Antioxidant and antimicrobial activities of shorea kunstleri

Objective: To evaluate antioxidant and antimicrobial activities of stembark of Shorea kunstleri together with analysis of phytochemical and total phenolic contents. Methods: Extraction was conducted with different solvent polarity of n-hexane, dichloromethane (DCM) and methanol by using Soxhlet extraction. Total phenolic content was determined using Folin-Ciocalteu method. Free radical scavenging activity and inhibition of lipid peroxidation were evaluated with DPPH radical scavenging and ferric thiocyanate (FTC) assays, respectively. Antimicrobial activities were performed using disc diffusion method, minimum inhibition concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC). Results: S. kunstleri stembark extracts revealed presence of steroids, terpenoids, saponins, flavonoids, and phenolic compounds. Methanol extract exhibited the highest total phenolic content and free radical scavenging activity result in phenolic content of 8.34±0.003 g GAE/100 g of extract and 95.9±1.07% DPPH inhibition (IC50 value of 18.6 µg/ml), respectively. FTC assay of n-hexane, DCM, and methanol extracts indicated lipid peroxidation inhibitory activity of 74.2±0.35%, 74.0±0.10%, and 72.8±0.27%, respectively. In antimicrobial and antifungal tests, methanol extract showed inhibition against S. aureus, C. albicans, and C. tropicalis with inhibition zones of 10-12, 18-22, and 18-19 mm, respectively. The MIC test of methanol extract showed highest inhibition against C. albicans and S. aureus (0.04 and 0.08 mg/ml, respectively) while DCM extract exhibited the highest activity towards C. tropicalis (MIC value of 0.63 mg/ml). Taken together, MBC test of methanol extract strongly demonstrated bactericidal effect against S. aureus with MBC value of 0.08 mg/ml. Conclusion: The study demonstrated that stembark extracts of S. kunstleri possessed antioxidant and antimicrobial properties