Valeriana wallichii DC, a New Chemotype from Northwestern Himalaya

Journal of Essential Oil Research: JEOR, Nov/Dec 2005 by Mathela, Chandra S, Tiwari, Mamta, Sammal, Subhash S, Chanotiya, Chandan S

Abstract

The major constituents of the oils from roots and rhizomes of Valeriana wallichii DC were separated and characterized by GC, GC/MS and NMR (^sup 1^H- and ^sup 13^C-). The chemical compositions of the oils show two chemotypes within Valeriana wallichii. The type-I was characterized by presence of maaliol (64.3%), viridiflorol (7.2%) and sesquiterpene hydrocarbons (19.2%). The type-II contained patchouli alcohol (40.2%), viridiflorol (5.2%), 8-acetoxy-patchouli alcohol (4.5%) and sesquiterpene hydrocarbons (34.5%). Viridiflorol and 8-acetoxy-patchouli alcohol have been isolated from V. wallichii for the first time. Since the V. wallichii is being commercially used even today in Nepal and India as a substitute for V. officinalis, the sharp chemical differences among V. wallichii materials necessitates their identification before commercial exploitation for phytomedicines and flavor chemicals.

Key Word Index

Valeriana wallichii, Valerianaceae, chemotypes, essential oil composition, maaliol, viridiflorol, patchouli alcohol, 8-acetoxy-patchouli alcohol.

Introduction

Valeriana wallichii DC, Indian Valerian, has been an ingredient of herbal medicines in Indian systems of medicine and is used as a substitute of European Valeriana officinalis in India. Survey and collection of V. wallichii DC from the northwestern Himalayan region showed morphologically similar but chemically distinct (chemotypic) essential oil compositions. Valeriana wallichii (Indian Valerian) grows in the northwestern Himalaya and has long been used in Ayurveda (Charak Samhita and Susruta) and Unani systems of medicine (1,2), which describes its use in the treatment of obesity, skin disease, insanity, epilepsy and snake poisoning. The crude drugs from the roots/rhizomes and Valerian derived phytomedicines are used as mild sedatives in pharmaceutical industiy. The roots/rhizome parts are highly aromatic and as a result Valerian oil is in great demand.

The pharmacological activity of Valerian is believed to be due to two major groups of constituents-the valepotriates and sesquiterpenoids. According to the European Pharmacopoeia, the crude drug Valerianae radix must contain not less than 0.5% (v/w) of essential oil. Earlier reports on V. wallichii root oil indicate wide variations in their chemical compositions and the major terpenoids reported include sesquiterpene hydrocarbons (ar-curcumene, β-farnesene, α- and β-patchoulenes and sesquifenchene), valeranone, cryptomeridiol, maaliol, xanthorrhizzol, patchouli alcohol, etc. (3-7).

As part of work on Himalayan Valenana species we have reported the chemical composition of the essential oils from the leaves and roots of V. wallichii (5) and had earlier observed compositional variations (4). We now report herein the existence of two chemically distinct species within V. wallichii (chemotypes) with no mixed populations.

Experimental

Plant material: Valeriana wallichii (roots/rhizomes) were collected from various natural habitats in Nainital, Pithoragarh, Almora, Chamoli, Rudraprayag districts of northwestern Himalayan region situated at different micro-climatic regions of Uttaranchal at three different stages of growth from March to October. The materials were also collected from different locations of Nepal (Baitadi and Bhaishyag). Plant materials were identified from Botanical Survey of India, Dehradun. Voucher specimens (No.Chem/DST/V.01-06-10) were deposited in the phytochemistry lab of chemistry department, Kumaun University.

Isolation of oil: Various collections of fresh roots of 2 kg each were steam distilled using copper still fitted with spiral glass condensers for 2 h obtaining 5 L water distillate. The distillate saturated with NaCl was extracted with hexane. The organic phase was dried over anhydrous Na^sub 2^SO^sub 4^ and the solvent was distilled off to yield the essential oil.

GC and GC/MS: The oils were analyzed by using Varian Vista 6000 (DB-5, 30 m x 0.25 mm, FID) and Thermoquest Trace GC 2000 interfaced with Finnigan MAT Polaris Q Ion trap Mass spectrometer fitted with RTX-5 MS (Restek Corp.) fused silica capillary column (30 m x 0.25 mm; 0.25 µm film coating). The column temperature 60°-210°C was programmed at 3°C/min using He as carrier gas at 1.0 mL/min. The injector temperature was 210°C, injection size 0.1 µL, prepared in hexane, split ratio 1:40. MS were taken at 70 eV with mass range of m/z 40-450. Characterization was done on the basis of retention index, Library MS Search (NIST & Wiley), by comparing with the mass spectral literature data (8) and NMR (^sup 1^H- & ^sup 13^C-) of major isolates.

Fractionation/isolation of major constituents: The oils were fractionated by column chromatography (length 600 mm x 25 mm) on silica gel (120-240 mesh) packed in hexane and eluted with hexane followed by hexane-Et^sub 2^O mixtures. A total of 50 fractions were collected (in 5-25 inL fraction size). Fractions eluted in 15-25% ether in hexane gave four compounds - A, B, C, D (see Figure 1) - which were purified by HPLC on µ-Porasil column (Waters'; 25 cm x 7.8 mm size length; varying conc^sup n^, of Et^sub 2^O:hexane solvent; RI detector). The specific rotation (Perkin Elmer) and ^sup 1^H- and ^sup 13^C-NMR spectra (Bruker DRX-300 spectrometer) of compounds A, B, C, D were measured. It was observed that there were no qualitative changes in composition except minor variations in the concentration of constituents during different stages of growth of the plant.