Abstract: The antioxidant activity of 2,7-dihydroxy-3,6,9-trimethyl-9H-xanthene-1,4,5,8-tetraone (DTXT) was tested by reducing power, superoxide anion (O2-·), 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl radical (·OH) scavenging assays. The medium composition for DTXT production by Acremonium cavaraeanum CA022 in solid-state fermentation was optimized using one-factor-at-a-time method and response surface methodology (RSM). The results showed that the reducing power of DTXT at a concentration of 200 μg/mL was not significantly different from that of rutin, but higher than that of VE and BHT. DTXT could scavenge 67.00% of O2-·, 78.83% of ·OH and 76.53% of DPPH radical. The optimal medium formulation was obtained as follows: glucose 0.773%, sodium nitrate 0.185%, H3BO3 0.032%, and VB1 100 μg/100 g. It gave a DTXT yield of 4 150.80 mg/kg, which increased by 1.45 times compared with that before optimization (2 864.83 mg/kg).

Key words: 2,7-dihydroxy-3,6,9-trimethyl-9H-xanthene-1,4,5,8-tetraone; Acremonium cavaraeanum; free radical scavenging; single factor experiments; response surface methodology