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

Mutagenic potential of medicinal plants evaluated by the Ames Salmonella/microsome assay: A systematic review

The Ames test has become one of the most commonly used tests to assess the mutagenic potential of medicinal plants since they have several biological activities and thus have been used in traditional medicine and in the pharmaceutical industry as a source of raw materials. Accordingly, this review aims to report previous use of the Ames test to evaluate the mutagenic potential of medicinal plants. A database was constructed by curating literature identified by a search on the electronic databases Medline (via Pubmed), Science Direct, Scopus, and Web of Science from 1975 to April 2020, using the following terms: "genotoxicity tests" OR "mutagenicity tests" OR "Ames test" AND "medicinal plants." From the research, 239 articles were selected, including studies of 478 species distributed across 111 botanical families, with Fabaceae, Asteraceae and Lamiaceae being the most frequent. It was identified that 388 species were non-mutagenic. Of these, 21% (83/388) showed antimutagenic potential, most notable in the Lamiaceae family. The results also indicate that 18% (90/478) of the species were mutagenic, of which 54% were mutagenic in the presence and absence of S9. Strains TA98 and TA100 showed a sensitivity of 93% in detecting plant extracts with mutagenic potential. However, the reliability of many reviewed studies regarding the botanical extracts may be questioned due to technical issues, such as testing being performed only in the presence or absence of S9, use of maximum doses below 5 mg/plate and lack of information on the cytotoxicity of tested doses. These methodological aspects additionally demonstrated that a discussion about the doses used in research on mixtures, such as the ones assessed with botanical extracts and the most sensitive strains employed to detect the mutagenic potential, should be included in a possible update of the guidelines designed by the regulatory agencies.

Insights into the Phytochemistry of the Cuban Endemic Medicinal Plant Phyllanthus orbicularis: Fideloside, a Novel Bioactive 8-C-glycosyl 2,3-Dihydroflavonol

Phyllanthus orbicularis (Phyllanthaceae) is an endemic evergreen tropical plant of Cuba that grows in the western part of the island and is used in traditional medicine as an infusion. The aqueous extract of this plant presents a wide range of pharmacological activitiessuch as antimutagenic, antioxidant and antiviral effects. Given the many beneficial effects and the great interest in the development of new pharmacological products from natural sources, the aim of this work was to investigate the phytochemistry of this species and to elucidate the structure of the main bioactive principles. Besides the presence of several known polyphenols, the major constituent was hitherto not described. The chemical structure of this compound, here named Fideloside, was elucidated by means of HR-ESIMS/MSn, 1D/2D NMR, FT-IR, and ECD as (2R,3R)-(-)-3',4',5,7-tetrahydroxydihydroflavonol-8-C-β-D-glucopyranoside. The compound, as well as the plant aqueous preparations, showed promising bioactive properties, i.e., anti-inflammatory capacity in human explanted monocytes, corroborating future pharmacological use for this new natural C-glycosyl flavanonol.

The mutagenic and antimutagenic activity of Sutherlandia frutescens extracts and marker compounds

BACKGROUND

Sutherlandia frutescens (L.) R. Br is endemic to Southern Africa where it has been traditionally used for cancer and diabetes. In recent times it has been marketed for its reputed (but not proven) anticancer, antidiabetic and anti-HIV properties. Little is known about the mutagenic and antimutagenic potential of extracts and common marker compounds of Sutherlandia frutescens. Therefore this study aimed to investigate the putative efficacy and possible long-term adverse effects of using this herb.

METHODS

Ethylacetate (EA) and 50% Methanol (MeOH) extracts were screened for mutagenic and antimutagenic activity using the Ames assay utilising TA97a, TA98, TA100 and TA102 in the presence and absence of metabolic activation. Four compounds, L-arginine, L-canavanine, GABA and D-pinitol known to occur in sutherlandia were also included. The total polyphenolic content of the both extracts was determined using the Folin-Ciocalteau method and FRAP and ABTS were used to determine the anti-oxidant potential of the extracts.

RESULTS

The extracts and the standards did not show any cytotoxicity except in TA97a. The EA extract exhibited antimutagenicity against all the bacterial strains at all concentrations tested. The MeOH extract showed both pro-mutagenic and antimutagenic activities with 2-acetamidofluorene and aflatoxin B1 in the presence of metabolic activation of TA98 and TA100, respectively. All compounds, except L-canavanine exhibited antimutagenic activity against all strains. L-canavanine, on the other hand showed co-mutagenicity with 9-aminoacridine on TA97a, at all test concentrations. The extracts and pure compounds exhibited their antimutagenic activity in a dose response manner. L-arginine and GABA showed an some antimutagenic response. EA extract had three times the total phenolic content (12.56 μg GE / mg) observed in the MeOH extract. There was correlation between total phenolic content, antioxidant potential and antimutagenicity.

CONCLUSION

Both extracts exhibited a protective effect, with the EA extract exhibiting greater potency. L-canavanine acted as a co-mutagen in a dose response manner without metabolic activation. It is suggested that the EA extract be priotized for future development work as it showed a better risk profile and activity.

Anti-genotoxicity and anti-mutagenicity of Apis mellifera venom

The search for substances able to inhibit and/or diminish the effects of genotoxic and mutagenic substances has been the target of several investigations performed in recent times. Hymenoptera venoms constitute a considerable source of substances with pharmacological potential. The present study aimed to evaluate the cytotoxic, genotoxic and anti-genotoxic, mutagenic and anti-mutagenic potentials of Apis mellifera venom in HepG2 cells. In this evaluation, the MTT test was applied to determine the most appropriate concentrations for the genotoxicity and mutagenicity tests. It was verified that the concentrations of 0.1, 0.05 and 0.01μg/mL were not cytotoxic, hence these concentrations were used in the experiments. For the evaluation of the genotoxic and mutagenic potential of the bee venom the comet assay and the micronucleus test were applied, respectively. The concentrations mentioned above presented both genotoxic and mutagenic potential for HepG2 cells and it was necessary to test lower concentrations of the venom (10pg/mL, 1pg/mL and 0.1pg/mL) for the anti-genotoxicity and anti-mutagenicity tests, which were performed subjecting the cells to the action of MMS (methyl methanesulfonate) in order to verify the ability of the venom to inhibit or diminish the action of this compound, which has a recognized action on the genetic material. Pre-, post-treatment and simultaneous treatment with and without incubation with the venom were performed. It was observed that the lowest three concentrations tested did not present any anti-genotoxic and anti-mutagenic activity on the cells. The use of bee venom for pharmacological purposes in treatments such as cancer must be done with extreme caution, since it was observed that even at very low concentrations the venom can induce genotoxicity and mutagenicity in human cells, as was verified for the HepG2 cells.

Protective effect of a Phyllanthus orbicularis aqueous extract against UVB light in human cells

CONTEXT

One approach to protect human skin against the dangerous effects of solar ultraviolet (UV) irradiation is the use of natural products, such as photoprotectors. Phyllanthus orbicularis Kunth (Euphorbiaceae) is a Cuban endemic plant used in popular medicine. Its antigenotoxicity effect against some harmful agents has been investigated. However, the effect in ultraviolet B (UVB)-irradiated human cells has not been previously assessed.

OBJECTIVE

The protective effect of a P. orbicularis extract against UVB light-induced damage in human cells was evaluated.

MATERIALS AND METHODS

DNA repair proficient (MRC5-SV) and deficient (XP4PA, complementation group XPC) cell-lines were used. Damaging effects of UVB light were evaluated by clonogenic assay and apoptosis induction by flow cytometry techniques. The extent of DNA repair itself was determined by the removal of cyclobutane pyrimidine dimers (CPDs). The CPDs were detected and quantified by slot-blot assay.

RESULTS

Treatment of UVB-irradiated MRC5-SV cells with P. orbicularis extract increased the percentage of colony-forming cells from 36.03 ± 3.59 and 4.42 ± 1.45 to 53.14 ± 8.8 and 14.52 ± 1.97, for 400 and 600 J/m(2), respectively. A decrease in apoptotic cell population was observed in cells maintained within the extract. The P. orbicularis extract enhanced the removal of CPD from genomic DNA. The CPDs remaining were found to be about 27.7 and 1.1%, while with plant extract, treatment these values decreased to 16.1 and 0.2%, for 3 and 24 h, respectively.

DISCUSSION AND CONCLUSION

P. orbicularis aqueous extract protects human cells against UVB damage. This protective effect is through the modulation of DNA repair effectiveness.

In vitro toxicological properties of thymoquinone

Nigella sativa has been traditionally used for the treatment of inflammations, liver disorders, and arthritis. Experimentally, it has been demonstrated that N. sativa extracts and the main constituent of their volatile oil, thymoquinone, possess antioxidant, anti-inflammatory and hepato-protective properties. To further evaluate the toxicological properties in a metabolically competent cellular system, thymoquinone was applied to primary rat hepatocyte cultures, and both cyto- and genotoxic effects were tested. Mitotic indices and the rates of apoptoses and necroses were determined as endpoints of cytotoxicity, while chromosomal aberrations and micronucleated cells served as endpoints of genotoxicity. In this approach thymoquinone demonstrated cyto- and genotoxic effects in a concentration dependent manner: it induced significant anti-proliferative effects at 20 microM and acute cytotoxicity at higher concentrations. Thymoquinone significantly increased the rates of necrotic cells at concentrations between 2.5 and 20 microM. Furthermore, it induced significant genotoxicity at concentrations > or =1.25 microM. These observations support the previous finding that thymoquinone causes glutathione depletion and liver damage, but contradict the reports indicating antioxidant and anti-clastogenic effects. Thymoquinone might be metabolised to reactive species and increase oxidative stress, which contributes to the depletion of antioxidant enzymes and damage to DNA in hepatocytes treated with high thymoquinone concentrations.

Antimutagenic effect of essential oil of sage (Salvia officinalis L.) and its monoterpenes against UV-induced mutations in Escherichia coli and Saccharomyces cerevisiae

Mutagenic and antimutagenic potential of essential oil (EO) of cultivated sage (S. officinalis L.) and its monoterpenes: thujone, 1,8-cineole, camphor and limonene against UVC-induced mutations was studied with Salmonella/microsome, E. coli WP2, E. coli K12 [Simić, D., Vuković-Gacić, B., Knezević-Vukcević, J., 1998. Detection of natural bioantimutagens and their mechanisms of action with bacterial assay-system. Mutat. Res. 402, 51-57] and S. cerevisiae D7 reversion assays. The toxicity of EO differed, depending on the strain used. The most sensitive were permeable strains TA100, TA102, E. coli K12 IB112 and non-permeable WP2. Mutagenic potential of EO and monoterpenes was not detected, with or without S9. EO reduced the number of UV-induced revertants in a concentration-dependent manner, reaching 50-70% of inhibition at the maximum non-toxic concentrations: 3 microl/plate (TA102), 5 microl/plate (WP2), 7.5 microl/plate (IB112), 30 microl/plate (E. coli K12 SY252) and 60 microl/plate (D7). The metabolic activation had no effect on antimutagenic potential of EO. Similar toxicity of monoterpenes was observed in TA100, E. coli SY252 and D7, with the exception of limonene (less toxic to D7). Reduction of UV-induced revertants by non-toxic concentrations of monoterpenes, tested with SY252 and D7, reached 40-50% at 15-20 microl/plate of thujone, 10 microl/plate of cineole and 1-10 microg/plate of camphor. Limonene showed antimutagenic effect only in D7. Our data recommend sage monoterpenes for further chemoprevention studies.

Usefulness of the SOS Chromotest in the study of medicinal plants as radioprotectors

PURPOSE

The aim of this work is to investigate the usefulness of a modified protocol of the SOS Chromotest to detect antigenotoxicity activities against gamma-rays of plant extracts with proven antioxidant activity, and to elucidate the antigenotoxic mechanisms involved in radioprotection using this system.

MATERIALS AND METHODS

The methodology developed was assayed with amifostine, the most studied radioprotector, and with Phyllanthus orbicularis HBK, Cymbopogon citratus (DC) Stapf and Pinus caribaea Morelet extracts, using pre- and post-treatment procedures.

RESULTS

The P. caribaea and C. citratus extracts were antigenotoxic against gamma-rays when the cells were pre-treated with both extracts, suggesting a possible antigenotoxic action through a free radical scavenging mechanisms. Amifostine and the P. orbicularis extract were also antigenotoxic under pre- and post-treatment conditions, indicating that several antimutagenic components of this plant extract may also operate by some intracellular mechanism, unlike its antioxidant activity.

CONCLUSIONS

The results have demonstrated the usefulness of the modified SOS Chromotest assay in the screening of phytochemical radioprotectors as well as in the study of their antimutagenic mechanisms.

Evaluation of the mutagenic and antimutagenic effects of South African plants

Dichloromethane and 90% methanol extracts of 42 South African plants were screened for mutagenicity and antimutagenicity using the Salmonella/microsome mutagenicity assay (Ames) against Salmonella typhimurium TA98 and TA100 bacterial strains in the presence and absence of metabolic activator S9. The methanol extracts from whole plants of Helichrysum simillimum, Helichrysum herbaceum and Helichrysum rugulosum indicated mutagenicity. These are the first reported tests on the mutagenicity of Helichrysum species. Six species indicated antimutagenic properties, all in the presence of S9: methanol leaf extract of Bauhinia galpinii, and dichloromethane leaf extracts of Bauhinia galpinii, Clerodendrum myricoides, Datura stramonium, Buddleja saligna, Millettia sutherlandii and Sutherlandia frutescens.

Antimutagenicity of coriander (Coriandrum sativum) juice on the mutagenesis produced by plant metabolites of aromatic amines

Aromatic amines are metabolically activated into mutagenic compounds by both animal and plant systems. The 4-nitro-o-phenylenediamine (NOP) is a well-known direct-acting mutagen whose mutagenic potential can be enhanced by plant metabolism; m-phenylenediamine (m-PDA) is converted to mutagenic products detected by the Salmonella typhimurium TA98 strain, and 2-aminofluorene (2-AF) is the plant-activated promutagen most extensively studied. Plant cells activate both 2-AF and m-PDA into potent mutagens producing DNA frameshift mutations. Coriander (Coriandrum sativum) is a common plant included in the Mexican diet, usually consumed uncooked. The antimutagenic activity of coriander juice against the mutagenic activity of 4-nitro-o-phenylenediamine, m-phenylenediamine and 2-aminofluorene was investigated using the Ames reversion mutagenicity assay (his- to his+) with the S. typhimurium TA98 strain as indicator organism. The plant cell/microbe coincubation assay was used as the activating system for aromatic transformation and plant extract interaction. Aqueous crude coriander juice significantly decreased the mutagenicity of metabolized aromatic amines (AA) in the following order: 2-AF (92.43%) > m-PDA (87.14%) > NOP (83.21%). The chlorophyll content in vegetable juice was monitored and its concentration showed a positive correlation with the detected antimutagenic effect. Protein content and peroxidase activity were also determined. The concentration of coriander juice (50-1000 microl/coincubation flask) was neither toxic nor mutagenic. The similar shape of the antimutagenic response curves obtained with coriander juice and chlorophyllin (used as a subrogate molecule of chlorophyll) indicated that comparable mechanisms of mutagenic inhibition could be involved. The negative correlation between chlorophyll content and mutagenic response of the promutagenic and direct-acting used amines allows us to deduce that a chemical interaction takes place between the two molecules, leading to the inactivation of mutagenic moiety.

Assessment of the potential genotoxic risk of Phyllantus orbicularis HBK aqueous extract using in vitro and in vivo assays

Phyllanthus orbicularis HBK is an endemic Cuban plant whose aqueous extract has been proposed as an effective drug for the treatment of viral diseases. In addition, antimutagenic properties of this extract have also been reported. In the present study, the genotoxicity of this plant extract was assessed using different in vitro and in vivo assays. Results from SOS gene induction, gene reversion and conversion, and SMART assays clearly show that P. orbicularis aqueous extract does not induce either primary DNA damage or mutation. Additionally, no statistically significant difference was found in the percentage of chromosomal aberrations in Chinese hamster ovarian (CHO) cells treated with the plant extract. On the contrary, micronuclei and abnormal anaphase were induced by this extract in CHO cells. This genotoxic effect was related to a high cytotoxicity. Single spots were detected in the SMART assay. These results point to a possible aneugenic effect of the P. orbicularis aqueous extract at cytotoxic doses which are much higher than those seen by their antiviral and antimutagenic activities.

Antimutagenic mechanisms of Phyllanthus orbicularis when hydrogen peroxide is tested using Salmonella assay

Phyllanthus orbicularis is a medicinal plant, endemic to Cuba, whose aqueous extract has proven antiviral properties and antimutagenic activities against aromatic amines and hydrogen peroxide. In addition, this plant extract presents antioxidant activity. In this paper, using the Salmonella assay with the experimental approaches of co-incubation, pre- and post-treatments, it is shown that the P. orbicularis extract protects bacterial cells from oxidative damage and mutation by some intracellular mechanism, irrespective of its antioxidant activity.