Screening for total antioxidant activity, flavonoids and phenolics variability in forty-five accessions of roselle (Hibiscus sabdariffa L.)

Abstract

Build-up of free radicals in the human body can cause oxidative stress which may invariably lead to degenerative diseases and eventual death. Antioxidants such as polyphenols and flavonoids found in fruits and vegetables have been shown to protect the body against the damaging effects of these free radicals. Roselle contains high amounts of antioxidants and its leaves are often used for sauces or in herbal preparations to treat certain ailments. Several landraces of roselle occur in Ghana but have not been screened for antioxidant activity. Leaf samples of roselle acessions were harvested 60 days after sowing, freeze dried and analysed for total phenolic content (TPC), total flavonoid content (TFC) as well as total antioxidant activity (TAA) using UV-VIS Spectrophotometer (Shimadzu, 1201, Japan). No statistically significant differences were observed in TPC which ranged from 20 ± 0.6 µg/g (RNL) to 90 ± 0.6 µg/g (Sob-4). TFC and TAA in the leaf samples; however, showed statistically significant variation and ranged from 10.04 ± 0.31 µg/g (WH-S2V) to 49.79 ± 0.48 µg/g (Don-1) and 37.48% (Don-4) to 58.58% (WNL-HS), respectively. Higher leaf phenolic or flavonoid content did not necessarily translate into a higher antioxidant activity. This suggests that other forms of antioxidants other than phenolics or flavonoids might be responsible free radical scavenging activity in roselle leaves. Nevertheless, very high free radical percentage inhibition observed in the roselle leaves makes it an excellent material for mitigation against the adverse effect of free radicals. Nine promising accessions with high free radical scavenging activity have been identified for further improvement.