Phytopharmacological insights into the endodermis and exodermis of Terminalia chebula fruits: antioxidant, antihyperlipidemic, and antidiabetic activities
摘要
Terminalia chebula Retz., a polyphenol-rich medicinal fruit, exhibits layer-specific bioactivities relevant to metabolic disorders. In vitro antioxidant assays report potent activity for layer-specific extracts, DPPH inhibition up to 96% (ethanolic extract) and IC50 values as low as 2.08 µg mL−1 (methanolic fraction) and 3.15 µg mL−1 (neuroprotective DPPH value) for selected fractions. Enzyme inhibition assays show strong suppression of α-glucosidase and α-amylase (reported IC50 ≈ 0.19 µg mL−1 for methanol–water extracts in one study). In vivo rodent models demonstrate dose-dependent glucose lowering (e.g., 200 mg kg−1 aqueous extract ~ 46.8% reduction in OGTT peak glucose; chronic dosing reduced fasting glucose from 253 ± 9.4 to 123 ± 8.4 mg dL−1) and improved lipid parameters (reductions in total cholesterol and LDL-C reported across studies). Comparative analyses suggest the endodermis is relatively enriched in small, highly scavenging polyphenols. In contrast, the exodermis concentrates hydrolyzable tannins (e.g., chebulagic/chebulinic acids) that favor enzyme inhibition and lipid-modulating activity. A randomized, placebo-controlled human trial using an aqueous T. chebula extract (500–1000 mg/day) reported improvements in endothelial function, inflammatory markers (CRP, IL-6) and lipid profile over 12 weeks. We highlight current methodological limitations (heterogeneous extraction protocols, absence of standardized layer sampling, and limited clinical data) and propose standardized reporting (IC50, % inhibition, extraction solvent, dose ranges) and layer-specific clinical studies to enable translation of these anatomical phytopharmaceuticals.
Graphical abstract