Gas Chromatography-Mass Spectrometry-Based Phytochemical Profiling and Bioactivity-Guided Fractionation of Psidium guineense Stem Extracts: In Vitro and In Silico Insights Into Antioxidant, Antidiabetic and Antibacterial Potentials

Abstract

Psidium guineense (Myrtaceae) is traditionally used for various medicinal purposes, although its stem remains underexplored. This study provides the first integrated phytochemical, pharmacological and computational evaluation of the stem extracts to elucidate their antioxidant, antidiabetic and antibacterial potential. The crude methanolic extract was fractionated with petroleum ether, dichloromethane, ethyl acetate and water. Preliminary phytochemical screening confirmed the presence of flavonoids, tannins, saponins, steroids, alkaloids, terpenoids and glycosides. Total phenolic and flavonoid contents were measured spectrophotometrically using the Folin–Ciocalteu reagent and the aluminium chloride colorimetric method, respectively. Antioxidant capacity was measured via 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, antidiabetic potential via α-amylase and α-glucosidase inhibition, and antibacterial activity via disc diffusion method. Gas Chromatography-Mass Spectrometry (GC-MS) profiling of the methanolic extract led to the identification of 28 phytoconstituents. Among all fractions, the dichloromethane fraction (DPG) exhibited the highest phenolic (247.94 ± 15.38 mg gallic acid equivalents/g) and flavonoid levels (510.27 ± 16.71 mg quercetin equivalents/g), along with superior DPPH radical scavenging capacity. DPG demonstrated scavenging activity (IC₅₀ = 7.45 ± 0.87 µg/mL) comparable to ascorbic acid. In enzyme inhibition assays, DPG showed remarkable α-amylase and α-glucosidase inhibitory effects (IC₅₀ = 22.28 ± 0.97 and 25.00 ± 2.01 µg/mL, respectively)—activities that surpass those reported for leaf extracts of related species. All fractions exhibited moderate, selective antibacterial activity against B. subtilis with zones of inhibition 7–16 mm. GC-MS profiling enabled tentative identification of compounds with reported antioxidant, antidiabetic and antimicrobial activities, supported by in silico docking showing strong predicted binding of selected tentatively identified constituents. These findings provide the first scientific investigation for the traditional use of P. guineense stem and highlight it as a previously unrecognized source of bioactive compounds warranting further isolation and characterization.