Bioaccessibility of bioactive compounds present in Persea americana Mill. seed ingredient during oral-gastric digestion with antibacterial capacity against Helicobacter pylori

ETHNOPHARMACOLOGICAL RELEVANCE

In ancient Mexican cultures, the Persea americana Mill seed has been used against gastrointestinal diseases, due to high concentrations of bioactive compounds. According to Traditional Mexican Medicine, P. americana seed aqueous infusion is used against roundworms, intestinal worms, parasites, and gastrointestinal problems, in a dose taken over three or four days. In addition, Mexican Society of Natural History indicates the traditional use of P. americana seed powder as an antiparasitic, and antibacterial (MTM, 2009). On the other hand, Helicobacter pylori infection is a factor associated with the development of gastric disease, peptic ulcers as well as some types of gastric lymphomas and gastric cancer in humans; in this way is necessary scientific evidence about P. americana seed effect in gastrointestinal disease.

AIM OF THE STUDY

The work aimed to evaluate bioactive compounds bioaccessibility and antimicrobial potential against Helicobacter pylori during oral-gastric digestion in vitro of food ingredient from Persea americana Mill. seed and elucidate the possible action mechanism using in silico tools.

MATERIALS AND METHODS

Initially, P. americana seed oil and aqueous extract of P. americana seed were obtained using ultrasound and maceration respectively, and the food ingredient from P. americana seed was obtained. The samples underwent oral-gastric digestions by the INFOGEST method, to continue identifying and quantifying the bioactive compounds by HPLC-DAD and GC-MS. The anti-Helicobacter pylori activity determination were used fourteen Helicobacter pylori clinical strains and reference strains by Susceptibility testing by Minimal Inhibition Concentration, Kinetics of Growth Inhibition of H. pylori, Urease Inhibitory Kinetic. Finally, to elucidate a possible action mechanism used in silico tools (Software AutoDock 4.2.6 and BioVia Discovery v.19.1.0.1.18287).

RESULTS

The lipophilic fraction of P. americana seed detected oleic acid, linoleic acid, and avocadenofuran compounds, and the phenolic fraction showed the presence of catechin, rutin, ellagic, and chlorogenic acid, among others. Phenolic compounds conformational changes during oral-gastric digestion due to mechanical and acid hydrolysis, while lipophilic compounds showed a 20% increase in the gastric phase. Persea americana Mill. seed ingredient (3.08 μg/mL) showed total in vitro inhibition of clinical and reference strains of H. pylori, likewise, the lipophilic fraction had a lower inhibition concentration (2.59 μg/mL) regardless of the strains. Among the mechanisms found in silico, inhibition of target proteins such as CagA, BabA, and MUC5 were observed, as virulence factors involving adherence and bacterial pathogenicity.

CONCLUSIONS

This research provides evidence that food ingredient from P. americana seed has antimicrobial in vitro potential against H. pylori clinical strains, through phenolic and mainly lipophilic compounds, opening new scientific evidence that supports the P. americana seed's traditional use.

Moringa oleifera leaves alleviated inflammation through downregulation of IL-2, IL-6, and TNF-α in a colitis-associated colorectal cancer model

New chemopreventive alternatives are needed due to the rising worldwide incidence of colorectal cancer. The objective was to evaluate the chemopreventive activity of Moringa oleifera leaves (MO) in a colitis-associated colon carcinogenesis model. We hypothesized that MO contain bioactive compounds capable of modulating the expression of genes involved in the inflammatory response and carcinogenesis. Forty-eight male mice (CD-1) were divided into six groups; 1: Healthy control; 2: Positive control induced with azoxymethane (AOM, 10 mg/Kg body weight, intraperitoneal injection) and three cycles of dextran sodium sulfate (DSS, 1.5% in drinking water); groups 3, 4, and 5 were induced with AOM/DSS and supplemented with 5%, 10%, and 20% of MO, respectively; group 6: had no disease induction and supplemented with 20% of MO. Mice were treated for 12 weeks and euthanized. Significant differences (p < 0.05) were found for the moringa-administered groups in morphological and histopathological parameters compared to the AOM/DSS control. A decrease in myeloperoxidase activity (~50%) and lipid peroxidation (1.9-3.1 times) were found in groups with 10% and 20% of MO compared to the AOM/DSS control (p < 0.05). The group supplemented with 10% MO showed a significant increase (~3 times) in butyrate and propionate in fecal and cecal content. Groups supplemented with 10%, and 20% MO showed a reduction in proinflammatory cytokines in serum (MCP-1, IL-6, TNF-α) compared to the AOM/DSS control. Treatment with 10% MO induced differential expression of 65 genes in colon tissue such as IL-2, IL-6, TNF, IL-1ß, and INF-γ. MO downregulated proinflammatory mediators showing chemopreventive properties against inflammatory response and colon carcinogenesis.

Physicochemical characterization of protein isolates of amaranth and common bean and a study of their compatibility with xanthan gum

Vegetables are considered to be a sustainable source of promising biomaterials such as proteins and polysaccharides. In this study, four protein isolates (amaranth protein isolate API, amaranth globulin-rich protein isolate AGR, bean protein isolate BPI, and bean phaseolin-rich protein isolate BPR) were structurally characterized under different pH conditions (2-12) and their compatibility behavior with xanthan gum (XG) in aqueous medium was described. All protein isolates showed β turn and β sheet (78.24-81.11%), as the major secondary structures without statistically significant difference under the pH conditions surveyed. Protein isolates show solubility at pH ≤ 3 (40.4-85.1%) and pH ≥ 8 (57.6-99.9%) and surface hydrophobicity results suggest protein denaturation at pH ≤ 3. In the compatibility study, API/XG ratios between 1:1 and 5:1 at pH from 7 to 9 and the BPI/XG ratios from 1:1 to 20:1 at pH 7 form gels that do not require heating nor crosslinking agent addition. Zeta potential results, on the other hand, evidenced that formation of gels is driven by attractive electrostatic interaction of the charged regions of both biopolymers and intermolecular interactions such as hydrogen bonds.

Effect of the in vitro gastrointestinal digestion on free-phenolic compounds and mono/oligosaccharides from Moringa oleifera leaves: Bioaccessibility, intestinal permeability and antioxidant capacity

Moringa oleifera is a plant recognized for its compounds such as dietary fiber (oligosaccharides, amongst others) and polyphenols, with biological activities. These properties depend on bioactive compounds (BC) interactions with food matrix/digestion conditions, which have not been evaluated. Thus, the aim of this study was to evaluate the bioaccessibility, intestinal permeability and antioxidant capacity of BC (free-phenolic compounds (PC); and mono/oligosaccharides (MOS)) from Moringa oleifera leaves (ML) powder during in vitro gastrointestinal digestion. The gallic/caffeic acids, morin, kaempferol, mannose and stachyose showed the highest bioaccessibilities (~6-210%). The PC correlated with the antioxidant capacity (R²: 0.59-0.98, p < .05), whereas gallic/caffeic acids were the highest. The apparent permeability coefficients of bioactive compounds (0.62-36.65 × 10^-4 cm/s) and water flux/glucose transport confirmed the model similarity to in vivo experiments. The results suggest that ML digestion dynamically modifies PC/MOS bioaccessibility/antioxidant capacity while most of them are not completely absorbed in the small intestine.

Fermented non-digestible fraction from combined nixtamalized corn (Zea mays L.)/cooked common bean (Phaseolus vulgaris L.) chips modulate anti-inflammatory markers on RAW 264.7 macrophages

Chronic non-communicable diseases (NCDs) are low-level inflammation processes affected by several factors including diet. It has been reported that mixed whole grain and legume consumption, e.g. corn and common bean, might be a beneficial combination due to its content of bioactive compounds. A considerable amount would be retained in the non-digestible fraction (NDF), reaching the colon, where microbiota produce short-chain fatty acids (SCFAs) and phenolic compounds (PC) with known anti-inflammatory effect. The aim of this study was to estimate the anti-inflammatory potential of fermented-NDF of corn-bean chips (FNDFC) in RAW 264.7 macrophages. After 24 h, FNDFC produced SCFAs (0.156-0.222 mmol/l), inhibited nitric oxide production > 80% and H₂O₂ > 30%, up-regulated anti-inflammatory cytokines (I-TAC, TIMP-1) > 2-fold, and produced angiostatic and protective factors against vascular/tissue damage, and amelioration of tumor necrosis factor signalling and inflammatory bowel disease. These results confirm the anti-inflammatory potential derived from healthy corn-bean chips.

The fermented non-digestible fraction of common bean (Phaseolus vulgaris L.) triggers cell cycle arrest and apoptosis in human colon adenocarcinoma cells

Cancer is a leading cause of death worldwide with colorectal cancer (CRC) ranking as the third contributing to overall cancer mortality. Non-digestible compounds such as dietary fiber have been inversely associated with CRC in epidemiological in vivo and in vitro studies. In order to investigate the effect of fermentation products from a whole non-digestible fraction of common bean versus the short-chain fatty acid (SCFAs) on colon cancer cells, we evaluated the human gut microbiota fermented non-digestible fraction (hgm-FNDF) of cooked common bean (Phaseolus vulgaris L.) cultivar Negro 8025 and a synthetic mixture SCFAs, mimicking their concentration in the lethal concentration 50 (SCFA-LC50) of FNDF (hgm-FNDF-LC50), on the molecular changes in human colon adenocarcinoma cells (HT-29). Total mRNA from hgm-FNDF-LC50 and SCFA-LC50 treated HT-29 cells were used to perform qPCR arrays to determine the effect of the treatments on the transcriptional expression of 84 genes related to the p53-pathway. This study showed that both treatments inhibited cell proliferation in accordance with modulating RB1, CDC2, CDC25A, NFKB and E2F genes. Furthermore, we found an association between the induction of apoptosis and the modulation of APAF1, BID, CASP9, FASLG, TNFR10B and BCL2A genes. The results suggest a mechanism of action by which the fermentation of non-digestible compounds of common bean exert a beneficial effect better than the SCFA mixture by modulating the expression of antiproliferative and pro-apoptotic genes in HT-29 cells to a greater extent, supporting previous results on cell behavior, probably due to the participation of other compounds, such as phenolic fatty acids derivatives and biopetides.

Antimutagenic activity of phenolic compounds, oligosaccharides and quinolizidinic alkaloids fromLupinus campestrisseeds

There are some foods that contain mutagenic or carcinogenic agents, some of which occur naturally and others that may be formed during preparation or cooking. Several foods such as legumes, also contain natural antimutagens and/or anticarcinogens. Lupine is one such legume that contains high amounts of protein (40%) and oils (14%). About 90 species of lupine have been reported throughout Mexico. However, the use of this crop as a source of food has been limited by the presence of antinutritional agents such as phenolic compounds (PC), carbohydrates (CH) and quinolizidinic alkaloids (Qas). It has also been suggested that consuming these compounds can affect human health and may even reduce the risk of disease. The objective of this work was to determine the effect of PC, CH and Qas, isolated and quantified from Lupinus campestris on the mutagenicity of 1-nitropyrene (1-NP) as a model mutagen and we used the Salmonella typhimurium tester strain YG1024 by the Kado microsuspension method. The results indicate that L. campestris seeds have 11 mg (+)catechin equivalent g(-1) seed coat; 120.3 mg g(-1) seeds and 2.13 mg g(-1) seeds of PC, CH and Qas, respectively. 1-NP mutagenicity was inhibited by 86% for PC, 76% for CH and 75% for Qas at concentrations of 200, 512 and 13.6 microg/tube, respectively.

Purification and acute toxicity of a lectin extracted from tepary bean (Phaseolus acutifolius)

Lectins are proteins or glycoproteins known for their ability to agglutinate cells, especially erythrocytes. Several lectins are toxic to mammalian cells both in vitro and in vivo, inhibit growth when incorporated into the diet and are toxic when injected into animals. On the other hand, the use of lectins has been suggested as an alternative in cancer treatment. The objective of the present study was to evaluate the acute toxicity of a lectin extracted and purified from tepary bean (Phaseolus acutifolius, G-400-34) on CD-1 mice. Fetuin affinity chromatography, electrophoretic pattern and Western-immunoblot techniques were used to purify and partially characterize the lectin. This tepary bean line presented high levels of lectin activity. Western blot revealed that the sera reacted with the known PHA subunits in the 34-40 kD range. Four major lectin and lectin-related glycopolypeptides were identified. The purified lectin from tepary bean was a tetrameric one that ran at about 115-120 kD. The LD(50) (ip) was 1100 mg/kg body weight for males and 1120 mg/kg body weight for females. The body weight of experimental animals decreased in a dose-dependent manner. The main target organs affected were small intestine, spleen and thymus. The lectin isolated from tepary bean showed affinity towards fetuin, with high agglutination values and low acute toxicity.

Comparison of nixtamalization and extrusion processes for a reduction in aflatoxin content

Traditional nixtamalization and an extrusion method for making the dough (masa) for corn tortillas that requires using lime and hydrogen peroxide were evaluated for the detoxification of aflatoxins. The traditional nixtamalization process reduced levels of aflatoxin B(1) (AFB(1)) by 94%, aflatoxin M(1) (AFM(1)) by 90% and aflatoxin B(1)-8,9-dihydrodiol (AFB(1)-dihydrodiol) by 93%. The extrusion process reduced levels of AFB(1) by 46%, AFM(1) by 20% and AFB(1)-dihydrodiol by 53%. Extrusion treatments with 0, 0.3 and 0.5% lime reduced AFB(1) levels by 46, 74 and 85%, respectively. The inactivation of AFB(1), AFM(1) and AFB(1)-dihydrodiol in the extrusion process using lime together with hydrogen peroxide showed higher elimination of AFB(1) than treatments with lime or hydrogen peroxide alone. The extrusion process with 0.3% lime and 1.5% hydrogen peroxide was the most effective process to detoxify aflatoxins in corn tortillas, but a high level of those reagents negatively affected the taste and aroma of the corn tortilla as compared with tortillas elaborated by the traditional nixtamalization process.

Antimutagenic activity of natural phenolic compounds present in the common bean (Phaseolus vulgaris) against aflatoxin B1

Polyphenols with antimutagenic and anticarcinogenic properties are present in fruits, vegetables and legumes. In this study, the Salmonella typhimurium tester strains TA98 and TA100 were used in the microsuspension assay to examine the antimutagenic effect of phenolic compounds extracted from the common bean (Phaseolus vulgaris) against mutagenicity induced by aflatoxin B1 (AFB1). A dose-response curve was constructed for AFB1; from which a level of 40 ng AFB1/tube was selected for all antimutagenicity assays. The AFB1 and phenolic extract (PE) were not toxic to the bacteria at concentrations tested. In the case of PE, results were similar to the number of spontaneous revertants for TA98 and TA100. The inhibitory effect of PE against AFB1 mutagenicity was dose-dependent at the lower concentrations tested (2.5, 5, 10, 12.5, 15 and 25 microgram-equivalent (+)-catechin/tube for TA98; 0.5, 1, 1.5, 2.5, 5, 10 and 25 microgram-equivalent (+)-catechin/ tube for TA100). Further, a two-stage incubation procedure was used to investigate the potential interaction between PE and AFB1. The greatest inhibitory effect of the PE on AFB1 mutagenicity occurred when PE and AFB1 were incubated together. When the bacteria were first incubated with PE followed by a second incubation with AFB1, lower inhibition was observed. Lower inhibition was also observed when the bacteria were first incubated with AFB1 followed by a second incubation with PE. The results suggest that the mechanism of inhibition could involve the formation of a chemical complex between of PE and AFB1.

Antimutagenic effects of natural phenolic compounds in beans

Polyphenols in fruits, vegetables (e.g., flavonols like quercetin) and tea (e.g., catechins such as epigallocatechin gallate) are good antioxidants with antimutagenic and anticarcinogenic properties. In the present study, the Salmonella typhimurium tester strain YG1024 was used in the plate-incorporation test to examine the antimutagenic effect of phenolic compounds, extracted from common beans (Phaseolus vulgaris), on 1-NP and B[a]P mutagenicity. Dose-response curves for 1-NP and B[a]P were obtained; the number of net revertants/plate at the peak mutagenic dosage were 880 for 1-NP and 490 for B[a]P. For the antimutagenicity studies doses of 0.1 microg/plate and 2 microg/plate for 1-NP and B[a]P, respectively, were chosen. We obtained a dose-response curve of ellagic acid (EA) against B[a]P and 1-NP mutagenicity. To test the bean extract, a dose of 300 microg/plate of EA was chosen as the antimutagenic control. The EA and bean extracts were not toxic to the bacteria at the concentrations tested. The inhibitory effects of the bean extracts and EA against B[a]P mutagenicity were dose-dependent. The percentages of inhibition produced against B[a]P (2 microg/plate) using 300 microg/plate of EA and for the extracts 500 microg equivalent catechin/plate were 82%, 83%, 81% and 83% for EA, water extract, water/methanol extract and methanol extract, respectively. However, for 1-NP mutagenicity, only the methanolic extract from beans showed an inhibitory effect. These results suggest that common beans, as other legumes, can function as health-promoting foods.

Antimutagenic activity of carotenoids in green peppers against some nitroarenes

In Mexico, as well as in Central and South American countries, the consumption of peppers (Capsicum annuum) has been tradition for thousands of years; the per capita dietary intake of peppers is about 40 g/day. Peppers are an important source of beta-carotene and vitamin A, which have antimutagenic and/or anticarcinogenic properties. In the present study, Salmonella typhimurium tester strain YG1024 in the plate-incorporation test was used to examine the antimutagenicity of carotenois extracted from five different types of Capsicum spp. ('Chilaca', 'Poblano', 'Serrano', 'Jalapeño' and 'Pimiento') which were chosen, based on their consumption and availability on the local market. Extracts from these peppers were tested against 1-6-dinitropyrene (1,6-DNP) and 1,8-dinitropyrene (1,8-DNP) mutagenicity. Dose-response mutagenicity curves of 1-NP; 1,6-DNP and 1,8-DNP were obtained. For the antimutagenicity studies, doses of 0.05 microgram/plate, 0.20 ng/plate and 0.06 ng/plate for 1-NP, 1,6-DPN and 1,8-DNP respectively were chosen, and the number of net revertants/plate were 1008 for 1-NP, 512 for 1,6-DNP, and 712 for 1,8-DPN. Trans-beta-carotene and the extracts were not toxic to the bacteria at the concentrations tested. The extracts obtained from the peppers showed more inhibition than pure trans-beta-carotene on 1-NP; 1,6-DNP and 1,8-DNP mutagenicity. Chilaca pepper extract required 0.36 g (34 nmol expressed as trans-beta-carotene equivalents) of fresh pepper to inhibit 94% on 1-NP mutagenicity, 78% on 1,6-DNP mutagenicity and 84% on 1,8-DNP mutagenicity. Bell pepper ('Pimiento') extract required 1.53 g (50 nmol expressed as trans-beta-carotene) to obtain 87%, 79% and 73% inhibition on 1-NP; 1,6-DNP and 1,8-DNP mutagenicity respectively. Since pure beta-carotene inhibited only approximately 50% the mutagenicity of nitroarenes, these results suggest that each one of the pepper extracts have more than one antimutagenic compound (e.g., beta-carotene and xanthophylls) and those functional nutrients apparently have a synergistic effect.

Inhibitory effects of ellagic acid on the direct-acting mutagenicity of aflatoxin B1 in the Salmonella microsuspension assay

Ellagic acid (EA) is a phenolic compound that exhibits both antimutagenic and anticarcinogenic activity in a wide range of assays in vitro and in vivo. It occurs naturally in some foods such as strawberries, raspberries, and grapes. In the previous work, we used the Salmonella microsuspension assay to examine the antimutagenicity of EA against the potent mutagen aflatoxin B1 (AFB1) using tester strains TA98 and TA100. Briefly, the microsuspension assay was approximately 10 times more sensitive than the standard Salmonella/microsome (Ames) test in detecting AFB1 mutagenicity, and EA significantly inhibited mutagenicity of all AFB1 doses in both tester strains with the addition of S9. The greatest inhibitory effect of EA on AFB1 mutagenicity occurred when EA and AFB1 were incubated together (with metabolic enzymes). Lower inhibition was apparent when the cells were first incubated with EA followed by a second incubation with AFB1, or when the cells were first incubated with AFB1 followed by a second incubation with EA alone, all with metabolic enzymes. The result of these sequential incubation studies indicates that one mechanism of inhibition could involve the formation of an AFB1-EA chemical complex. In the present study, we further examine the effect of EA on AFB1 mutagenicity, but without the addition of exogenous metabolic enzymes. We report the mutagenicity of AFB1 in the microsuspension assay using TA98 and TA100 without the addition of S9. Neither the concentrations of AFB1 (0.6, 1.2, and 2.4 microg/tube) nor the concentrations of EA (0.3, 1.5, 3, 10, and 20 microg/tube) were toxic to the bacteria. The results indicate that AFB1 is a direct-acting mutagen, and that EA inhibits AFB1 direct-acting mutagenicity.

Genotoxicity testing of methyl tertiary-butyl ether (MTBE) in the Salmonella microsuspension assay and mouse bone marrow micronucleus test

Methyl tertiary-butyl ether (MTBE) is an oxygenated fuel additive that is present in gasoline at levels up to 15% by volume. Since the 1990 Clean Air Act amendments require the use of oxygenated gasoline in 39 areas of the USA, the use of MTBE is projected to continue to dramatically increase. As the use of MTBE increase, the potential for environmental release of MTBE from gasoline stations and automobiles will also increase. Despite its growing use as a fuel additive and its potential for increased exposure to the public, few genotoxicity data on MTBE have been published in the peer-review literature. In the present study, we tested the potential genotoxicity of MTBE in two short-term test systems, an in vitro Salmonella microsuspension assay and an in vivo mouse bone marrow micronucleus test. For the microsuspension assay, MTBE was tested at 7 dose levels of 30 to 7400 micrograms/tube in tester strain TA98, TA100, TA104, and TA1535, with and without the addition of metabolic enzymes (S9) at 4 concentration (0, 300, 600, and 1200 micrograms S9/ml final concentration). A closed system was used to minimize loss of MTBE. The response was not significant. However, a high degree of toxicity was observed at the highest doses in all tester strains. MTBE was also tested for clastogenicity i the mouse bone marrow micronucleus test using both male and female Swiss-Webster mice. Mice were administered single intraperitoneal injections of MTBE in olive oil at 5 doses ranging from 0.25 to 1.75 g/kg. There were no significant increases in micronucleus formation at any dose of MTBE when compared with the negative control animals receiving only olive oil. MTBE was not positive when tested for point mutations and clastogenicity, using respectively, a Salmonella microsuspension assay and the mouse bone marrow micronucleus test.

Antimutagenicity of xanthophylls present in Aztec Marigold (Tagetes erecta) against 1-nitropyrene

The principal natural food colorants used in modern food manufacture are anthocyanins, betalains, carotenoids, chlorophylls, riboflavin and caramel. Carotenoids (carotenes and xanthophylls) occur naturally in some foods such as carrots, red tomatoes, butter, cheese, paprika, palm oil, corn kernels, marigold petals, annatto, and red salmon. Carotenoids (alpha- or beta-carotene and xanthophylls) are excellent antioxidants and inhibit some types of cancers. In the present study, we used the Salmonella typhimurium tester strain YG1024 in the plate-incorporation test to examine the antimutagenicity of xanthophylls extracted from Aztec Marigold (Tagetes erecta) on 1-nitropyrene (1-NP) mutagenicity. Further, we investigated the effect of lutein on DNA-repair system of tester strain YG1024, using a preincubation test. The possible mechanism of lutein on 1-NP mutagenicity was studied by comparing the absorption spectrum of lutein, 1-NP and lutein plus 1-NP. In a dose-response curve of 1-NP, the mutagenic potency was 4317 revertants/nmol, and the dose of 0.06 microgram of 1-NP/plate was chosen for the antimutagenicity studies. Lutein and xanthophylls from Aztec Marigold (pigments for poultry and human use) inhibited mutagenicity of 1-NP in a dose-dependent manner. Lutein and the pigments were not toxic to the bacteria at the concentrations tested (0.002, 0.02, 0.2, 2.0 and 10 micrograms/plate). The percentages of inhibition of 1-NP mutagenicity were 72%, 92% and 66.2% for lutein (10 micrograms/plate), pigment for poultry use (10 micrograms/plate) and pigment for human use (2 micrograms/plate), respectively. Lutein had no effect on the DNA-repair system of strain YG1024. A new peak was detected at 429 nm when lutein was added at 1-NP, and it was stable throughout the incubation time. The results suggest that the major mechanisms of lutein against 1-NP mutagenicity is the potential formation of a complex between lutein and 1-NP, which could limit the bioavailability of 1-NP.

Antimutagenic activity of natural xanthophylls against aflatoxin B1 in Salmonella typhimurium

Carotenoids (carotenes and xanthophylls) are excellent antioxidants with antimutagenic and anticarcinogenic properties. They occur naturally in some foods such as carrots, red tomatoes, butter, cheese, paprika, palm oil, corn kernels, Marigold petals, annatto, and red salmon. In the present study, we used the Salmonella plate incorporation test to examine the effect of xanthophylls extracted from Aztec Marigold (Tagetes erecta) on the AFB1 mutagenicity, using tester strain YG1024. The effect of lutein on the DNA-repair system in YG1024 was investigated by a pre-incubation test. In a dose-response curve of AFB1, the mutagenic potency was 1,031 revertants/nmol. The dose of 0.5 microgram AFB1/ plate was chosen for the antimutagenicity studies. Pure lutein and xanthophylls from Aztec Marigold flower (oleoresin and xanthophyll plus) inhibited the mutagenicity of AFB1 in a dose-dependent manner. The pigments were more efficient at inhibiting the AFB1 mutagenicity than pure lutein. The percentages of inhibition on AFB1 mutagenicity were 37, 66, and 76% for lutein, oleoresin, and xanthophyll plus at the dose of 2 micrograms/plate, respectively. Lutein had a modest effect on the DNA-repair system of YG1024. In spectrophotometric studies, a new absorption peak was detected at 378 nm when lutein and AFB1 were incubated together, and lutein reacted with AFB1 metabolites. The results suggest that the inhibitory mechanism of lutein against AFB1 mutagenicity is most probably the result of a combination of the following events: formation of a complex between lutein and AFB1, direct interaction between lutein and AFB1 metabolites, and finally that the lutein may also affect the metabolic activation of AFB1 by S9 and the expression of AFB1-modified Salmonella DNA.

Antimutagenicity of ellagic acid against aflatoxin B1 in the Salmonella microsuspension assay

Ellagic acid (EA) is a phenolic compound with antimutagenic and anticarcinogenic properties. It occurs naturally in some foods such as strawberries, raspberries, grapes, black currants and walnuts. In the present study, we used the Salmonella microsuspension assay to examine the antimutagenicity of EA against the potent mutagen aflatoxin B1 (AFB1) using tester strains TA98 and TA100. Further, we used a two-stage incubation procedure that incorporates washing the bacterial cells free of the incubation mixture after the first incubation to investigate EA and AFB1 interaction. Three different concentrations of AFB1 (2.5, 5 and 10 ng/tube) were tested against five different concentrations of EA for TA98 and TA100. EA significantly inhibited mutagenicity of all doses of AFB1 in both tester strains with the addition of S9. EA alone was not mutagenic at the concentrations tested. The greatest inhibitory effect of EA on AFB1 mutagenicity occurred when EA and AFB1 were incubated together. Lower inhibition was apparent when the cells were first incubated with EA followed by a second incubation with AFB1, and also when the cells were first incubated with AFB1 followed by a second incubation with EA alone. The results of the sequential incubation studies support the hypothesis that one mechanism of inhibition could involve the formation of a chemical complex between EA and AFB1.