Phenolic content, antioxidant activities and antibacterial effects of Antidesma thwaitesianum Mull. Arg. extracts

Introduction: Antidesma thwaitesianum (Chinese name: 小斑五月茶, Pinyin: xiǎo yè wǔ yuè chá), taxonomically associated with its synonym Antidesma puncticulatum is a fruit rich in phenolic compounds known for their health benefits as well as their antibacterial and antioxidant activities. This study aimed to analyze the phenolic compound content and antioxidant activity of A. thwaitesianum extracts, as well as to investigate their inhibitory effects on the growth of Eschrichia coli, Aeromonas hydrophila, Bacillus spp. and Proteus mirabilis. Methods: The extracts were prepared by freshly squeezing the fruits and using 95 % ethanol as a solvent. The phenolic compound content was analyzed using the Folin - Ciocalteu method. Antioxidant activity was assessed using the DPPH assay, while antibacterial activity was evaluated using the disc diffusion method, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results: The results showed that A. thwaitesianum black fruit extract exhibited the highest total phenolic content (116.48 ± 2.8 mg GAE/g), while the strongest antioxidant activity (IC50 = 79.27 ± 1.88 mg/mL) occurred in red fruit water extract. whereas the red fruit ethanolic extract showed the strongest antibacterial activity with MIC values ranging from 0.98 - 250 µg/mL against tested bacteria. Discussion: Ethanol extracts of A. thwaitesianum especially from black fruits, contained higher phenolic content, while red fruit water extracts showed the strongest antioxidant activity and red fruit ethanol extracts exhibited the most potent antibacterial effects. These results highlight the potential of A. thwaitesianum as a natural source of antioxidant and antibacterial agents for functional food and phytopharmaceutical applications.