Assessment of the Genotoxicity and Mutagenic Potential of Two Medicinal Plants, Parinari Curatellifolia (Planch. Ex Benth.) Kuntze and Azadirachta indica A. Juss, Using the Allium cepa Assay and the Ames Test

Abstract

In this study, two medicinal plants, Parinari curatellifolia (Planch. ex Benth.) Kuntze and Azadirachta indica (A. Juss) were collected in Sokode town, in Central Region of Togo. Their leaves and stem bark were screened for phytochemical composition, genotoxic and mutagenic potential. Qualitative analysis of the methanol and water extracts of both plants showed presence of saponins, tannins, glycosides, alkaloids, flavonoids, phytosterols and terpenoids. Azadirachta indica leaf registered the highest quantity of flavonoids at 25.46 % (g/100g) for the methanol extract and 23.87 % w/w for the aqueous extracts. Total phenols in Azadirachta indica leaf was 8.58 % w/w for the methanol extract and 7.33 % w/w in aqueous extracts. The amount of flavonoids in Parinari curatellifolia stem bark was 23.63 % w/w and 18.16 % w/w in the methanol and aqueous extracts respectively. Aqueous Parinari curatellifolia stem bark extract, had the highest concentration of alkaloids at 1.75 % w/w. which may be a cause of the high genotoxic activity in A. cepa. The Allium cepa assay was used to test the potential genotoxicity of the extracts from both plants. Four concentrations of each extract were used in the test: 0.125, 0.25, 0.5 and 1 g/l. The cytotoxic effects of the two plant extracts were evaluated regarding their ability to inhibit the root growth of onion seedlings. The EC50 values have shown that the extracts displayed an inhibitory property on the root growth of A. cepa seedlings. However, A. indica leaf aqueous extract was the most cytotoxic with an EC50 value of 0.26 g/l, followed by P. curatellifolia leaf methanol extract (EC50 = 0.46 g/l). The aqueous extract of P. curatellifolia stem barks and leaves exhibited a low cytotoxicity with EC50 values of 1.12 g/l each. The change in mitotic index was used to evaluate genotoxic potential of the extracts. After exposing Allium cepa cells to P. curatellifolia stem bark extracts, chromosomal bridges occurred at the concentrations of 0.5 g/l and 1 g/l of aqueous extract and 0.125 g/l, 0.5 g/l and 1 g/l of methanol extract. Chromosomal bridges were induced by Parinari curatellifolia leaves from 0.125 g/l to 1 g/l with both its aqueous methanol extracts. Treatment with aqueous leaf extract of Azadirachta indica resulted in the same type of aberration at 0.5 g/l and 1 g/ while the methanol extract caused bridges at 0.125 g/l, 0.5 g/l and 1 g/l. The c-mitosis was observed from 0.125 g/l to 1 g/l in Allium cepa cells treated with both aqueous and methanolic extracts of P. curatellifolia stem bark and leaves as well as A. indica leaves. Sticky anaphase was recorded from 0.25 g/l to 1 g/l in A. cepa cells treated with P. curatellifolia stem bark aqueous extract as well as at 0.25 g/l and 1 g/l of P. curatellifolia leaf methanol extracts. P. curatellifolia aqueous leaves did not cause sticky chromosomes. However, A. indica aqueous leaf extract caused sticky chromosomes at 0.5 g/l and 1 g/l while they were recorded at 0.25 g/l and 1 g/l after treatment with its methanolic extract. Bipolar anaphase was induced with 0.5 g/l and 1 g/l of P. curatellifolia stem bark and A. indica leaf methanolic extract. Chromosome fragments were observed at 0.5 g/l and 1 g/l after treatment with P. curatellifolia stem bark and A. indica methanolic extracts. Fragments occurred at 0.125 g/l to 1 g/l of P. curatellifolia leaf aqueous and methanol extracts, P. curatellifolia stem bark aqueous extract, at 0.5 g/l and 1 g/l of A. indica leaf methanolic extract and from 0.25 g/l to 1 g/l of A. indica leaf aqueous extract. The mutagenic assay was performed on Salmonella typhimurium TA 98 and TA 100 strains. The Ames test revealed a mutagenic activity in Azadirachta indica leaf from 0.0625 mg/ml for the aqueous extract with Salmonella typhimurium TA98 and TA100 without metabolic activation. The A. indica methanol leaf extract was mutagenic from 0.0625 mg/ml to 1 mg/ml with TA 98 and from 0.125 mg/ml to 1 mg/ml with TA 100 strain. Parinari curatellifolia leaf aqueous extract was mutagenic on Salmonella typhimurium TA 100 at 0.25 mg/ml, 0.5 mg/ml and 1 mg/ml but not mutagenic on TA 98 strain. However, the methanol extract of Parinari curatellifolia leaves was only mutagenic at 1 g/l for both Salmonella typhimurium TA 98 and TA 100. Parinari curatellifolia stem bark aqueous extract was mutagenic from 0.125 mg/ml to 1 mg/ml for both TA 98 and TA 100 while the methanolic extract was mutagenic at 0.25 mg/ml, 5 mg/ml and 1 mg/ml. Results of this study show that leaf and stem bark extracts from the two plants have genotoxic and mutagenic potential against Allium cepa and Salmonella typhimurium cells. They are therefore likely to have the same effects on human cells. Studies on mutagenic and genotoxic effects of these extracts on human cells should be done.