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.

Origanum vulgare L., the most complex and variable species of the genus Origanum, is used to cure various diseases in the traditional medicinal system. In the current investigation, O. vulgare was collected from its natural origin and further multiplied for two years at the experimental farm of DIBER field station, Auli, and afterwards, it was grown at three different altitudes, i.e., DIBER field station of Auli (2744 m), Pithoragarh (1524 m), and Haldwani (412 m), under natural field conditions. The essential oil was extracted using the Clevenger apparatus and analyzed by GC/MS and GC/FID. The total phenolic, flavonoid, and tannin content in the methanolic extracts of all the cultivations were estimated by using Folin–Ciocalteu reagent, aluminium chloride reagent, and Folin–Denis methods, respectively. The antioxidant activity of the essential oils and extracts of all the cultivations was also estimated by DPPH, ABTS, and reducing power methods. The highest amount of phenolics, flavonoids, and tannins was obtained in the Pithoragarh cultivation. Thymol was the major component in all the essential oils contributing 38.81% (Auli), 52.83% (Pithoragarh), and 31.86% (Haldwani) of the total oil. The highest antioxidant activity was exhibited by oregano oil of Pithoragarh cultivation, followed by Auli and Haldwani, respectively. The alcoholic extract of Pithoragarh cultivation had the highest antioxidant activity. The study infers that the plant demonstrated good results in terms of fresh weight, oil yield, antioxidant potential, and EO composition when grown at higher altitudes.

In-vitro antioxidant activity of therapeutically important plant Thymus serpyllum L. grown at different altitudes viz. foothill areas, lower Himalayan and higher Himalayan regions were evaluated against various radicals such as DPPH, ABTS and reducing power assays. The antioxidant constituents like total phenols, flavonoids and total tannins were also evaluated in the present study. The results revealed that the alcoholic, as well as the aqueous extracts of the plant, showed significant antioxidant potential against all the radicals. Extracts obtained from different altitude cultivation showed variation in IC50 values. The alcoholic and aqueous extracts prepared from the plants grown at foothill areas (Haldwani) showed the highest DPPH (IC50: ALC-0.566 mg/ml; AQ- 0.778 mg/ml), ABTS (IC50: ALC- 0.484 mg/ml; AQ- 0.533 mg/ml) and reducing power (EC50: ALC- 0.29 mg/ml; 0.42 mg/ml) activities, followed by high altitude cultivated plants, (Auli), with moderate antioxidant activity. The extracts from mid-altitude cultivation (Pithoragarh) exhibited the least antioxidant potential. The results showed that the amount of total phenolics and flavonoids were significantly correlated to the antioxidant activity. Higher the value of phenolics (TS3: 12.63mg CE/g> TS1: 11.51 mg CE/g> TS2: 10.70 mg CE/g) and flavonoids (TS3: 9.30 mg QE/g> TS1: 9.07mg QE/g> TS2: 6.59mg QE/g) in the extracts, greater was the antioxidant activity. Therefore, T. serpyllum grown in foothill areas was more beneficial in preparing various herbal formulations.