Phytochemical composition, antioxidant capacity, and antidiabetic potential of various leaf extracts of Garcinia lanceifolia Roxb.

Introduction: Garcinia lanceifolia Roxb. has been used to manage metabolic disorders such as diabetes. This study investigated the impacts of aqueous and graded ethanolic extracts on the phytochemical composition, antioxidant capacity, and antidiabetic efficacy of G. lanceifolia leaves. Methods: Leaves were extracted via aqueous decoction and ethanol maceration at 25%, 50%, 75%, and 95% concentrations. Qualitative screening identified phytochemicals, while total phenolic content (TPC) and total flavonoid content (TFC) were quantified. Significant bioactive components were examined utilizing gas chromatography-mass spectroscopy (GC-MS). The antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. In vitro α-glucosidase and α-amylase inhibition assays were conducted. Results: Alkaloids, saponins, and terpenoids were consistently present, while tannins and steroids appeared in 75-95% ethanol extracts. The 95% ethanol extract showed the highest TPC (20.62 ± 0.61 mg gallic acid equivalent/g) and TFC (65.92 ± 1.76 mg quercetin equivalent/g), and GC-MS identified multiple pharmacologically active compounds. This extract exhibited the strongest antioxidant activity in DPPH (379.07 ± 1.33 mg Trolox equivalent/g) and ABTS (12.56 ± 1.00 mg Trolox equivalent/g) assays. Enzyme inhibition was concentration-dependent, with IC₅₀ values of 0.533 ± 0.098 mg/mL for α-glucosidase and 0.286 ± 0.031 mg/mL for α-amylase. Conclusion: Extraction with high-concentration ethanol enhanced the recovery of bioactive compounds, resulting in superior antioxidant and antidiabetic activities. These findings support its traditional use and highlight ethanolic extracts as potential natural agents for managing diabetes and oxidative stress. Further studies should isolate individual compounds and evaluate their in vivo efficacy.