Optimization of supercritical fluid extraction of valuable compounds from Lagerstroemia speciosa leaves for in vitro antidiabetic and antioxidant activity

Abstract

This study reports, for the first time, the optimization of supercritical CO₂ extraction (SFE) of phenolic compounds from Lagerstroemia speciosa (LS) leaves using Response Surface Methodology (RSM), targeting both antioxidant and antidiabetic potential. Unlike conventional solvent-based extractions, SFE offers a green and tunable approach to recover thermolabile bioactive compounds. The extraction was optimized by varying pressure (20–40 MPa), temperature (70–110 °C), and time (30–70 min). The optimal conditions, 29.59 MPa, 89.50 °C, and 53.85 min, yielded 99.31 ± 2.57 mg GAE per g dry biomass of total phenolic content (TPC). Ultra Performance Liquid Chromatography-Photodiode Array detector (UPLC-PDA) analysis confirmed the presence of key phenolics such as p-hydroxybenzoic acid, vanillic acid, p-coumaric acid, chlorogenic acid, and vanillin. The extract exhibited strong enzyme inhibitory activity with IC₅₀ values of 30.09 ± 2.58 µg mL⁻¹ and 59.45 ± 3.40 µg mL⁻¹ against α-amylase and α-glucosidase, respectively, demonstrating its dual antioxidant and antidiabetic potential. These findings highlight LS leaves as a promising and underexplored source of bioactive compounds for the development of functional foods, nutraceuticals, and pharmaceutical applications.