Cytotoxic and Antibacterial Properties of Resveratrol Oligomers from the Stem Bark of Dryobalanops rappa

Background: Dryobalanops rappa is a plant species belonging to the family of Dipterocarpaceae. Nevertheless, the active compounds present in D. rappa have never been investigated. Objective: The aim of this research is to isolate and characterize compounds from Dryobalanops rappa and to study its bioactivity against human MCF-7 breast cancer and A549 lung cancer cell lines and several bacterial strains. Methods: The isolation step was carried out using a combination of chromatographic techniques. The structure of the isolated compounds was elucidated mainly using NMR spectroscopy. The cytotoxic activity of isolated compounds was determined with MTT assay, and the antimicrobial was screened using a modified resazurin microtiter-plate assay. Results: Isolation and purification of methanolic extract of D. rappa stem bark yielded 14 known oligomeric resveratrol types of compounds (1-14). Results showed that isolated ampelopsin E (5) and vaticanol C (14) displayed moderate activity against human MCF-7 breast cancer and A549 lung cancer cell lines with IC50 values 14.3 and 10.7 μg/mL, respectively. Interestingly, acetate derivative of isolated laevifonol (2) and ampelopsin F (3) was found to possess potent activities towards MCF-7 cancer cell line with IC50 values 2.8 and 3.3 μg/mL, respectively, in comparison to the parental compounds that demonstrated weak activities (IC50 > 50 μg/mL). For the antibacterial assay, compounds 10 and 12 showed moderate activities towards Gram-positive bacterial strains (MIC ≤ 50 μM). Conclusion: 14 known oligomeric resveratrol types of compounds have been isolated. The activity of 14 against A549 cell line, 5 against MCF-7 cell line, and 10 and 12 against Gram-positive bacterial strains were the most promising results of this study. While the strong cytotoxicity of acetate derivative (2 and 3) against MCF-7 cell line has revealed the potential of resveratrol oligomers to be used as a template for designing new anticancer drugs.