Abstract: In this study,15 endophytes with high antioxidant activity were selected from different tissues of Myricaria laxiflora pre- and post-flooding.To clarify the impact of polyphenols on the antioxidant capacity,the total polyphenol content(TPC) was screened by Folin-Ciocalteu method.MG-9,a strain with the highest TPC contents,was used to molecular identification and growth optimization.Based on the analysis of antioxidant capacity in vitro, the activity in vivo was also determined through the protective effects of MG-9 crude extracts to E.coli and human neuroblastoma cells SH-SY5Y under oxidative damage.The results showed that the TPC of MG-9 reached 148 mg/g in thallus and 270 μg/mL in fermentation broth,respectively.MG-9 was an Aspergillus sp. according to molecular and morphological identification.Exogenously adding a certain concentration of Mg²⁺ and K₊ to SDA medium can effectively promote the accumulation of TPC.The crude extracts had highly antioxidant activity,the radical scavenging rate of which got to 17% of vitamin C.Under oxidative stress,the crude extracts can increase the survival rate of E.coli cells by 245%,and 51.8% for human nerve cells.The further analysis indicated that the crude extract can protect the integrity of nerve cell membranes,and effectively reduce the LDH leakage rate.

Key words: Myricaria laxiflora, endophytic fungi, polyphenols, antioxidant