What Active Ingredient in Valerian Essential Oil?

Valerian (Valeriana officinalis L.) belongs to the Valerianaceae family, is a perennial herbaceous plant, with approximately 250 species worldwide. It thrives in mild, humid regions and is widely distributed across Europe, Asia, and South America. China has around 30 species, primarily distributed in the northeastern and southwestern-northwestern regions. Valerian contains a rich array of chemical components, including essential oils, lignans, alkaloids, and triterpenoids, most of which are distributed in the plant's nutritional organs and exhibit significant pharmacological effects.

In recent years, the remarkable pharmacological properties of valerian have attracted extensive research from scientists, with a particular focus on its physiological activities. In recent years, research on the pharmacological mechanisms of Valeriana has been relatively in-depth, with a particular focus on the nervous system and antitumor effects. Over the past 20 years, studies have revealed that the pharmacological effects of Valeriana primarily include sedation and sleep promotion, anxiolysis, antitumor activity, and antispasmodic effects. Experimental evidence has demonstrated that Valeriana is non-toxic and has no adverse side effects, making it highly safe. This paper primarily discusses the chemical composition and pharmacological effects of Valeriana officinalis essential oil, aiming to provide a reference for further research on Valeriana officinalis.

1 Chemical Composition of Valeriana officinalis Essential Oil

The content of Valerian volatile oil typically ranges from 0.5% to 2%. Ain Raal et al. [1] measured volatile oil content in five root samples, ranging from 0.28% to 1.16%. The main components of volatile oil in Valerian are primarily divided into monoterpenes and sesquiterpenes. Monoterpenes primarily include borneol and its isopentanoate and acetate esters; sesquiterpenes are relatively low in content but diverse, exceeding 30 types, mainly comprising Valerian-type sesquiterpenes and guaiazulene-type sesquiterpenes [2].

Other components include camphene, α-pinene, 1-limonene, phellandrene, borneol, d-terpineol, and α-fenchene, among others. Due to factors such as variety, harvesting time, and place of origin, the components and content of volatile oils may vary. For example, the content of volatile oils in valerian decreases with storage time; the content is lower in one-year-old valerian compared to multi-year-old valerian; Valerian grown in fertile sandy soil has higher volatile oil content than that grown in other soil conditions, and Valerian cultivated from September to November has higher volatile oil content. Abdollah et al. [3] compared the essential oils of the aboveground and underground parts of Iranian Valerian and found that the essential oil content of the underground parts was significantly higher than that of the aboveground parts. Additionally, components such as valerenic acid present in the essential oil of European valerian are absent in the essential oil of domestic Valeriana species, which may be the primary distinction between the two.

2 Chemical composition of Valeriana essential oil

Wu Zhuping et al. used GC-MS for identification. Through the analysis of the components of European valerian essential oil, a total of 36 compounds were identified, including 19 terpenes, 7 alcohols, 2 ketones, 6 esters, and 2 acids. Among these, the content of borneol acetate was the highest [4]. In the genus Valeriana, the content of borneol acetate in the essential oils of Valeriana officinalis, Valeriana pilosa, and Valeriana latifolia exceeds 30%, with some Valeriana latifolia samples reaching as high as 60%.

Experimental determination of the volatile oil of Spider Fragrance revealed that borneol acetate is an important component of Spider Fragrance, but it accounts for only 4% to 10% of the total. Additionally, three new sesquiterpenoid compounds were isolated, and analysis identified 76 components and six new unknown compounds. Douxiao Wei et al. [5] used GC-MS to determine the chemical composition of black water valerian essential oil, identifying four new compounds with sedative effects: valerianone, linalool, isovaleric acid borneol ester, and limonene. Fan Hao et al. [6] first isolated 8-acetoxylpathchouli alcohol, myristic acid, and lauric acid from Valeriana, and also isolated three compounds—n-hexacos-5,8,11-trienoic acid, 4-epipenlanbutenolide, and xylariamide—for the first time in the Valeriana genus.

3  Effects of different factors on the content of volatile oils in Valeriana

3. 1  Seedling grading

Nie Xianyü, Lu Chunyun, et al. analyzed the seedling characteristics and agronomic traits of broad-leaved Valeriana and established quality grading standards for Valeriana seedlings. They found that seedling grading significantly affects the yield, germination rate, and volatile oil extraction rate, with Grade I seedlings > Grade II seedlings > Grade III seedlings, and the volatile oil extraction rates of Grade I and Grade II seedlings being significantly higher than those of Grade III seedlings [7].

3.2 Cultivation Measures

Cultivation density has a certain influence on the accumulation of active components in valerian. By setting different cultivation densities, it was found that high density is not suitable for the growth and development of valerian plants or the accumulation of active components. Research has shown that the optimal planting density for Valeriana is 25–30 cm between plants and 40–50 cm between rows. Low moisture content is unfavorable for the accumulation of volatile oil in broad-leaved Valeriana, while adequate moisture content is beneficial for root growth and volatile oil accumulation.

3.3 Planting Site

Broad-leaved valerian is suitable for cultivation in cool, moist environments with high cold tolerance. The optimal altitude is 1,000–1,200 meters, and a large diurnal temperature range is beneficial for the accumulation of underground rhizomes and root substances, thereby increasing oil content. Research has shown that the fingerprint spectra of volatile oils from broad-leaved valerian grown at different altitudes are largely identical, with the content of acetyl camphor ester increasing in direct proportion to altitude.

3.4 Harvesting time

Harvesting valerian too early results in insufficient essential oil content, while harvesting too late causes the essential oil to evaporate easily. The optimal harvesting time is late July to early August, when the leaves turn yellow and the roots become yellowish-black. Research data indicates that valerian harvested in the autumn following winter sowing yields the highest production and oil content. In perennial valerian, the fibrous roots of the first year are mostly withered and dead, leading to reduced yields.

3.5 Extraction Methods

Water steam distillation is cost-effective and requires simple equipment, but has low extraction efficiency. Supercritical CO₂ extraction operates at low temperatures, achieves high extraction efficiency, and does not affect the bioactivity of valerian's heat-sensitive compounds, resulting in essential oil with a fragrance close to natural. However, it is costly and currently mainly used in laboratory research. Additionally, other methods such as solvent extraction and cold pressing exist, but their adaptability and feasibility are lower compared to steam distillation.

4 Pharmacological Effects of Valerian Essential Oil

4.1 Effects on the Central Nervous System

Jin Chang et al. [8] administered different doses of Valerian essential oil to mice via oral gavage, observed the effects on the mice's spontaneous activity and the effects on sleep under the synergistic action of pentobarbital sodium. The results showed that volatile oils at all doses significantly reduced the number of mouse activities and increased the sleep index, with higher doses showing a more pronounced effect than lower doses. This indicates that North Valerian volatile oil has sedative effects. A study involving 85 patients who underwent anal and rectal surgery was conducted, comparing the effects of essential oil acupoint massage intervention with a standard care control group. The results showed that patients receiving essential oil acupoint massage intervention had significantly longer sleep duration and fewer awakenings compared to the control group. Filip Bellon et al. [9] also confirmed in a study on the effects of nursing intervention on sleep in hospitalized patients that essential oil acupoint massage can significantly improve sleep quality. Additionally, valerian essential oil promotes sleep onset efficiency in mice, prolongs sleep duration, and exhibits significantly superior effects compared to its water extract.

4.2 Anticonvulsant, Antidepressant, and Antiepileptic Effects

A study investigating the effects of black valerian essential oil on thioamide-induced seizures in mice demonstrated that black valerian essential oil possesses significant anticonvulsant effects. The forced swimming test in mice confirmed the antidepressant effects of valerian essential oil, with the mechanism of action potentially involving the regulation of the nitric oxide signaling pathway by terpenoids present in the essential oil. Zhao Lihui et al. [10] analyzed the active components of the water extract obtained by distillation of Valeriana officinalis, and detected the antidepressant active components through in vivo experiments in mice. The experimental results indicated that the water extract of Valeriana officinalis possesses antidepressant activity. Forced swimming experiments in mice demonstrated that both the ethanol extract and water extract of Valeriana officinalis shortened the depressive state in mice, exhibiting antidepressant effects without central nervous system excitatory effects, and could serve as a new source for antidepressant drugs. Through anti-depressant activity tracking and screening, two compounds with anti-depressant activity were identified in Valeriana officinalis essential oil: kessanol, a creosote-type sesquiterpene, and cyckokessyl acetate.

Some researchers observed changes in GABA and Glu levels in the brains of epileptic mice treated with Valerian volatile oil compared to a control group and found that Valerian can regulate the balance of excitatory and inhibitory amino acids in the brains of epileptic mice. Therefore, Valerian volatile oil may have antiepileptic effects.

4.3 Applications in Agriculture

Bornyl acetate and camphene are the main components of Valeriana volatile oil. Studies have shown that the binary mixture of camphene and bornyl acetate from Valeriana plants exhibits contact and repellent effects against three storage pests, confirming that Valeriana can serve as a source of plant-based insecticides. Hu Huanfu et al. [11] used Valerian essential oil as a preservative and sprayed it on summer black grapes stored at room temperature. The experimental results showed that Valerian essential oil has the effects of inhibiting respiration, improving fruit quality, and extending the shelf life of fruits, making it a natural preservative and has significant value in the storage and preservation of fruits and vegetables.

4.4 Antimicrobial and Antioxidant Effects

Zhao Bing et al. [12] conducted antibacterial and antioxidant studies on Valeriana officinalis and Spider Lily essential oils. Using methods such as disk diffusion to measure the size of the inhibition zone and the minimum concentration, and the DPPH method to study their antioxidant capacity, the experimental results indicated that both essential oils possess certain antibacterial and antioxidant capabilities, with Valeriana officinalis essential oil exhibiting weaker antibacterial activity than Spider Lily essential oil. Experiments demonstrated that Valerian essential oil exhibited significant inhibitory effects against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli, with the inhibitory effects decreasing in the order of Bacillus subtilis, Staphylococcus aureus, and Escherichia coli.

4. 5 Prevention of Pulmonary Inflammatory Diseases

Chen Na et al. [13] induced acute lung injury in mice using lipopolysaccharide and pretreated them with borneol acetate 1 hour prior to induction. The results showed that borneol acetate downregulated the levels of pro-inflammatory cytokines in vivo and in vitro, reduced the total number of cells, neutrophils, and macrophages in BALF, attenuated histological changes in the lungs, reduced the wet-to-dry weight ratio of BALF; and inhibited the activation of NF-κB inhibitor α, extracellular signal-regulated protein kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase. These results suggest that acetyl borneol is a potential therapeutic agent for acute lung injury.

4. 6 Effects on the cardiovascular system

Li Ying et al. [14] investigated the effects of different doses of Valerian volatile oil on cerebral microcirculatory perfusion in mice. The results showed that the brain radiation counts and brain/blood ratios in all dose groups were higher than those in the control group. This experimental result demonstrates that Valerian volatile oil can improve cerebral blood supply in mice and increase cerebral tissue blood flow perfusion. Additionally, broad-leaved valerian essential oil can alleviate angina symptoms and recover myocardial ischemia, with its mechanism of action potentially involving coronary artery vasodilation and reduced myocardial oxygen consumption.

4.7 Other effects

Studies have shown that valerian oil exerts renal protective effects through lipid regulation, downregulation of rGF-p expression, and inhibition of phenotypic transformation of glomerular mesangial cells and renal tubular epithelial cells. Some researchers observed mice with Alzheimer's disease using a water maze experiment and compared the mice before and after treatment with black valerian extract. They found that the mice's learning, memory, and spatial exploration abilities were significantly improved after intervention, indicating that black valerian extract has cognitive-enhancing functions [15].

5 Future Prospects

Valerian has a long history of use, with the earliest recorded mention in Li Shizhen's *Compendium of Materia Medica* during the Ming Dynasty. Ancient Greeks and Romans recognized its sedative and calming effects. In 1983, valerian was included in the European Pharmacopoeia as a sedative, and later added to the pharmacopoeias of the United States, Germany, and the United Kingdom. Since its discovery, Valerian has been highly valued for its medicinal properties, with virtually no side effects. Its preparations are in high demand internationally, with sales ranking among the top 10 plant-based medicines.

In China, GB 2760-2014, the “National Food Safety Standard for the Use of Food Additives,” permits the addition of valerian essential oil and valerian root extract as natural flavorings in food. Currently, spider incense has been included in the Chinese Pharmacopoeia, but valerian has not yet been listed in the “Chinese Pharmacopoeia.” Research on Valerian volatile oil in China is limited, and it remains in the clinical application and research stages. China's development of Valerian is relatively lagging behind. With increasing life pressures, more people are prone to anxiety and insomnia, which not only affect work performance but also pose significant health risks. The growing number of patients has led to a continuous rise in demand for anti-insomnia medications. As a natural medicine with high safety and minimal side effects, Valerian holds great market potential.

References

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