OPUNTIA FICUS-INDICA AND OPUNTIA MACRORHIZA: PROMISING SOURCES OF FLAVONOLS - COMPARISON BETWEEN CULTIVARS FROM DIFFERENT ORIGINS

Identification and quantification of flavonol glycosides in pulps and peels of Opuntia ficus-indica from different origins (Egypt, Sicily and South Africa) and Opuntia macrorhiza fruits were done using HPLC-DAD and HPLC-MS. In addition a gentle enzymatic hydrolysis of flavonol glycosides using commercial pectolytic enzymes was applied. Finally a comparison of antioxidant activities between all investigated matrices was carried out using electron paramagnetic resonance (EPR) spectroscopy. Results indicated that both, O. ficus-indica and O. macrorhiza, are characterized by high amounts of isorhamnetin glycosides (mainly isorhamnetin 3-O-rutinoside). O. ficus-indica showed the same profile of isorhamnetin glycosides in the peels of all origins. However, the isorhamnetins have not been detected in the pulps. In contrast, O. macrorhiza peels illustrated a different profile of isorhamnetin glycosides. The enzymatic hydrolysis of flavonol glycosides, produced only isorhamnetin as the only aglycon. Obtained results indicate that isorhamnetins could be considered as markers for the cactus pear fruits, or for adulteration of their processed products. Antioxidant activities of all investigated O. ficus-indica peels were higher than those of all pulps.