Biotransformation of Chinese Jujube with Cordyceps militaris to Enhance the Antioxidant Activity In Vitro and the Protective Effect against Ethanol-Induced Oxidative Stress in Zebrafish

Solid-state fermentation (SSF) of Chinese jujube with Cordyceps militaris was performed in the present study. The results revealed that the contents of total phenolic and flavonoid in rice medium with 50% jujube content increased to 1.59 mg GAE/g d.w. and 0.46 mg RE/g, respectively. The changes of phenolic acid composition showed a similar tendency, and three forms of individual phenolic compounds, namely free phenol, free/conjugated phenol, and bound phenol increased with the extension of the fermentation time. The determination of DPPH, ABTS, FRAP, and the ferrous ion chelating capacity showed that the fermentation significantly enhanced the antioxidant activity in vitro, and the protective functions against ethanol-induced oxidative stress in zebrafish were also then investigated. SSF co-treatment with EtOH reduced MDA elevation and enhanced the activities of SOD and GSH-Px, along with the T-AOC levels in a dose-dependent manner in adult and larval zebrafish. Moreover, the qRT-PCR findings demonstrated that SSF-jujube was capable of upregulating the mRNA expressions of Nrf2 and HO-1 and downregulated the levels of NF-κB in zebrafish larvae. In conclusion, solid-state fermented Chinese jujube with C. militaris was an effective process, exhibited a good antioxidant activity, and demonstrated a better protective effect against ethanol-induced oxidative stress.