Analysis of radical scavenging active constituents in the mycelia of Isaria gracilioides

Abstract:

A DPPH-microplate assay was employed for quantitative analysis of the free radical scavenging activity of the extracts extracted with different solvents from mycelia of Isaria gracilioides. The results showed that the methanol extract had the strongest free radical scavenging activity. At the concentration of 10 mg mycelium per milliliter methanol, the radical scavenging rate of the extract reached 92.4%±0.3%. The results of DPPH-TLC assays showed that the methanol extract contained four main free radical scavenging components. The combined LC-DAD-HRMS and DPPH assay revealed that the molecular formulas of the four free radical scavengers were possibly C15H16NO3 (1), C32H40N2O18 (2), C30H55N5O5 (3) and C17H14N2O2 (4). Natural products database query showed that compounds 3 and 4 were possibly viscumamide and dehydrocyclopeptin, respectively, and compounds 1 and 2 were novel molecules. Viscumamide and dehydrocyclopeptin were detected from entomogenous fungi for the first time.

Key words:Isaria gracilioides, Ree radical scavenger, LC-HRMS, 1,1-Diphenyl-2-picryhydrazyl (DPPH)