Abstract:

This study evaluates the effect of seasonal variation and solvent polarity of Terminalia arjuna and Terminalia catappa leaf extracts on antioxidant and antidiabetic potential. The leaf samples were collected across three seasons and extracted with ethanol and acetone solvents. Antioxidant activity was assessed using DPPH free radical scavenging assay and ABTS radical cation scavenging assay, while antidiabetic potential was evaluated through α-amylase and α-glucosidase inhibition.
In the DPPH assay, T. arjuna ethanol showed lower IC₅₀ values of 0.225–0.280 mg/ml and acetone of 0.229–0.303 mg/ml, compared to ascorbic acid (0.1749 mg/ml). T. catappa ethanol exhibited higher IC₅₀ values of 0.514–0.719 mg/ml, and acetone 0.514–0.906 mg/ml. In the ABTS assay, T. arjuna ethanol showed lower IC₅₀ values of 2.096–2.558 mg/ml and acetone 2.202–2.743 mg/ml, comparable to Trolox (2.088 mg/ml), while T. catappa ethanol ranged from 3.875–5.293 mg/ml and acetone 3.881–5.413 mg/ml.
For antidiabetic activity, T. arjuna ethanol exhibited IC₅₀ values of 2.309–2.369 mg/ml and acetone 2.310–2.371 mg/ml for α-amylase, and 2.017–2.124 mg/ml (ethanol) and 2.063–2.136 mg/ml (acetone) for α-glucosidase, compared to acarbose (1.310 mg/ml and 1.127 mg/ml). T. catappa ethanol showed comparatively higher IC₅₀ values, ranging from 2.448–2.466 mg/ml and acetone 2.457–2.478 mg/ml for α-amylase, and ethanol 2.194–2.207 mg/ml and acetone 2.197–2.209 mg/ml for α-glucosidase.
GC–MS analysis of both species revealed bioactive compounds, including fatty acids (n-hexadecenoic acid, linoleic acid), phytosterols (γ-sitosterol, stigmasterol), and terpenoids (phytol), which contribute to free radical scavenging and enzyme-inhibitory activities. These findings highlight the significant influence of seasonal variation and solvent polarity on the therapeutic potential of Terminalia species.