In vitro antioxidant activities and antioxidant enzyme activities in HepG2 cells and main active compounds of endophytic fungus from pigeon pea [Cajanus cajan (L.) Millsp.]

This study evaluated the antioxidant activity of the main active compound of an endophytic fungus MD-R-1 from pigeon pea. This fungus was identified as Aspergillus fumigates by ITS sequence. The antioxidant capacity was evaluated by DPPH, hydroxyl radical scavenging, reducing power, lipid peroxidation and XOD inhibitory effect assays. Among the four fractions, the EtOAc fraction showed the best antioxidant activity (IC50 values were 16.38, 35.20, 19.69, 22.64 and 193.24 μg/mL, respectively) and the highest phenolic and flavonoid content. Furthermore, it possessed good protective activity from oxidative DNA damage. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) in HepG2 cells treated with MD-R-1 EtOAc extracts were also determined. The results showed that EtOAc extracts significantly increased the activities of SOD, CAT and GR in HepG2 cells in a dose-dependent manner. The LC-MS/MS was used to analyze EtOAc fraction and the result pointed to a notable antioxidant compound, luteolin. The present investigation suggests that MD-R-1 represents a valuable natural antioxidant source and may be applicable in health food industry potentially.