South Asian Research Journal of Natural Products

Aims: The objective of this study is to isolate antibacterial substances from the ripe fruit extract of Garcinia xanthochymus and to evaluate their toxicity through a brine shrimp lethality assay.

Study Design: The research involved the collection of ripe fruits, followed by the isolation of active substances and subsequent biological activity assessments.

Place and Duration of Study: Ripe fruits of G. xanthochymus were collected in July 2022 from Ratchaburi Province, Thailand. The experiment work was conducted at the Department of Medical Sciences from July 2022 to September 2024.

Methodology: The isolation of active substances was conducted following the bioassay-guided separation principle. Biological activity evaluations were performed using the broth microdilution assay and the brine shrimp lethality assay.

Results: Benzophenones were isolated from the ethyl acetate extract of G. xanthochymus fruits, identified as the primary antibacterial agents. The isolated substances include guttiferone E (1a), xanthochymol (1b), isoxanthochymol (2a), and cycloxanthochymol (2b). These substances exhibited antibacterial activity against Streptococcus mutans, with minimum inhibitory concentrations (MICs) in the range of 6.25-12.5 µg/mL. Toxicity assessments indicated that guttiferone E (1a)/xanthochymol (1b) displayed brine shrimp toxicity, with a lethal concentration 50% (LC₅₀) value of 3.67 µg/mL. Conversely, isoxanthochymol (2a)/cycloxanthochymol (2b) demonstrated a much lower toxicity profile, with LC₅₀ value exceeding 1,000 µg/mL.

Conclusion: The isolated benzophenones exhibited remarkable antibacterial activity against S. mutans, with MICs comparable to tetracycline. Additionally, the cyclized derivatives (2a and 2b) showed enhanced antibacterial activity and lower toxicity. These findings suggest the potential of isoxanthochymol (2a) and cycloxanthochymol (2b) for future antibacterial applications.