Main content area

Metabolism of Quercetin and Naringenin by Food-Grade Fungal Inoculum, Rhizopus azygosporus Yuan et Jong (ATCC 48108)

Gonzales, Gerard Bryan, Smagghe, Guy, Wittevrongel, Jens, Huynh, Nguyen Thai, Van Camp, John, Raes, Katleen
Journal of agricultural and food chemistry 2016 v.64 no.49 pp. 9263-9267
Rhizopus, beta-glucosidase, culture media, fermentation, fungi, glucosides, inoculum, metabolites, microbial culture, microbial growth, naringenin, quercetin, soybeans, starter cultures, sulfates, tempeh, toxicity
Rhizopus azygosporus Yuan et Jong (ATCC 48108), a starter culture for fermented soybean tempeh, produces β-glucosidases that cleave flavonoid glycosides into aglycones during fermentation. However, recent data suggest that fermentation of a flavonoid glycoside-rich extract with this strain did not result in the production of aglycones. Thus, in this paper, flavonoid metabolism of this strain was investigated. Incubation of flavonoid aglycones, naringenin and quercetin, with R. azygosporus resulted in the production of flavonoid glucosyl-, hydroxyl-, and sulfo-conjugated derivatives. Naringenin was completely metabolized within 96 h into eriodictyol sulfate and eriodictyol glucoside, whereas quercetin was partially metabolized into quercetin glucoside, diglucoside, sulfate, and glucosyl-sulfate. Most of these metabolites were found to be excreted by the fungi into the culture medium. Toxicity analysis revealed that incubation with both quercetin and naringenin did not exert inhibitory effects on fungal growth. This study presents an interesting mechanism of fungal detoxification of flavonoids in foods.