Antigenotoxic, antimutagenic and ROS scavenging activities of a Rhoeo discolor ethanolic crude extract.

Rhoeo discolor is a legendary plant used for treatment of superficial mycoses in Mexican traditional medicine. Despite its extended use, it is not known whether it has side-effects. An ethanolic crude extract from Rhoeo discolor was prepared, its mutagenic capacity was investigated by the Ames test, and its genotoxic activity in primary liver cell cultures using the unscheduled DNA synthesis assay. This extract was not mutagenic when tested with Salmonella typhimurium strains TA97, TA98 and TA100, and it did not elicit unscheduled DNA synthesis in hepatocyte cultures. In addition, we explored the antimutagenic and antigenotoxic activities of the extract and its ROS scavenger behaviour. Our results show that Rhoeo extract is antimutagenic for S. typhimurium strain TA102 pretreated with ROS-generating mutagen norfloxacin in the Ames test, and protects liver cell cultures against diethylnitrosamine induction of unscheduled DNA synthesis even at 1.9 ng per dish, which was the lowest dose tested. A free radical scavenging test was used in order to explore the antioxidant capacity of Rhoeo extract, as compared with three commercial well-known antioxidants quercetin, ascorbic acid and tocopherol. Rhoeo extract showed less radical scavenging effect than quercetin, but similar to that of alpha-tocopherol and more than ascorbic acid. It is important to note that this extract was neither mutagenic in S. typhimurium nor genotoxic in liver cell culture, even at concentrations as high as four- and 166-fold of those needed for maximal antimutagenic or chemoprotective activities, respectively.

Genotoxic and anti-genotoxic properties of Calendula officinalis extracts in rat liver cell cultures treated with diethylnitrosamine.

Calendula officinalis flower extracts are used to cure inflammatory and infectious diseases, for wound healing and even cancer with partial objective evidence of its therapeutic properties or toxic effects, many of which can be attributed to the presence of flavonols. We studied whether C. officinalis extracts induce unscheduled DNA synthesis (UDS) in rat liver cell cultures, and if these extracts can reverse diethylnitrosamine (DEN)-induced UDS. Four different flower extracts were prepared: aqueous (AE), aqueous-ethanol (AEE), ethanol (EE) and chloroform (CE). AE and AEE were evaporated to 6.72 and 4.54 mg of solid material per ml, respectively and final ethanol concentration in AEE was 0.8%. EE and CE were dried and resuspended in dimethyl sulfoxide (DMSO) to 19.2 and 10 mg of solid material per ml. Ethanol residue of EE was 0.34%. In the UDS assay in liver cell cultures, DEN at 1.25 microM produced a maximal increase of 40% (3)H-thymidine ((3)HdTT) incorporation, and both, AE and AEE showed complete reversion of the DEN effect at around 50 ng/ml and between 0.4 to 16 ng/ml, respectively. In the absence of DEN, these two polar extracts induced UDS at concentrations of 25 microg for AE and 3.7 microg/ml for AEE to 100 microg/ml in rat liver cell cultures. Concentrations producing genotoxic damage were three orders of magnitude above concentrations that conferred total protection against the DEN effect. Thus, at the lower end, ng/ml concentrations of the two polar extracts AE and AEE conferred total protection against the DEN effect and at the higher end, g/ml concentrations produced genotoxic effects. These results justify the study of C. officinalis flower extracts to obtain products with biological activity and to define their genotoxic or chemopreventive properties.