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Characterization of the Essential Oil Composition of Isodon rugosus (Wall. ex Benth.) Codd. from Garhwal region of Western Himalaya

Verma RS, Pandey V, Chauhan A and Tiwari R

Background: Isodon rugosus belongs to the family Lamiaceae and is an important aromatic shrub, distributed widely throughout the northern temperate regions of the Himalaya. Regardless of the various traditional usage and diverse biological activities, little data exists on the essential oil composition of I. rugosus populations. This study aimed to characterize the essential oil of I. rugosus collected from two locations (Ghangaria and Tapovan) of Garhwal region of western Himalaya for occurrence of new composition.

Methods: The shade dried plant materials were hydrodistilled in a Clevenger’s type apparatus for 3 h for isolation of their essential oils. The resulting essential oils were analysed using gas chromatography-flame ionization detector (GC-FID) and GC-mass spectrometry (GC-MS).

Result: Altogether, 92 constituents, comprising 83.9-92.6% of the total oil compositions were identified. Major constituents of the oil were α-pinene (0.8-19.3%), trans-ferruginol (3.0-17.1%), α-phellandrene (2.6- 10.5%), (E)-caryophyllene (4.0-9.3%), germacrene D (1.9-8.8%), abietatriene (1.9-5.3%), β-phellandrene (3.1-4.4%), δ-cadinene (2.9-3.6%), limonene (1.3-3.6%), myrcene (0.2-3.6%) and p-cymene (2.9-3.5%). The examined oil was considerably different in respect of their qualitative and quantitative compositions compared to earlier studies. Moreover, to the best of our knowledge, 52 constituents, including trans-ferruginol, abietatriene, totarene, phyllocladene, 4-epi-abietal, caryophyllene acetate, cubenol, allo-hedycaryol, δ-amorphene, transcadina- 1 (6),4-diene, cis-cadina-1 (6),4-diene, α-muurolol, amorpha-4,9-dien-2-ol, (Z)-nuciferol acetate and viridiflorol were reported for the first time in I. rugosus essential oil.

Conclusion: The dominant presence of sesquiterpenoids and diterpenoids in the ‘Ghangaria’ population and monoterpenoids and sesquiterpenoids in the ‘Tapovan’ population made them novel compositions. The newly identified constituents, especially diterpenoids can be of chemotaxonomic significance.