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. Key words: Hibisicus sabdariffa, roselle, antioxidant activity, flavonoids, phenolic content.
Highlights
Free radicals are unstable and highly reactive chemical species containing unpaired electrons in their atomic orbital (Lobo et al, 2010)
Total phenolic content (TPC) in the leaf samples ranged from 20 ± 0.6 (RNL) to 90 ± 0.6 μg/g (Sob-4)
Total phenolic contents observed in the current study were lower than values obtained in similar studies in ethanolic and aqueous extraction systems of roselle leaves in Brazil (Formagio et al, 2015) or elsewhere (Sirag et al, 2014; Al-Hashimi, 2012)
Summary
Free radicals are unstable and highly reactive chemical species containing unpaired electrons in their atomic orbital (Lobo et al, 2010) They occur either naturally in the human body as products of normal biochemical processes or are derived from the effects of ionizing radiation. L-1, L-2, L-4A, L-4B, L-5B, L-5A, L-5C, L-7, S-1, Sob-1, Sob-2, Sob-3, Sob-4, Sob-5, Sob-6, Sob-7,Sob, Sob-9, Sob-10, RNL, RBL , WH-S2, WHN-S2BL, WNL-HLS, WNL-VSH2, WHN-HS, WH-S2VLPro, WNL-STT, WNL-H, WNL-VSHT, WNL-HS, WBL, WH-S2V WH-S2TP, WH-S2VL Don-1, Don-2, Don-3, Don-4,N1-NL, N1-GP, N-3, N-4, N-5, S-2 body on important components such as carbohydrates, proteins, lipids and DNA This damaging effect can cause oxidative stress which leads to degenerative diseases such as atherosclerosis, cancers and diabetes (Oboh and Rocha, 2006; Young and Woodside, 2001; Bagchi et al, 2000) which account for about 1.7 million (2.8%) deaths worldwide (WHO, 2016). Important examples of antioxidants include polyphenols, lycopenes and flavonoids which can be obtained from fruits and vegetables (Karadag et al, 2009; Cai et al, 2004)
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