Radical-Scavenging Activities of Cactus Cladodes (Opuntia HumifusaRaf.) in a Submerged Culture

The aim of this work was to select suitable fermentation treatments for the efficient bioconversion of cactus bioactive components with an improved radical-scavenging activity for use as a nutraceutical. To obtain microorganisms for the microbial conversion of cactus, various fungi including Monascus pilosusKCCM 60029 (ATCC 22080) were used for the fermentation of cactus. DPPH (2,2-diphenyl-2-picrylhydrazyl hydrate) and ABTS [2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt] radical-scavenging activities in M.pilosus fermentation were enhanced by 70 and 50%, respectively, compared with control. In particular, uronic acid levels showed a remarkable increase (approximately over threefold) in fermentation. The polyphenol and quercetin content of the fermented cactus showed a large increase from 180 and 2μg/mL to 233.4 and 8.5μg/mL, respectively, showing a maximum level at 4 days of fermentation. This result correlated with the increase of the radical-scavenging activity, meaning that polyphenol and quercetin contents are associated with radical-scavenging activity. M.pilosus is a very useful tool in the fermentation of cactus and enhancement of radical-scavenging activity. Practical Applications: We adopted fungi-mediated fermentation for bioconversion of bioactive compounds with the improvement of radical-scavenging activity in Opuntia cladodes. Our study suggests that Monascus pilosus-mediated fermentation could be used for desirable modification of edible plant-derived components. This biochemical process would be applied as a way to convert compositions of various components in food substrates, including enhancement of bioactive components, in the food industry. Thus, our study would give useful information in the utility of microbial fermentation for biochemical conversion of food-derived bioactive components.