Investigation of In Vitro Anti-diabetic Activity and Phenolic Component Profile of Mulberry Leaf Tinctures

This study aimed to evaluate the in vitro anti-diabetic potential and phenolic compound profile of leaf tinctures prepared from fresh and dried leaves of three mulberry species (Morus alba L., Morus rubra L., and Morus nigra L.) using different plant-to-solvent ratios, with the objective of identifying the most effective formulation for Type II diabetes. For this purpose, ethanol:water (70:30, v/v) tinctures were prepared at 1:4, 1:5, 1:6, 1:7, and 1:8 (w/v) ratios, and their inhibitory activities against α-amylase and α-glucosidase enzymes were determined by a spectrophotometric method. Among all tested samples, the dried M. rubra L. leaf tincture prepared at a 1:6 ratio (TMrD 1:6) exhibited the strongest inhibitory activity, with IC₅₀ values of 24.11 μg/mL for α-amylase and 40.18 μg/mL for α-glucosidase. The phenolic compound profile of the most active tinctures was further investigated using high-performance liquid chromatography coupled with diode-array detection (HPLC-DAD) through the screening of 42 phenolic compounds. Protocatechuic acid, p-hydroxybenzoic acid, caffeic acid, and chlorogenic acid were quantitatively detected, whereas p-coumaric acid, ferulic acid, coumarin, and trans-cinnamic acid were present only in trace amounts. Overall, the dried M. rubra L. leaf tincture (TMrD 1:6) demonstrated promising potential as a phytopharmaceutical candidate for diabetes management.