Background: Black cumin seed contains considerable amounts of bioactive phenolics that have physiological activity and antioxidant potency, which may be boosted by microwave radiation. The core objective of the study was to evaluate the influence of microwave radiation on the antioxidant activity of cumin seed as a function of pretreatment time and extract concentration.
Methods: In this study, total flavonoid content (TFC) and antioxidant activity of methanol (CME), 70% methanol in water (CMW), ethanol (CEE) and 70% ethanol in water (CEW) extracts of microwaved radiated cumin seed were measured. The antioxidant activity was determined using a Folin-Ciocalteu assay, phosphomolybdenum assay, DPPH radical scavenging activity, H2O2 scavenging activity, hydroxyl radical scavenging activity and reducing power. To predict antioxidant potency, FTIR spectra of extracts were also recorded.
Results: Microwave pretreatment significantly reduced the TFC with the pretreatment time. Antioxidant activity increased with increasing pretreatment time and extract concentration in all extracts. Aqueous methanolic extract from radiated seeds appeared to display the highest effectiveness. The results from FT-IR of ex- tracts indicating the existence of multiple functional groups were comparable to those obtained from multiple antioxidative assays. The antioxidant effectiveness of the samples was ranked: CMW > CEW > CME > CEE.
Conclusions: Both treatment duration and extract concentration were found to be critical factors in determin- ing the overall quality of the product. The present study revealed important information for using black cumin seed in developing food products with high antioxidant potency.
Keywords: antioxidant activity; black cumin; microwave pretreatment; scavenging activity.