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Most studies on bioavailability of phenolic antioxidants are focused in foods and beverages in which they may be easily released from the food matrix, reaching a peak in plasma antioxidant capacity 1-2 h after the intake. However, plant foods contain significant amounts of polyphenols associated with dietary fiber. The aim of the present work was to seek the bioavailability of total phenolic antioxidants associated with dietary fiber by measuring plasma antioxidant capacity in human volunteers. An acute intake of 15 g of a dietary fiber rich in associated phenolic antioxidants in healthy volunteers (n = 10) increased antioxidant capacity of plasma in relation to a control group (n = 4), becoming significant 8 h after the intake. This shows that phenolic antioxidants associated with dietary fiber are at least partially bioavailable in humans, although dietary fiber appears to delay their absorption. No significant changes were observed after long-term intake (16 weeks, 34 subjects).

Summary Several tropical fruits have been described as natural sources of dietary fibre (DF) and phenolic compounds, associated with different health effects. The aim of this work was to ascertain the DF, phenolic compounds content (including non‐extractable polyphenols, mostly associated with DF) and antioxidant capacity in acerola fruits and cashew apples from selected clones. ‘BRS 236’ acerola fruits presented a high antioxidant capacity because of the combination of both extractable polyphenols and l‐ascorbic acid (providing together a Folin value of 170 kg−1 g d.m.). ‘CCP 76’ cashew apples contained 28 g kg−1 d.m. of extractable polyphenols and 13 g kg−1 d.m. of ascorbic acid as well as a high amount of non‐extractable condensed tannins (52 g kg−1 d.m.). DF content was of 260 g kg−1 d.m. in acerola fruit and of 209 g kg−1 d.m. in cashew apple. Acerola fruits and cashew apple should therefore be considered as new natural sources of DF and phenolic compounds.