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Abstract
A detailed study on secondary metabolites from the stem bark of Garcinia dryobalanoides has yielded one triterpenoid and four xanthones. Along with that, five novel rubraxanthone derivatives had been successfully synthesised via Williamson etherification with various alkyl halides. The antibacterial evaluation on crude extract, isolated secondary metabolites (1-5), and synthesised compounds (6-9) against Lactiplantibacillus plantarum, Enterobacter cloacae, Pseudomonas aeruginosa, and Serratia marcescens demonstrated moderate to active activities outlining their bacteriostatic potential. The structure-activity relationship (SAR) study conducted revealed the presence of prenyl and hydroxy groups on the xanthone attributed to good bacterial inhibition. The introduction of the alkyl chain to the hydroxy part eventually decreases the antibacterial activity of the compound which is probably due to the bulkiness that causes steric hindrances, therefore limiting the ability to bind to its target site within the bacterial cell.
Graphical Abstract
Acknowledgments
The authors express our utmost gratitude to Universiti Malaysia Sarawak (UNIMAS) for providing financial funding under the PILOT research grant scheme (UNI/F07/PILOT/85386/2022) as well as research facilities and technical support. The Sarawak Biodiversity Centre (SBC) were also acknowledged.
Authors’ contributions
Conceptualisation, NHZ, ANAH, and VJYM; methodology, NHZ and NFZZ; Writing-original draft preparation, NFZZ, NHZ, ANAH; Supervision, NHZ, ANAH, NNS, and VJYM; All authors have read and agreed to the published version of the manuscript.
Disclosure statement
No potential conflict of interest was reported by the authors.