Phenolic composition and antioxidant activities of cladodes of the two varieties of cactus pear (opuntia ficus-indica) grown in Ethiopia

Abstract

In this study, young cladodes corresponding to two (thorn-less and thorn-containing) varieties of cactus pear (Opuntia ficus-indica) from four different areas of Tigray region, Ethiopia, were investigated for their phenolic contents and antioxidant activities. Quantitative estimation of total phenolic contents and antioxidant activities in the cladodes was carried out using spectrophotometric methods. A 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay was used for the determination of the antioxidant activities, while Folin-Ciocalteau reagent, aluminum chloride and protein (albumin) precipitation methods were used for the determination of total polyphenol, flavonoid and tannin contents, respectively. The cladodes were found to be rich in polyphenols, with values in the range 18.0-71.4 mg gallic acid equivalent (GAE)/g of dry weight (DW). The predominant part of the polyphenols is represented by tannins, 9.00-41.2 mg GAE/g of DW, followed by flavonoids, 6.40-25.0 mg catchin equivalent (CE)/g of DW. The cladodes showed strong antioxidant activities, 59.3-85.8% inhibition compared to ascorbic acid. Application of paired t-test on the overall mean total polyphenol contents of samples collected from the different areas revealed the presence of significant variation between the thorn-less (31.6 GAE/g of DW) and thorn-containing (47.7 GAE/g of DW) varieties. One-way ANOVA also revealed that there are significant variations among samples from the same variety but collected from different areas.