Comprehensive phytochemical profiling, antibacterial, antioxidant, and in-silico evaluation of Aster thomsonii C.B. Clarke essential oil from the Kumaun Himalaya Region, Uttarakhand

The present work aimed to perform the first comprehensive investigation on Aster thomsonii C.B. Clarke essential oil from the Kumaun region of Uttarakhand, India, examining its chemical composition, antibacterial, antioxidant activities, and molecular docking potential against key bacterial targets. The essential oil extracted via hydro-distillation with a yield of 0.3% v/w, corresponding to 0.3 mL per 100 g of fresh aerial parts and analysed by GC-MS, revealed forty-five compounds with β-selinene (21.10%), β-caryophyllene (11.26%), geranyl isobutyrate (9.47%), α-humulene (8.93%), and cis-α-bisabolene (8.89%) as major constituents. The oil exhibited concentration-dependent antibacterial activity, with minimum inhibition zones ranging from 5.3 ± 0.57 to 7.6 ± 1.15 mm. The Minimum Inhibitory Concentration (MIC) values ranged from 6.25 to 25 µL/mL. The MIC of 6.25 µL/mL was observed against S. aureus, P. mirabilis, and X. oryzae, whereas R. solanacearum exhibited an MIC of 12.5 µL/mL and P. aeruginosa showed an MIC of 25 µL/mL. Antioxidant assays yielded IC₅₀ values of 32.22 µL/mL (DPPH•) and 31.08 µL/mL (H₂O₂). The molecular docking identified α-cadinol, longicyclene, germacrene D, cubenol, and β-caryophyllene as strong binders (-6.6 to -8.6) kcal/mol, highlighting A. thomsonii essential oil as a promising source for drug discovery, antimicrobial and antioxidant therapeutics, and pharmacological applications.