Anti-oxidant and anti-bacterial effects of Diospyros kaki leaf extract in Vietnam

Diospyros kaki is a famous commercial plant with its edible fruit (persimmon) and is widely used as a traditional remedy in Vietnam. However, the anti-oxidant and anti-bacterial effects against gastrointestinal microbes of the D. kaki leaf extract have not been elucidated yet. In this study, the methanol extract from D. kaki leaves contained some chemical groups, such as tannins, flavonoids, phenolic compounds, alkaloids, and saponins, mainly it was rich in polyphenols and flavonoids (528.11 ± 12.96 mg GAE/g and 44.49 ± 6.77 mg QE/g, respectively). The extract exhibited a strong anti-oxidant ability (DPPH scavenging activity of about 91.83 ± 1.02% and total anti-oxidant capacity of approximately 110.58 ± 2.65 mg AAE/g). Furthermore, the anti-bacterial activity of the extract against some gastrointestinal bacteria, including Staphylococcus aureus, Enterococcus durans, Enterococcus faecium, and Yersinia enterocolitica, has been reported for the first time (the zone of inhibition ranging from 14.17 - 24.67mm). MIC of the extract was 0.6125 - 1.25 mg/mL, and MBC was 2.5 - 5 mg/mL, which implied the extract exerted a bactericidal effect. These findings suggest D. kaki leaf extract is a promising source of extracting bioactive compounds, such as anti-oxidant and anti-microbial agents, and a potential medicine for the treatment of gastrointestinal infections.