Effect of solvent polarity and extraction time on in vitro antioxidant properties of Brassica oleracea Convar Capitata Var L. seeds

Effect of solvent polarity and extraction time on antioxidant properties of Brassica oleracea seeds was optimized by response surface methodology using central composite design. A significant linear negative effect of solvent polarity on total extractable components (TEC), total phenolic acids (TPA), linoleic acid reduction capacity (LARC) and hydroxyl radical scavenging capacity (HRSC) and significant positive effect on iron chelating activity (ICA), reducing power (RP) and (DPPH RSC). Linear effect of solvent polarity on total antioxidant activity (TAOA) was also found to be positive but not significant. Significant linear negative effect of extraction time was observed on ICA and HRSC. Only RP was found to be significantly increased with increase in extraction time. Quadratic effect of solvent polarity was found to be negative on TAOA, DPPH RSC and HRSC. However, quadratic effects of both variables were found to be positive on TEC, TPA, ICA and LARC. The polarity dependent increase in TAOA indicates the extraction of phytochemicals with comparatively stronger antioxidant properties in polar solvents. The decrease in antioxidant properties in response to increase in extraction time may be attributed to the time dependent loss of antioxidant activity of extracted compounds.