Diospyros kaki (Dk) leaves have been used in China, Korea and Japan as a delicate, pleasant beverage.
Additionally, it is used as a folk remedy for hypertension, ischemic stroke, angina
and internal hemorrhage. However, in EU and particularly in Portugal Dk leaves are considered an agriculture
waste. The aim of this study was to characterize methanolic Dk leaf extract concerning
its in vitro antioxidant proprieties and evaluate eventual cytotoxic effects, using HepG2 cells
(hepatocytes). HPLC-DAD profiles of Dk leaves showed that extracts are mainly composed
by phenolic compounds (flavonoids and phenolic acids derivatives), known antioxidants.
To assess antioxidant potential, we used several in vitro tests including DPPH scavenging, iron chelation, inhibition of nitric oxide and superoxide
scavenging. Results showed that Dk have a high capacity to scavenge superoxide radicals
(EC50 8.94 µg/ml), even better than quercetin (EC50 18.73 µg/ml), and DPPH radicals (EC50 15.27 µg/ml). For iron chelating activity and inhibition of nitric oxide production
Dk extract had lower potential with and EC50 of 1376 and 1027 µg/ml, respectively. So, we can conclude that Dk leaf extract is a good radical scavenger and might protect
cells from oxidative stress. Since Dk leaves are used in beverages and liver is always
a key target organ for metabolization and detoxification, we tested possible cytotoxicity
on HepG2 cells. Results did not show significant cytotoxic effects of Dk extracts
on HepG2 cells (using MTS evaluation), up to 1 mg/ml, for 3 and 24h incubation times.
Hence, we can infer that Dk leaf extracts have good antioxidant potential and no significant
toxicity (at least on hepatocytes), however more tests are required with other cellular
models.
This work was supported by project HEALTHKAKI, N° 010672, Programa Operacional Regional
do Norte, no âmbito do Portugal 2020.
