THE BALANCE OF PLANT EXTRACTS POTENCY TO SCAVENGE MODEL RADICAL AND TO REDUCE FERRIC ION IN MODEL COMPLEX

Abstract

Fifty randomly selected plant extracts were evaluated for their ability to scavenge a model radical and to reduce ferric ions in a model complex, using the DPPH and FRAP assays applied simultaneously in a microplate format. The DPPH assay measures the capacity of extracts to scavenge the stable DPPH^• radical, broadly reflecting antioxidant potential. The FRAP assay assesses the ability to reduce Fe³⁺ in complex with TPTZ, which also indicates antioxidant activity but, under certain conditions, may reflect the potential to generate more reactive pro-oxidant metal ion species. The ratio of these two activities was expressed as the Pro-oxidant/Antioxidant Balance Index (PABI). Most extracts showed higher activity in the FRAP assay, suggesting a greater potential for potential pro-oxidant metal ion formation than radical scavenging. However, some taxa, including Aesculus hippocastanum L., Clematis vitalba L., Mespilus germanica L., and Piper nigrum L., displayed predominant radical scavenging activity. Both properties followed a normal distribution well-fitted by a Gaussian function, allowing extrapolation of frequency for chosen DPPH₅₀ and FRAP₅₀ values. Plant extracts with borderline PABI values, after systematic research, could be valuable for applications in the food industry, therapeutics, and cosmetics.