Evaluation of Alpha-Amylase Inhibition by Catharanthus roseus and Azadirachta indica Leaf Extracts: An In Vitro Approach

Abstract

AbstractBackground: Type II diabetes mellitus specifically impairs glucose metabolism and poses severe health risks, with its prevalence rapidly rising in India. Conventional drugs like metformin and enzyme inhibitors manage blood sugar but often cause gastrointestinal side effects. α-Amylase inhibition has emerged as a targeted approach to control postprandial glucose spikes. Catharanthus roseus and Azadirachta indica, long used in traditional medicine, offer rich phytochemical profiles with proven antidiabetic potential. Methodology: Catharanthus roseus and Azadirachta indica fresh leaves were washed, shade-dried, powdered, and extracted with ethanol through Soxhlet extraction. A rotary evaporator was used to concentrate crude extracts to be analyzed further. Phytochemical screening revealed tannins, alkaloids, flavonoids, and glycosides. The starch-iodine colorimetric method was used in the assessment of alpha-amylase inhibition. Extracts and acarbose were assayed at 200-1000 μg/mL with the reaction incubated for 1 hour at 37°C. The enzyme inhibition was measured at 565 nm as a comparison between plant extracts and the standard drug acarbose. Result:  This study confirmed that the two plant extracts contained bioactive compounds, including glycosides, alkaloids, flavonoids, ds, and tannins. All samples exhibited dose-dependent inhibition of alpha-amylase, with the polyherbal blend achieving the highest efficacy (71.85% at 1000 μg/mL; IC₅₀= 534.39 μg/mL), approaching that of Acarbose (74.7%; IC₅₀= 513.97 μg/mL). The single plant extracts showed moderate inhibitory properties, and this shows the enhanced efficacy of a combination of these extracts in a synergistic manner. Conclusion: The current research demonstrates the strong antidiabetic activity of a polyherbal combination of Catharanthus roseus and Azadirachta indica. The starch-iodine method of quantifying alpha-amylase inhibition was dose-dependent, with the combined extract being more effective than the individual extracts. The findings indicate that such synergistic treatment can be effective in improving the treatment of type 2 diabetes, with the possible reduction of side effects associated with standard treatment