit Na current (I Na), L-type calcium current (I Ca-L), and transient outward potassium current (I to). It interacts with inactivated I Na and I Ca-L, although various concentrations of v3d had no detectable effect on the delayed rectifier potassium current (I K) or inward rectifier potassium current (I KI) or direct interference with adenosine triphosphate sensitive potassium current (I KATP). The impacts of the valerian extract on these ion pathways might have contributed to its antiarrhythmia activity.

Wen et al. [76] reported the water, essential oil, and other fractions of valerian could protect a rat model from arrhythmia caused by aconitine or chloroform. Water extract at a dose of 50 and 25 g·kg−1 (calculated as raw herb) effectively decreased the occurrence of ventricular fibrillation, delayed the occurrence of arrhythmia, and decreased the mortality rate. The essential oil at a dose of 50 and 25 g·kg−1 (calculated as raw herb) effectively inhibited arrhythmia that was induced by chloroform; other fractions also demonstrated antiarrhythmia activities at different levels. Duan [77] found two active compounds from V. officinalis L., prinsepiol-4-O-β-D-glucoside and 8-hydroxy pinoresinol-4-O-β-D-glucoside; both showed antiarrhythmia activities. The former imparted an inhibitory effect on the Kv1.5 channel, which is the key mechanism for antiarrhythmia activity.

It was shown that didrovaltrate blocks L-type calcium current in a concentration-dependent manner and probably inhibited these currents in its inactive state. Didrovaltrate at concentrations of 30 μg/L and 100 μg/L significantly decreased peak I Ca-L (I Ca-Lmax) from 6.01 to 3.45 pA/pF and 2.16 pA/pF, respectively. Didrovaltrate shifted upwards the current-voltage curves of I Ca-L without changing their active, peak, and reverse potentials. Didrovaltrate affected the steady-state inactivation of I Ca-L. The half activation potential (V 1/2) was significantly shifted from −26 to −36 mV, with a significant change in the slope factor (k) (from 8.8 to 11.1) [78].

Liu et al. [79] studied antiarrhythmia effective substances in serum of V. officinalis L. The study showed that borneol and bornyl acetate from Valerian essential oils and another unidentified compound from ethyl acetate extract could be absorbed into the blood in its original form, which indicated that this unidentified compound might be the main substance that contributes to the antiarrhythmia activity of the ethyl acetate extract.

3.4. Regulation of Blood Lipid Levels

Reports on V. officinalis L. var. latifolia Miq. (VOL) and its constituents in lipid regulation are limited. Hu et al. [80] examined the effects of VOL on blood lipid metabolism in rabbits with hyperlipidemia. VOL imparts a remarkable antilipid peroxidation effect, reduces the levels of serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and MDA, and elevates the levels of high-density lipoprotein cholesterol (HDL-C) and SOD. The results prove that it is imperative to further investigate the underlying mechanisms in regulating lipid metabolism. Si et al. [81] also demonstrated VOL could reduce the serum levels of total cholesterol, low-density lipoprotein, urinary albumin, and serum creatinine. Light microscopy and immunohistochemical stain revealed that, in the same time of lowering serum lipid, mesangial matrix index was significantly reduced, accompanied by decreased expression of TGF-β 1 and type IV collagen.

4. Conclusions

Valeriana spp. possesses a wide range of bioactivities, which have been conferred by its complex and diverse active ingredients. Although the effects of Valeriana spp. mainly affected the cardiovascular system in Section 3, its mechanism of action needs to be further investigated.