In vitro evaluation and comparison of antioxidant and antibacterial activities of leaf extracts of Hopea ponga (Dennst.) Mabberly

Abstract

Background: Hopea ponga has been categorised as an endangered tree species under International Union for Conservation of Nature red list of threatened species. Objective: To study the antibacterial, antioxidant activities, total phenolic and flavonoid contents of Hopea ponga leaf, extracted from different solvents viz., petroleum ether, chloroform and methanol. Materials and Methods: Antibacterial activity of leaf extract of Hopea ponga was determined by disc diffusion method against Escherichia coli, Proteus vulgaris, Bacillus cereus, Streptococcus faecalis and Pseudomonas aeruginosa. The antioxidant activities of the extracts were assayed through in‑vitro models such as 2,2‑diphenyl‑1‑picrylhydrazyl, 2,2’‑azino‑bis (3‑ethylbenzothiazoline‑6‑sulphonic acid), ferric reducing antioxidant power, hydrogen peroxide and hydroxyl scavenging activities. Total flavonoid content was determined using aluminium chloride colorimetric method and total phenolic content determined using Folin ciocaulteu reagent method. Results: Methanol extract showed higher scavenging activity against 2,2‑diphenyl‑1‑picrylhydrazyl and reducing power activity against ferric ion (97.24 ± 0.11 and 88.01 ± 0.03) compared to other extracts. Methanol extract showed significant antibacterial activity against P. vulgaris and B. cereus. Among the tested extracts, methanol extract exhibited higher content of phenols (1318.749 mg of ferulic acid equivalent/100 gram dry weight of extract) and flavonoids (457.832 mg of quercetin equivalent/100 gram dry weight of extract). Conclusions: The present study suggests that the methanol extract may contain active compounds, which have effective antioxidant and antimicrobial activity. Hence, this endangered species have to be explored and conserved to serve the mankind. Key words: Antioxidant, antimicrobial, dipterocarpaceae, Hopea ponga, total phenolic, total flavonoid