Total antioxidant potential of resinous exudates from Heliotropium species, and a comparison of the ABTS and DPPH methods

Total reactive antioxidant potential (TRAP) of resinous exudates from Helio tropium species was evaluated by measuring the bleaching of stable free rad icals. The antioxidant capacity of the resinous exudates in Trolox equivale nts, evaluated from the bleaching of ABTS derived radical cations, ranged f rom 2.0 M (H. huascoense) to 5.2 M (H. stenophyllum), indicating a very hig h concentration of phenolic compounds. Considerably smaller values were obt ained by measuring the bleaching of DPPH radicals. The ratio between the va lues obtained employing ABTS derived radicals and DPPH, ranged from 37 (H. megalanthum) to 4.5 (H. chenopodiaceum variety typica). The magnitude of th e difference can be considered as an indication of the relative reactivity of the antioxidants present in the exudates. Similar ratios were observed w hen stoichiometric coefficients were evaluated for representative purified flavonoids obtained from the resinous exudates.