Stimulatory Agents Simultaneously Improving the Production and Antioxidant Activity of Polyphenols from Inonotus obliquus by Submerged Fermentation.

Polyphenols are important secondary metabolites from the edible and medicinal mushroom Inonotus obliquus. Both the rarity of I. obliquus fruit body and the low efficiency of current method of submerged fermentation lead to a low yield of polyphenols. This study was aimed to determine the effect of applying stimulatory agents to liquid cultured I. obliquus on the simultaneous accumulation of exo-polyphenols (EPC) and endo-polyphenols (IPC). Linoleic acid was the most effective out of the 17 tested stimulatory agents, the majority of which increased the EPC and IPC production. The result was totally different from the stimulatory effect of Tween 80 for polysaccharide production in previous studies. The addition of 1.0 g/L linoleic acid on day 0 resulted in 7-, 14-, and 10-fold of increase (p < 0.05) in the production of EPC extracted by ethyl acetate (EA-EPC), EPC extracted by n-butyl alcohol (NB-EPC), and IPC, and significantly increased the production of ferulic acid, gallic acid, epicatechin-3-gallate (ECG), epigallocatechin-3-gallate (EGCG), phelligridin G, inoscavin B, and davallialactone. The EA-EPC, BA-EPC, and IPC from the linoleic acid-containing medium had significantly (p < 0.05) stronger scavenging activity against 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH), which was attributed to the higher content of these bioactive polyphenols.