Abstract: This study aimed to explore the effect of exogenous inducers on the biosynthesis and antioxidant properties of triterpenoids in Inonotus hispidus. We used seven inducers at different concentrations including methyl jasmonate (MeJA), salicylic acid (SA), oleic acid, willow branch decoction, Mn2+, Fe2+ and Cu2+. The results showed that all the seven inducers significantly promoted the mycelial growth of I. hispidus and the biosynthesis of triterpenoids, oleic acid being the most effective among these. A mycelial biomass yield of (7.146 ± 0.131) g/L was obtained by the addition of 3% oleic acid at the beginning of fermentation. The content of triterpenoids in the mycelia was (56.377 ± 3.178) mg/g, and the total production of triterpenoids was 402.870 mg/L, which was increased by 143.74% compared with the control group without any inducer added. The antioxidant tests showed that the antioxidant capacity of triterpenoids varied with inducer type. Among these inducers, oleic acid induced triterpenoids with the strongest antioxidant effect; the total reducing power was 1.342, and the IC50 values for scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl and superoxide anion radicals were 0.099, 1.294 and 0.001 mg/mL, respectively. The total reducing power and the free radical scavenging rates were increased by 79.48%, 66.71%, 28.10% and 29.22% compared with those of the control group, respectively. The results can provide scientific data for the application of inducers in the biosynthesis of triterpenoids and hence the development of new antioxidants.

Key words: Inonotus hispidus, submerged fermentation, triterpenoids, induction, antioxidant effect