Gas Chromatography-Mass Spectroscopic Profile, In vitro Antidiabetic and Radical Scavenging Potentials of Polyalthia longifolia leaf phenolic extract

Reactive radicals are pivotal in the pathogenesis and progression of many diseases including diabetes mellitus. Medicinal plants are globally recognized as viable alternative sources of bioactive compounds for the management of such diseases. Polyalthia longifolia (Masquerade tree) remains relatively untapped for therapeutic bioactive compounds for the management of diabetes mellitus. This study aimed to evaluate the radical scavenging and antidiabetic potentials of Polyathia longifolia leaf phenolic extract (PLLPE) in vitro. PLLPE was obtained by soaking 150 g of the air-dried pulverized leaf of P. longifolia in 1500 ml of two-phase solvent system (ethyl acetate, acetic acid and water 3:1:6 v/v/v) for 1 hour as described in literature. This yielded 1.3 g of crude phenolic extract, equivalent to 0.92 %w/w. α-amylase and α-glucosidase inhibitory activity of the extract and nitric oxide, 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS*), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH*), and hydroxyl radical scavenging potentials were assayed using standard methods with acarbose and butylated hydroxytoluene (BHT) as standards. The gas chromatography-mass spectrometric (GCMS) profile of the extract was also determined. The percentage radical scavenging and inhibitory activities of PLLPE increased with concentration across the parameters determined. The IC50 for the inhibition of α-amylase by the PLLPE was lower (269.712 µg/ml) compared to acarbose (434 µg/ml) while the IC50 for the inhibition of alpha glucosidase by the PLLPE was higher (122.64 µg/ml) compared to acarbose (45.60 µg/ml). Though the percentage radical scavenging activity of PLLPE increased with concentration, it only possessed a lower SC50 for scavenging against hydroxy radical (178 µg/ml) compared to BHT (337.40 µg/ml). GCMS analysis of the extract revealed thirty-one compound peaks, out of which 2,3-dihydro-2-Benzofuran, (34.33), 2,3-dihydro-3,5-dihydroxy-6-methyl- 4H-Pyran-4-one (10.40), Methoxyacetic acid, 2-propenyl ester (7.29) and 2-Pyridinecarboxaldehyde (5.72) were the most abundant. Thus, PLLPE contains promising constituents for the management of diabetes mellitus.