RESUMO
Clinical trials show an inverse relationship between the consumption of antioxidant-rich tree nuts and the development of chronic diseases. This study examined antioxidant efficacy of U.S. pecans using a modified cellular antioxidant activity (CAA) assay with comparisons to data from in vitro antioxidant assays (hydrophilic-oxygen radical absorbance capacity {H-ORACFL} and ferric reducing antioxidant power {FRAP}). Crude phenolic extracts from both raw and roasted pecans were analyzed. In the CAA assay, pecan phenolics were taken up by human colorectal adenocarcinoma (Caco-2) cells and bestowed CAA, determined by monitoring the fluorescence of 2',7'-dichlorofluorescein. Phenolics (25-100⯵g/mL) demonstrated a reduction in fluorescence by 37-69% for raw and 26-68% for roasted pecans. The primary active phenolic constituents were determined by high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) to be epi(catechin) dimers and trimers. These oligomeric procyanidins, ranging in size from 560 to 840â¯g/mol appear to be small enough for cellular uptake, showing pecans are an effective antioxidant in biological systems, regardless of roasting.
Assuntos
Antioxidantes/química , Carya/química , Células CACO-2 , Carya/metabolismo , Sobrevivência Celular/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Humanos , Nozes/química , Nozes/metabolismo , Fenóis/química , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
In vitro assays are widely used to analyze the antioxidant potential of compounds, but they cannot accurately predict antioxidant behavior in living systems. Cell-based assays, like the cellular antioxidant activity (CAA) assay, are gaining importance as they provide a biological perspective. When the CAA assay was employed to study phenolic antioxidants using hepatocarcinoma (HepG2) cells, quercetin showed antioxidant activity in HepG2 cells; 25 and 250µM quercetin reduced fluorescence by 17.1±0.9% and 58.6±2.4%, respectively. (+)-Catechin, a phenolic antioxidant present in many foods, bestowed virtually no CAA in HepG2 cells. When Caco-2 cells were employed, more robust antioxidant activity was observed; 50µM (+)-catechin and quercetin reduced fluorescence by 54.1±1.4% and 63.6±0.9%, respectively. Based on these results, likely due to differences in active membrane transport between the cell types, the Caco-2-based CAA assay appears to be a more appropriate method for the study of certain dietary phenolics.