Phenolic compounds and biological properties of Burkina onions

Three onion cultivars from Burkina Faso were studied for their total phenol content and antioxidant activity according to the type of extraction the extraction solvent and the drying method. The total phenol content was determined by the Folin-Ciocalteu method and the antioxidant activity was measured by three methods: 22 - Diphenyl - 1 - picrylhydrazyl (DPPH) Ferric Reducing Antioxidant Power (FRAP) and 22'' - azino - bis (3 ethylbenz-thiazoline - 6 - sulfonic acid) (ABTS). The results show that the ethyl acetate macerated extracts of alize showed the best contents but respectively the shade dried onions (13.216 mg GSE/g dry extract) followed by the solar dried (3.883 mg GSE/g dry extract) and finally the fresh bulbs (3.402 mg GSE/g dry extract). The extracts from the shade-dried onions also showed the best antioxidant activities especially with the trade wind extract using the DPPH test (36.834 mg TE/g dry extract). This study shows that dried onion bulbs are a good source of natural antioxidants.