Background – Polyphenols from different plant sources have been investigated for their antioxidant activities.
Polyphenols have been reported to exhibit anti-allergenic, anti-inflammatory and cardioprotective effects (1).
Objective – To compare the outcomes of in vitro and in vivo measures of antioxidant activity of palm polyphenols.
Design – In the in vitro experiments, human plasma was incubated with palm polyphenol extracts, and the antioxidant capacity was measured by two methods: 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical .+
cation (ABTS ) scavenging and ferric reducing antioxidant power (FRAP) assays. For the in vivo study, hamsters
were fed an atherogenic diet and supplemented with palm fruit juice (PFJ) for 8 wk. PFJ was administered at three
different polyphenol concentrations, 750, 1000, and 1500 mg gallic acid equivalents (GAE)/L. The antioxidant
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Outcomes – Incubation of human plasma with palm polyphenols did not result in a significant increase in plasma
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capacity of the hamster plasma was measured at the end of 8 wk by the ABTS
scavenging and FRAP assays. scavenging capacity, but plasma FRAP values were significantly elevated. A similar trend was observed in
ABTS
the in vivo experiments. ABTS scavenging capacity in hamster plasma was unaffected by PFJ treatment at the different PFJ concentrations administered. Plasma FRAP values, on the other hand, increased from 45.64 ± 24.96 μM Trolox equivalents (TE) in control animals given water, to 82.33 ± 41.26 μM TE in animals supplemented with PFJ at 1500 mg GAE/L.
Conclusions – In vitro measures of antioxidant capacity are useful indicators of possible outcomes of in vivo trials. Nevertheless, the quantitative outcomes of the latter may differ from what could be extrapolated from purely in vitro measures due to absorption, metabolism and bioavailability of ingested antioxidants.
Reference