POLYPHENOLIC ANALYSIS AND ANTIOXIDANT PROPERTIES OF THE ETHIOPIAN SPICES, Foeniculum vulgare Mill. And Syzygium aromaticum (L.) Merr. & Perry

Abstract

Natural products, especially those of spices origin, have always been an important source of therapeutic agents against chronic oxidative stress-related diseases. This study was aimed to analyse polyphenolic metabolites and antioxidant activity of Ethiopian Clove or kirunfud (Syzygium aromaticum (L.) Merr.) and Fennel or ensilal (Foeniculum vulgare Mill.) extracts. Seeds of fennel and flower of clove were purchased and extraction was done using chloroform, ethyl acetate, methanol and water solvents in triplicate. Qualitative identification analysis of the obtained extracts was performed using standard procedure, and quantitative estimation of representative polyphonic content were determined using spectrophotometer technique at different UV light. Antioxidant capacity of extracts of the spices was determined using Dipenyl Picryl Hydrazyl (DPPH), nitric oxide, hydrogen peroxide scavenging and reducing power assays. The result showed that, the phenols and flavonoids were predominantly presented in more polar solvent extracts of fennel and clove. The aqueous extracts of both spices showed significantly the highest total phenolic compound. Methanolic fennel and aqueous clove extracts showed significantly higher total flavonoid content. Antioxidant activity tests showed that ethyl acetate fennel extracts showed the highest DPPH scavenging at all concentrations compared to the standard Butyl Hydroxy Toluene (BHT). Chloroform fennel extracts showed the highest NO- radical scavenging activity at all concentration compared to the BHT and other extracts, except at 400 μg/mL, and chloroform clove extracts showed the highest NO- radical scavenging activity at all concentration compared to the standard (BHT) and other extracts, except at 25 μg/mL. Among the fennel and clove spice solvent extracts, the potent H2O2 free radical scavenger was methanolic extract at all concentrations, except at 400 μg/mL for fennel and 25 μg/mL for clove. For fennel, the best reducing power was showed by ethyl acetate extract for clove, the best reducing power was showed by methanolic extract. The study showed that the extracts have the proton – donating ability and could serve as free radical inhibitors or scavengers, acting possibly as primary antioxidants. In vivo antioxidant activity and isolation of antioxidant components of the tested spices are recommended to be carried out.