Tumor promoter-like activity of the molluscicidal latex of 'Crown-of-Thorns' (Euphorbia milii var. hislopii) in the V79 metabolic cooperation assay.

The latex of 'Crown-of-Thorns' (Euphorbia milii var. hislopii, syn. E. splendens) has been shown to be a potent plant molluscicide that could be used against the snails which are intermediate hosts of Schistosoma trematodes. However, a comprehensive toxicological evaluation of the latex is necessary before its large-scale use in schistosomiasis control becomes possible. In fact, one cause for concern is the presence of tumor-promoting phorbol esters in several plants of the Euphorbiaceae family. Phorbol esters as well as a number of other known tumor promoters share the common property of inhibiting metabolic cooperation (i.e., exchange of low molecular weight molecules via gap junctions) between Chinese hamster V79 cells in monolayer cultures. The present study was undertaken to determine if latex of E. milii presents tumor promoter-like activity is this short-term in vitro assay. Samples of lyophilized E. milii latex were tested at a noncytotoxic concentration range (1, 10, 50 and 100 micrograms/ml) in three independent experiments. 12-O-Tetradecanoylphorbol-13-acetate (10 ng/ml) was used as positive control. In all three assays, E. milii latex consistently inhibited metabolic cooperation between V79 cells at concentrations > or = 10 micrograms/ml. These results that E. milii latex contains tumor-promoting substances. These findings suggest that the use of crude latex as a molluscicide may pose a carcinogenic hazard to people who are continuously exposed to the product.

Tumor promoter-like activity of the molluscicidal latex of 'Crown-of-Thorns' (Euphorbia milii var. hislopii) in the V79 metabolic cooperation assay

The latex of 'Crown-of-Thoms'(Euphorbia miliivar. hislopii, syn. E. splendens) has been shown to be a potent plant molluscicide that could be used against the snails which are intermediate hosts of Schistosoma trematodes. However, a comprehensive toxicological evaluation of the latex is necessary before its large-scale use in schistosomiasis control becomes possible. In fact, one cause for concern is the presence of tumor-promoting phorbol esters in several plants of the Euphorbiaceae family. Phorbol esters as well as a number of other known tumor promoters share the common property of inhibiting metabolic cooperation (i.e., exchange of low molecular weight molecules via gap junctions) between Chinese hamster V79 cells in monolayer cultures. The present study was undertaken to determine if latex of E. milii presents tumor promoter-like activity in this shortterm in vitro assay. Samples of lyophilized E. milii latex were tested at a noncytotoxic concentration range (1, 10, 50 and 100 mug/ml) in three independent experiments. 12-0-Tetradecanoylphorbol-13-acetate (10 ng/ml) was used as positive control. In all three assays, E. milii latex consistently inhibited metabolic cooperation between V79 cells at concentrations (10 mug/ml. These results indicate that E. milii latex contains tumor-promoting substances. These findings suggest that the use of crude latex as a molluscicide may pose a carcinogenic hazard to people who are continuously exposed to the product.

Evaluation of the mutagenicity of the molluscicidal latex of Christ's Crown (Euphorbia milii var. hislopii) in mammalian cells in vitro and in vivo.

The latex of Christ's Crown (Euphorbia milii var. hislopii, syn. E. splendens var. hislopii) is a highly active plant molluscicide and could be used for snail control to reduce the prevalence of schistosomiasis in endemic areas. In the course of its toxicological evaluation, the mutagenicity of the latex of Euphorbia milii was tested in mammalian cells in vitro and in vivo. Latex was investigated for its capability of inducing gene mutations and chromosome aberrations in V79 cells in the absence and presence of S9-mix. Concentrations up to 800 micrograms/ml neither induced gene mutations at the HPRT locus nor chromosome aberrations. Latex had no effect on the frequencies of chromosome aberrations in the bone marrow of male and female rats at a dose of 1000 mg/kg. The results indicate that latex of E. milii is not mutagenic in mammalian cells in vitro and in vivo and its use as a molluscicide does not pose a mutagenic hazard for humans.

Absence of genotoxic activity of beta-myrcene in the in vivo cytogenetic bone marrow assay.

beta-Myrcene (MYR, 7-methyl-3-methylene-1,6 octadiene) is a peripheral analgesic substance and one of the major constituents of lemongrass oil (Cymbopogon citratus, Stapf), a plant widely used in Brazilian folk medicine. In the present study the genotoxicity of MYR was evaluated in vivo using the rat bone marrow cytogenetic assay. Male and female Wistar rats weighing 250 g (223 to 286 g) and 178 g (168 to 186 g), respectively, were used. Two or four rats of either sex were treated orally with MYR (0.1, 0.5 and 1.0 g/kg po), corn oil (negative control) and cyclophosphamide 30 mg/kg ip (positive control). Animals were sacrificed and bone marrow cells were harvested 24 and 48 h after MYR administration. The mitotic index and the frequency of chromosome aberrations were evaluated. Fifty metaphase cells were examined per animal. A dose related increase in mitotic index was observed 24-h after MYR administration. No evidence of MYR-induced clastogenicity was observed under the experimental conditions of this in vivo assay. The present results and previous negative findings of in vitro mutagenicity tests strongly indicate that MYR is not a genotoxic substance.

Absence of genotoxic activity of beta-myrcene in the in vivo cytogenetic bone marrow assay

beta-Myrcene (MYR, 7-methyl-3-methylene-1,6 octadiene) is a peripheral analgesic substance and one of the major constituents of lemongrass oil (Cymbopogon citratus, Stapf), a plant widely used in Brazilian folk medicine. In the present study the genotoxicity of MYR was evaluated in vivo using the rat bone marrow cytogenetic assay. Male and female Wistar rats weighing 250 g (223 to 286 g) and 178 g (168 to 186 g), respectively, were used. Two or four rats of either sex were treated orally with MYR (0.1, 0.5 and 1.0 g/kg po), corn oil (negative control) and cyclophosphamide 30 mg/kg ip (positive control). Animals were sacrificed and bone marrow cells were harvested 24 and 48 h after MYR administration. The mitotic index and the frequency of chromosome aberrations were evaluated. Fifty metaphase cells were examined per animal. A dose related increase in mitotic index was observed 24-h after MYR administration. No evidence of MYR-induced clastogenicity was observed under the experimental conditions of this in vivo assay. The present results and previous negative findings of in vitro mutagenicity tests strongly indicate that MYR is not a genotoxic substance

Influence of beta-myrcene on sister-chromatid exchanges induced by mutagens in V79 and HTC cells.

The influence of beta-myrcene (MC) on sister-chromatid exchanges (SCE) in V79 cells induced by 4 S9 mix-activated indirect mutagens was studied. The mutagens used were cyclophosphamide (CP), benzo[a]pyrene (BP), aflatoxin B1 (AFB) and 9,10-dimethyl-1,2-benz[a]anthracene (DMBA). MC effectively inhibited SCEs induced by CP and AFB in a dose-dependent manner, but it had no effect on SCE induction by BP and DMBA. MC also reduced CP-induced SCE frequencies in a hepatic tumor cell line (HTC). These cells are metabolically competent and activate CP into its biologically active metabolites. Our results support the suggestion that MC modulates the genotoxicity of indirect-acting mutagens by inhibiting certain forms of the cytochrome P-450 enzymes required for activation of premutagens like CP and AFB.

Evaluation of the mutagenicity of beta-myrcene in mammalian cells in vitro.

The genotoxicity of the terpene beta-myrcene was evaluated in mammalian cells in vitro. Myrcene is the major constituent of oil of bay and hop which are used in the manufacture of alcoholic beverages. Myrcene is also present in lemon grass (Cymbopogon citratus), a plant widely used in Brazilian folk medicine. Recently, it was shown that myrcene is a very potent analgesic substance and might be an alternative to the already available analgesic drugs. Myrcene was tested up to 1,000 micrograms/ml (limit of solubility) in the presence and absence of S9-mix and did not induce chromosome aberrations and sister chromatid exchanges (SCEs) in human lymphocytes in vitro. Neither the mitotic index nor the proliferation index was influenced by the myrcene treatment. Myrcene did not cause increased mutation frequencies at the hprt-locus in V79-cells. Tests with and without S9-mix revealed negative results. There was no indication for induced cytotoxicity. However, myrcene reduced the SCE-inducing effect of cyclophosphamide in human lymphocytes in a dose dependent manner and also reduced the toxic and mutagenic effect of cyclophosphamide in V79-cells. Under the same test conditions, SCE induction by ethyl methanesulfonate (EMS) and benzo [a]pyrene (BP) was not significantly influenced by simultaneous myrcene treatment. The in vitro results show that myrcene is not mutagenic in mammalian cells, but has antimutagenic properties. The possibility that myrcene exerts its antimutagenic activity by inhibiting certain forms of the cytochrome P-450 isoenzymes required for activation of premutagens and precarcinogenes is discussed.