Antibacterial and antioxidant potential of Aesculus indica (Wall. ex cambess.) Hook. leaf extracts along an altitudinal gradient in the Garhwal Himalaya

Aesculus indica (Indian Horse Chestnut), a medicinal plant native to the Himalayan moist temperate forests, was investigated for its antibacterial and antioxidant properties across different altitudes. Leaf samples were collected from three sites in the Garhwal Himalaya: Khirsu (1807 m ), Adwani Forest (2109 m ), and Kanchula-Kharak (2637 m ). Sequential extraction using acetone, methanol, and water was performed. Antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was assessed via agar well diffusion, while antioxidant capacity was measured using DPPH, FRAP, and ABTS assays. GC-MS analysis identified key phytochemicals and their variation with altitude. The methanol extract from the highest altitude (Kanchula-Kharak) demonstrated the most potent antibacterial activity against Staphylococcus aureus , with a maximum inhibition zone of 22.33 ± 1.53 mm and the lowest MIC (7.50 mg/mL) and MBC (15 mg/mL) values observed in the acetone extract. Antioxidant assays revealed the highest DPPH scavenging (IC 50 27.87 ± 4.47 μg/mL) and ABTS inhibition (94.46 ± 1.27 %) in Kanchula-Kharak extracts, while the Adwani Forest methanol extract exhibited the highest FRAP value (62.65 ± 1.97 mmol Fe 2+ E/mg). GC-MS profiling revealed diverse phytocompounds, primarily triterpenoids, fatty acids, lipids, and hydrocarbons. Both antibacterial and antioxidant activities increased significantly with altitude. These findings suggest that altitude positively influences the medicinal potential of A. indica , highlighting potential harvesting sites and their value for herbal formulation. • Altitude boosts antioxidant and antibacterial potential in Aesculus indica leaves. • GC-MS shows altitude-specific metabolite changes affecting bioactivity. • Altitude influences phytochemical distribution in Aesculus indica leaves. • Results support conservation and medicinal use based on altitude variation.