Mechanistic Insights into the Antioxidant and Antidiabetic Potential of Longan (Dimocarpus longan L.) Fruit Peel

Abstract

Valorization of fruit peel offers a sustainable approach to extracting bioactive compounds with therapeutic potential. This study assesses the antioxidant and antidiabetic properties of longan peel extract (LPE). Antioxidant activity was determined using radical scavenging (superoxide, nitric oxide, and hydroxyl) and reducing assays (FRAP and phosphomolybdenum). The antidiabetic potential was determined by enzymatic assays (alpha-amylase and alpha-glucosidase) and a non-enzymatic assay (glucose uptake by yeast cells). The bioactive compounds were identified using Gas Chromatography-Mass Spectrometry (GC-MS). LPE exhibited concentration-dependent free radical scavenging activity, with the highest activity for nitric oxide (IC50 value = 15.03 µg/mL), followed by superoxide (IC50 value = 20.57 µg/mL) and hydroxyl radical scavenging (IC50 value = 97.68 µg/mL). The reducing power also increased in a concentration-dependent manner. Enzymatic inhibition assays showed an IC50 value of 28.59 µg/mL for alpha-amylase and 8.57 µg/mL for alpha-glucosidase. Glucose uptake by yeast cells increased linearly across all tested concentrations (5, 10, and 25 mM). GC-MS analysis detected various compounds, with the predominant compounds being 13-Docosenamide (40.25%), α-D-glucopyranoside (14.13%), hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester (4.73%), benzoic acid, 4-ethoxy-, ethyl ester (4.60%), myristic acid (2.17%), geranylgeraniol (0.90%), and deoxyspergualins (0.65%). These findings highlight the antioxidant and antidiabetic properties of LPE; however, further research is needed to isolate bioactive compounds and determine their therapeutic potential.