Variation in secondary metabolite content in Aesculus indica (Wall. ex Cambess.) Hook. leaves along the altitudinal gradient in Indian Central Himalaya

Aesculus indica (Wall. ex Cambess.) Hook. a deciduous tree native to the Himalayan region, is renowned for its medicinal attributes and harbors a diverse array of phytochemicals that contribute to its therapeutic potential. The present study aimed to investigate the impact of altitude on the phytochemical content of A. indica leaves. Therefore, the leaves sample were collected from three different altitudes of the Garhwal Himalayan region and extracted using three distinct polarities of solvents (Distilled water, Methanol and Acetone). Phytochemical screening included both preliminary qualitative and quantitative analysis. The preliminary qualitative analysis showed the presence of various secondary metabolites, including phenol, flavonoid, tannin, saponin, steroid and glycoside, while the alkaloid remained absent. Quantitative analysis displayed the highest amount of total phenol 124.50 ± 1.73 mg GAE g⁻¹ Dw, total flavonoid 717.70 ± 0.60 mg QE g⁻¹ Dw, total tannin 342.47 ± 8.55 mg TAE g⁻¹ Dw and total flavonol content 250.69 ± 12.79 mg RE g⁻¹ Dw in sample collected from the highest altitude at Kanchula Kharak (2637 m asl). A significant variation (p ≤ 0.05) was seen in secondary metabolite content with changing altitude; total phenol, flavonoid and flavonol content showed a strong positive correlation (p < 0.001) with altitude, while tannin content exhibited a weaker correlation. Additionally, methanol extracts displayed a higher affinity towards the phenol content, whereas acetone extracts favored flavonoid, tannin, and flavonol content. In contrast, distilled water extracts consistently exhibited the lowest concentrations of all estimated phytochemicals. Although this is the first study investigating the influence of altitudes on the secondary metabolite content of A. indica, these findings contribute baseline information for determining the optimal location for harvesting a high quantity of specific compounds, in particular A. indica, for the formulation of herbal commodities.