ASSESSMENT OF IN VITRO PHENOLIC CONTENT AND ANTIOXIDANT CAPACITY OF DIOSPYROS PHILIPPINENSIS A.DC. (EBENACEAE) METHANOLIC LEAF EXTRACT

Estela P. De Vera, Librado A. Santiago

Abstract


The aim of the study was to assess the phenolic content and potential free radical scavenging activities of Diospyros philippinensis, A.DC., an endemic medicinal plant in the Philippines. Methanolic extraction of the leaves yielded 23% crude extract. Phytochemical screening revealed the presence of alkaloids, flavonoids, saponins, steroids, anthraquinone heteroside and tannins. The methanolic rude extract (MCE) exhibited concentration-dependent response against DPPH (IC50<0.098 mg/mL), nitric oxide radical (IC50=0.441±0.001 mg/mL) and hydrogen peroxide (IC50=0.179± 0.001 mg/mL) assays. The highest concentration (6.25 mg/mL) of MCE was subjected to Ferric-reducing antioxidant power assay (FRAP) and gave 84.23±0.002% reducing power. Assessment of total phenolic and flavonoid content yielded 57.72±0.001 mgGAE/g) and 28.87±0.002 mgQE/g, respecctively. Furthermore, MCE was partitioned using solvents with increasing polarity. Each solvent fraction was subjected to TPC and TFC determination. Ethyl acetate fraction (EF) gave the highest phenolic (31.92±0.001 mgGAE/g) and flavonoid (8.66±0.001 mgQE/g) content. The fractions were subjected further to column chromatography. EF and Ethyl acetate subfraction 6 (ESF6) exhibited concentration-dependent response against various free radicals and gave significantly high reducing power. HPLC study identified two phenolic compounds, gallic acid and quercetin, in MCE (18.86±0.08 mgGA/g; 0.658±1.03 mgQ/g) and EF (10.10±0.08 mg GA /g; 0.059±1.03 mgQ/g) and ESF6 (6.86±0.08 mgGA/g). No peak for quercetin was detected in ESF6. These findings provide a direct link that gallic acid and flavonois are the key phytochemicals in D. philippinensis most likely responsible for its antioxidant and free radical scavenging activities.

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