Antigenotoxicity and antioxidant activities of bitter leaf (Vernonia amygdalina del.) accessions from different parts of Nigeria

Bitter leaf (Vernonia amygdalina Del.) plant is a tree species that is highly cultivated in Nigeria for its nutritive and therapeutic values. This study aimed to determine the antioxidant and antigenotoxicity effects (in vitro) of 52 accessions of V. amygdalina collected from six geopolitical zones of Nigeria (North East, North West, North Central, South South, East and West) by evaluating the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO-) scavenging antioxidant activities, flavonoid and phenolic contents as well as ethidium bromide-induced DNA (deoxyribonucleic acid) damage of bitter leaf. The results showed that accessions MN628016 (Oshimili South, Delta State) and MN628010 (Akoko Edo, Edo State), respectively had higher amounts of flavonoid (287.19 mg/g/FW) and phenolic (307.90 mg/g/FW) contents. The accessions MN627984 (Ikpoba Okha, Edo State) and MN627975 (Owerri, Imo State) had the highest nitric oxide (85.73%) and DPPH radical scavenging inhibitory effect (98.92%). The highest percentage fragmented DNA (45.05%), was observed in Allium cepa roots homogenised and mixed with ethidium bromide followed by the A. cepa roots homogenised and mixed with the leaf extract of V. amygdalina accession MN627977 (36.12%). However, V. amygdalina accessions MN628008 (457.62%, Warri North, Delta State) had the highest percentage increase of fragmented DNA followed by MN628024 (395.04%, Oshimili North, Delta State), MN628015 (345.54%; Aniocha North, Delta State) and MN627984 (342.04%; Ikpoba Okha, Edo State) while accession MN628010 (7.32%; Akoko Edo, Edo State) had the lowest. Accession MN628010 which possessed the highest amount of phenolic content had the lowest percentage increase of fragmented DNA and accession MN627984 which possessed the highest nitric oxide radical scavenging inhibitory effect was among the accessions with the highest percentage increase of fragmented DNA. The findings of this study suggest that the observed lowest percentage of fragmented DNA of A. cepa roots growth induced with the solution of ethidium bromide and treated with V. amygdalina accessions MN628010 extracts (antigenotoxic) could be as a result of the high antioxidant activities in the V. amygdalina accessions. In summary, the findings of this study showed that the 52 V. amygdalina accessions obtained from different locations of Nigeria will help to combat ethidium bromide induced genoxicities and any other genotoxicant that may lead to different complications in plant (A. cepa roots), as all the accessions possessed antioxidant and antigenotoxic properties, as such, possessed comparable amount of natural antioxidant activities and antigenotoxicity.