Comparative study of the volatile constituents of Thymus serpyllum L. grown at different altitudes of Western Himalayas

Thymus serpyllum L., a well-known aromatic plant of the Himalayan region is often used in pharmaceutical, cosmetic, flavoring and fragrance industries because of its phenolic and non-phenolic constituents. The amount of these compounds varies with the origin, the climatic conditions and the developmental stage of harvesting time of the plant. Under different environmental conditions, plant specimen of the same species respond differently through production and accumulation of the primary and secondary metabolites. In the present work, T. serpyllum L. was collected from its natural habitat and grown at different agro-climatic zones, i.e., Auli (higher Himalayas; 2744 m asl), Pithoragarh (lower Himalayas; 1524 m asl) and Haldwani (foothill areas; 412 m asl). The essential oil from fresh aerial parts of cultivated plants at full blooming stage was obtained using Clevenger apparatus and analyzed by GC–FID and GC–MS. The amount of thymol was also quantified by HPTLC. The data were statistically analyzed using MS Excel and SPSS 16.0. The percentage yield of the essential oils varied from 0.20 to 0.84%. Thymol was the major compound found in all the three cultivations, being the highest for Haldwani (84.63%) followed by Auli (50.80%) and Pithoragarh (41.15%) cultivations. Camphor was the second major compound, only identified in Pithoragarh (36.34%) region. Alpha-thujene, p-cymene, alpha-terpineol, (E)-caryophyllene, beta-bisabolene, alpha-pinene and carvacrol were also identified in significant amounts. HPTLC quantification suggested the similar pattern of thymol percentage as obtained from GC–FID. The study revealed that there was a significant difference in the terpenoid constituents of the plant grown at different agro-climatic zones. Thymus serpyllum grown at lower altitude area (warm climatic zone) can be a potential source of thymol along with high essential oil yield.