Rhamnosidase activity of selected probiotics and their ability to hydrolyse flavonoid rhamnoglucosides.

Bioavailability of flavonoids is low, especially when occurring as rhamnoglucosides. Thus, the hydrolysis of rutin, hesperidin, naringin and a mixture of narcissin and rutin (from Cyrtosperma johnstonii) by 14 selected probiotics was tested. All strains showed rhamnosidase activity as shown using 4-nitrophenyl α-L-rhamnopyranoside as a substrate. Hesperidin was hydrolysed by 8-27% after 4 and up to 80% after 10 days and narcissin to 14-56% after 4 and 25-97% after 10 days. Rutin was hardly hydrolysed with a conversion rate ranging from 0 to 5% after 10 days. In the presence of narcissin, the hydrolysis of rutin was increased indicating that narcissin acts as an inducer. The rhamnosidase activity as well as the ability to hydrolyse flavonoid rhamnoglucosides was highly strain specific. Naringin was not hydrolysed by rhamnosidase from probiotics, not even by the purified recombinant enzyme, only by fungal rhamnosidase. In conclusion, rhamnosidases from the tested probiotics are substrate specific cleaving hesperidin, narcissin and to a small extent rutin, but not naringin.