Influence of cultivar and origin on the flavonol profile of fruits and cladodes from cactus Opuntia ficus-indica.

Flavonols are hypothesized to be the most important polyphenolic antioxidants. This present study aimed at investigating flavonols in cactus Opuntia ficus-indica fruits from two Egyptian cultivars in comparison to three common Sicilian cultivars, and two further cultivars from South Africa. Besides, cactus O. ficus-indica cladodes from Egyptian cultivars have been investigated as well. HPLC-DAD analyses showed that cactus O. ficus-indica fruits and cladodes are mainly characterized by isorhamnetin glycosides. These flavonols were found only in the fruit's peel and the cladodes, but not in the pulp. However, all analyzed cultivars exhibited the same flavonol profile which might therefore serve as a chemical fingerprint with regard to genuineness of cactus O. ficus-indica fruits and cladodes or even food products containing whole cactus fruits as ingredients. The findings obtained have been confirmed both by enzymatic hydrolysis of flavonol glycosides following analysis of the aglycons and by HPLC-ESI-MS. The concentration of total flavonols ranged from 2.2 to 4.1 and 6.3 to 7.6mg/g (dw) in the fruit peels and the cladodes, respectively. Further, fruit peels and cladodes exhibited high total phenolic contents and antioxidant activities compared to those of the fruit pulps. These investigations valorize cactus fruit's peel and cladode in comparison to fruit's pulp, and may further provide additional data for using flavonols in chemotaxonomic studies of cactus Opuntia spp. and authenticity of cactus O. ficus-indica products.