Parthenin, a sesquiterpene lactone of Parthenium hysterophorus L. is a high toxicity clastogen.

The in vitro and in vivo genotoxicity of parthenin, a sesquiterpene lactone from Parthenium hysterophorus L. with allergenic and irritant action, was assessed in three short-term tests: bacterial reversion in Salmonella typhimurium and Escherichia coli, in vitro chromosomal aberrations in peripheral blood lymphocytes and micronuclei in mouse peripheral blood. Parthenin was not mutagenic in S. typhimurium strains TA 1535, TA 1537, TA 98 and TA 100 but a weak response was observed in TA 102 (+S9) from 0.19 to 1.22 micromole per plate. Concentrations of 7.62 micromole per plate or higher were toxic, but the effect was reduced when S9 was present. Screening of oxidative mutagenesis with E. coli strains IC 188 and IC 203 gave negative results. Parthenin induced chromosomal aberrations, mainly chromatid breaks, in blood lymphocytes exposed to 10-60 microM during 20 h. An association was found with cytotoxicity, since concomitant nuclear alterations such as pycnosis, micronuclei and karyorrhexis were observed. Sister chromatid exchanges (SCEs) in lymphocytes were not influenced by exposure to parthenin; rather a decrease was observed at 60 microM. On the other hand, a minor increment in polyploid metaphases was found at 40 microM. When a single intraperitoneal (i.p.) dose of 4-31 mg/kg of parthenin was administered to mice, a positive increase in the micronucleated reticulocyte (RET) frequency was observed at 48 h for both sexes at the highest dose.