Flavonoid content and antioxidant properties of some tropical and subtropical fruits from the Annonaceae and Citrus genera

We have investigated the composition and properties of some tropical and subtropical fruits belonging to the Annonaceae and Citrus genera. RP-HPLC-DAD-MS-MS analysis showed that cherimoya (A. cherimola) is characterized by the abundance of flavan-3-ols (epicatechin and procyanidins), kumquat (C. japonica) by a dihydrochalcone (phloretin-di-C-glucoside) and flavones, sweet lemon (C. limetta) by flavanones (neohesperidin and eriocitrin) and flavones, and citron (C. medica) by flavones (dosmetin-di-C-glucoside, neodiosmin) and flavanones. Cherimoya extracts possess remarkable radical scavenging ability towards DPPH•, ABTS•+, O2•– and OH•– (IC50 100–490 gallic acid equivalents), and they have been tested for their anti-peroxidation and cytoprotective effects on tertbutylhydroperoxide-treated cells, and for their ability to avoid protein and DNA degradation by HOCl and Fenton-type reactions. As for kumquat, crude juice, selected flavonoid fractions and the main dihydrochalcone component have been tested separatedly against DPPH• and ABTS•+, gaining insight on the constituents responsible for antoxidant activity.