Oskar Schimmer

Aristolochic acid is a direct mutagen in Salmonella typhimurium

Extracts from plants used to be a major source of medicins. Although little information on the potential risk to health is available such extracts are still widely used in human therapy. Aristolochic acid (Fig. 1) is a natural plant product found in certain species of Aristolochiaceae. Extracts from the leaves and roots of Aristolochia clematitis L. have been recommended for the therapy of arthritis, rheumatism and festering wounds. Moreover, several species of Aristolochiaceae are active against bacteria and fungi. Further investigations [1, 2] have indicated that aristolochic acid increases phagocytosis in leukocytes of rabbits, guinea pigs and rats and influences the defence mechanism against Herpes simplex infections of rabbit eyes [3]. Toxicological studies have shown that aristolochic acid has a carcinogenic effect on rats [4]. A dose of 10 mg/kg/day over 3 months led to papillomatosis of the stomach with malign neoplasms. Within a period of 4 months after treatment multiple carcinomas were found in the stomach and in other tissues such as liver, kidney, bladder, lung and skin. In 1981 as a result of these data, the German Federal Health Office withdrew the licence of products containing aristolochic acid. We have used the method of Ames et al. [5] to determine the mutagenicity of aftstolochic acid (EGA-Chemie, D-7924 Steinheim). The experiments were performed with the Salmonella strains TA1535, TA100, TA1537, TA1538 and TA98 (about

The mutagenic potencies of plant extracts containing quercetin in Salmonella typhimurium TA98 and TA100

Four commercial ethanolic plant extracts, Tinctura Alchemillae, Extractum Crataegi, Extractum Myrtilli and Tinctura Hyperici, were tested for their mutagenicity in Salmonella typhimurium TA98 and TA100 with and without S9 mix obtained from rats pretreated with phenobarbital. The extracts studied differed greatly in their mutagenic potencies but exhibited a very similar mutation pattern in which the strongest effect was always seen in tester strain TA98 with S9 mix. Simultaneously we investigated the extracts for the presence of quercetin and kaempferol. Only quercetin was detected in small amounts by thin-layer chromatography (TLC). The fractions containing quercetin were separated and collected using a Sephadex LH-20 column. Two different methods were employed to estimate the amount of quercetin in the extracts: a colorimetric assay developed by Christ and Müller, and a complexometric method by Belikov. The quercetin concentrations ranged between 2 mg (Tinctura Alchemilla) and 89 mg (Tinctura Hyperici) per 100 g of extract. We suggest that the mutagenicity of the 4 plant extracts is mainly due to the presence of quercetin for the following reasons: (1) all the plant extracts exhibit a mutation pattern which is very similar to that of quercetin, (2) the mutagenic potential of the extracts correlates well with their quercetin content, considering the fact that plant extracts are very complex mixtures often containing toxic or antimutagenic compounds.

Induction of sister-chromatid exchanges (SCE), polyploidy, and micronuclei by plant flavonoids in human lymphocyte cultures. A comparative study of 19 flavonoids

Nineteen naturally occurring flavonoids were studied with regard to their SCE-inducing potency and their capability of inducing polyploidy and micronuclei in human lymphocyte cultures. The cells were treated for a period of 48 h. The flavone C-glycosides, vitexin and orientin, exhibited a moderate SCE-inducing activity, whereas the other compounds displayed only weak effects or were inactive. Polyploidy was induced by procyanidins consisting of 3 or 4 flavanol units and to a lesser extent by flavone, flavonol, and anthocyanidin aglycones. The aglycones as well as the C-glycosides and the O-glycosides, spiraeoside and luteolin-7-glucoside, were more or less active in inducing micronuclei in the lymphocytes. The flavonol O-glycosides, rutin and hyperoside, and the monomeric and dimeric flavanols failed to produce any genotoxic effects. The results are discussed with respect to a possible structure-activity relationship.

Induction of structural chromosome aberrations and sister chromatid exchanges in human lymphocytes in vitro by aristolochic acid

SummaryThe medicinal use of Aristolochia clematitis has been known for some time. The main active agent of this medicinal plant is aristolochic acid, a nitrophenanthrenecarbonic acid. Very recently, however, the Federal Health Office withdrew the licence for all drugs containing aristolochic acid, because of the well-founded suspicion that aristolochic acid may be a very potent carcinogen.We investigated the induction of structural chromosome aberrations and sister chromatid exchanges (SCEs) by aristolochic acid in human lymphocytes in vitro. Cells were treated with the agent tested throughout culture time and during the G0 phase of the cell cycle. We tested concentrations over a range of 1 to 20 μg/ml. Both treatment conditions resulted in an increased aberration frequency. The induction of gaps and breaks as well as the induction of SCEs showed a dose-dependent increase. The number of SCEs per metaphase was enhanced by a factor of 2 to 3. If conventional cytogenetic methods had been applied in time, one would have recognized the mutagenic risk of aristolochic acid earlier.

Mutagenicity and structure-mutagenicity relationships of furoquinolines, naturally occurring alkaloids of the Rutaceae

We report on the mutagenicity results of 6 further natural furoquinolines; additionally the mutagenic potency of in total 11 alkaloids with regard to their substitution pattern is compared

Mutagenic compounds in an extract from Rutae Herba (Ruta graveolens L.). II. UV-A mediated mutagenicity in the green alga Chlamydomonas reinhardtii by furoquinoline alkaloids and furocoumarins present in a commercial tincture from Rutae Herba.

A commercial tincture prepared from Rutae Herba (Ruta graveolens L.) exhibited a moderate photomutagenicity in an arginine-requiring mutant strain of Chlamydomonas reinhardtii. In the tincture some furocoumarins, e.g., bergapten, psoralen, imperatorin, and 3 furoquinoline alkaloids (dictamnine, gamma-fagarine, skimmianine) were detected. All compounds revealed photomutagenic properties but their activities were quite different. Bergapten was the most potent furocoumarin. Dictamnine, the furoquinoline with the strongest effect, reached only about 10% of the activity of bergapten. Based on the amount of these compounds in the tincture and their activities we conclude that bergapten is mainly responsible for the photomutagenicity of the tincture. The lower phototoxicity and photomutagenicity of the furoquinoline alkaloids may be due to the fact that furoquinolines form only monoadducts with DNA in the presence of UV-A in contrast to furocoumarins which also form biadducts.

Furoquinoline alkaloids as photosensitizers in Chlamydomonas reinhardtii

Seven naturally occurring furoquinoline alkaloids were investigated for their photobiological activity using arg-1 cells of Chlamydomonas reinhardtii. UV-A-mediated toxicity of the compounds was calculated from the colony-forming ability of the treated cells. The UV-A-mediated mutagenicity was measured by counting the number of Arg+ revertants induced by the treatment. Dictamnine was found to be the strongest mutagen as well as the most toxic compound of the group. The mutagenic activities were measured as mutation frequencies at equal substance concentration and ranked in the following order: An increase in the number of substituents on the lateral aromatic nucleus greatly decreased the photomutagenicity. Except for evolitrine, a similar ranking order was found as reported for the dark mutagenicity of these compounds in Salmonella typhimurium strain TA98. Based on the result that furoquinolines are able to intercalate into DNA, we assume that the different mutagenic potencies may reflect differences in the geometry of the intercalation complex, which is important for the subsequent photochemical reaction.

Vergleich der photomutagenen wirkungen von 5-MOP (Bergapten) und 8-MOP (Xanthotoxin) in Chlamydomonas reinhardii

Abstract Comparison of photomutagenic activities of 5-MOP (bergapten) and 8-MOP (xanthotoxin) in Chlamydomonas reinhardii The photomutagenic and phototoxic activities of 5-MOP and 8-MOP were compared in arg− cells of Chlamydomonas reinhardii and their ability to revert to Arg+ mutants. We determined the dependency of induction of Arg+ revertants from cell density, substance concentrations, UV-A fluence, and UV-A radiation intensities. Both furocoumarins were also tested for photomutagenicity under white-light conditions. In all experiments, 5-MOP was more active than 8-MOP. Only on the basis of saturation did both compounds show similarly strong mutagenic activities. When compared on the basis of equivalent cytotoxicity, the difference between the activities of 5-MOP and 8-MOP was smaller. The difference between the activities of the 2 compounds was higher when white light was used instead of UV-A. We could not find any strong reciprocity between substance concentration and UV-A fluence or between UV-A fluence and radiation intensity. We believe that the difference between the photomutagenic activities of 5-MOP and 8-MOP in Chlamydomonas reinhardii is caused by their different abilities to form intercalation complexes with DNA which thus determine the kinetics of the following photochemical reactions. In addition, the results presented here suggest that the mutagenic and cancerogenic potency of 5-MOP is similar to or even stronger than that of 8-MOP. The cancerogenic risk of both compounds may be markedly diminished by reducing the UV-A radiation intensities during photochemotherapy.

Volatile constituents of the essential oil of Grindelia robusta Nutt. and Grindelia squarrosa Dun

ABSTRACT The essential oils of Grindelia robusta and Grindelia squarrosa were analyzed by GC. The oil of G. robusta was found to contain 141 constituents of which 12 were identified. Bornyl acetate (12.28%) and α-pinene (12.15%) were the major compounds of the monoterpene fraction. The oil of G. squarrosa contained about 100 constituents and showed a very similar composition. α-Pinene (25.53%) was found to be a major compound

Effect of re-irradiation with UV-A on inactivation and mutation induction in arg− cells of Chlamydomonas reinhardii pretreated with furocoumarins plus UV-A

Abstract A re-irradiation period of 60 min with UV-A following pretreatment with 5′-methylangelicinlus UV-A induces only a slight increase in the inactivation of arg − cells. After pretreatment of arg − cells with 5-MOP plus UV-A and 8-MOP plus UV-A, respectively, a re-irradiation period of 30 min considerably increases the number of inactivated cells. However, after prettreatment with the monofunctional 5′-methylangelincin, as well as after pretreatment with either of the bifunctional furocoumarin derivatives, the slopes of the inactivation curves are changed at the beginning of the re-irradiation period. In contrast, mutation induction curves are not changed during a re-irradiation period of 30 min after pretreatment with 5-MOP and 8-MOP plus UV-A. The slopes of the curves are similar for both treatment conditions. The increase of the mutation frequencies during re-irradiation, however, is different: the mutation frequency is increased by a factor of 3–4 for 5-MOP and by a factor of 2 for 8-MOP within a re-irradiation period of 30 min. Based on these results, we conclude that mono-adduct formation does not seem to be significantly involved in mutation induction by functional furocoumarins plus UV-A in Chlamydomonas reinhardii .