Studies on the antimutagenesis of Phyllanthus orbicularis: mechanisms involved against aromatic amines

Phyllanthus orbicularis is a medicinal plant, endemic to Cuba, whose aqueou s extract has proven antiviral properties. This plant extract is being stud ied for treatment of viral diseases in animals and humans. Antimutagenic ac tivities of this plant aqueous extract have been investigated as an additio nal and possible valuable property. Antimutagenesis was assayed against the mutagenic activity of m-phenylenediamine (m-PDA), 2-aminofluorene (2-AF), 1-aminopyrene (1-AP), 2-aminoanthracene (2-AA) and 9-aminophenantrene (9-AP ) in Salmonella typhimurium (S. typhimurium) YG1024, in different co-treatm ent approaches. This plant extract produced a significant decrease of the m utagenesis mediated by these aromatic amines (AA) in the following order: m -PDA > 2-AA > 2-AF > 9-AP > I-AP. Interactions with S9 enzymes and transfor mation of promutagenic amines and their mutagenic metabolites by chemical r eactions to non-mutagenic compounds are proposed as possible mechanisms of antimutagenesis. Mutagenesis mediated by m-PDA was almost completely abolis hed when S9 mixture was co-incubated with the plant extract during 40 min, previous to the addition of the m-PDA and bacterial cells to the assay. Sim ilar results were found with 2-AA and I-AP, but the reduction of the mutati on rate was not so dramatic. In contrast, the most significant antimutageni c effect against 2-AF and 9-AP was seen when these chemicals were co-incuba ted with the plant extract, before addition of the S9 mixture and bacterial cells to the assay. Therefore, inhibition or competition for S9 enzymes se ems to be the main antimutagenic mechanism of this plant extract against in -PDA, 2-AA and 1-AP, whilst a chemical modification of 2-AF and 9-AP into n on-promutagenic derivatives is likely to be the main mechanism of antimutag enesis against both compounds. (C) 2001 Elsevier Science B.V. All rights re served.