Antioxidant, antimutagenic and antigenotoxic properties of Plectranthus species

Abstract

Dichlomethane (DCM) and 90% methanol of sixteen Plectranthus species were investigated for antioxidant activity using the DPPH (2, 2-diphenyl-1-picrylhydrazyl), ABTS (2, 2-azinobis (3-ethylbenzothiazoline 6-sulfonate)) and FRAP (ferric reducing antioxidant power) assays. The Plectranthus species were also investigated for antimutagenicity using the Ames assay and antigenotoxicity using the vitotox assay. Dichloromethane extracts of Plectranthus barbatus, P. neochilus and P. argentatus, as well as 90 % methanolic extracts of Plectranthus caninus, P. fruticosus james and P. argentatus had the highest antioxidant activity in the DPPH assay. DCM extracts of P. amboinicus, P. montanus P. neochilus and P. madagascariensis had moderate to strong antimutagenicity in the Ames test at the highest concentration tested. In the vitotox assay, dichloromethane extracts of P. caninus, P. neochilus, P. ernstii, P. verticillatus, P. madagascariensis, P. montanus and the 90 % methanol extract of P. verticillatus were cytotoxic at the highest concentration tested. Of the 32 plant extracts investigated in this study, 68% showed better antioxidant activity than ascorbic acid (vitamin C), particularly in the DPPH and ABTS assays. Additionally, most plant extracts investigated in this study had antimutagenic properties against aflatoxin B1- induced mutagenicity in either the Ames or vitotox assay, or both, without a clear trend or correlation between antioxidant activity and antimutagenic properties.