Genotoxicity and antigenotoxicity of the methanol extract of Cleistocalyx nervosum var. paniala seed using a Salmonella mutation assay and rat liver micronucleus tests

Genotoxic and Anti-Genotoxic Assessments of Fermented Houttuynia cordata Thunb. Leaf Ethanolic Extract and Its Anti-Cancer Effect in a Dual-Organ Carcinogenesis Model of Colon and Liver in Rats

The incidence of multiple-organ cancers has recently increased due to simultaneous exposure to various environmental carcinogens. Houttuynia cordata Thunb. (H. cordata) is recognized for its many health benefits, including its anti-cancer properties. The fermentation of its leaves has been shown to significantly enhance the bioflavonoid content and its bioactivities. This study aimed to evaluate the effectiveness of fermented H.cordata leaf (FHCL) extracts against combined carcinogens and investigate the underlying mechanisms. The crude ethanolic extract of FHCL was partitioned to obtain hexane- (HEX), dichloromethane- (DCM), ethyl acetate- (ETAC), butanol- (nBA), and residue fractions. The crude ethanolic extract (200-250 μg/mL) and the DCM fraction (50 μg/mL) significantly reduced NO production in RAW264.7 macrophages. In addition, the crude extract and the DCM and ETAC fractions showed anti-genotoxicity against aflatoxin B1 and 2-amino-3,4-dimethylimidazo [4,5-f]quinoline (MeIQ) in Salmonella typhimurium assays (S9+). Despite demonstrating genotoxicity in the Salmonella mutation assay (with and without S9 activation), oral administration of the crude extract at 500 mg/kg of body weight (bw) for 40 days in rats did not induce micronucleated hepatocytes, indicating that the extract is non-genotoxic in vivo. Moreover, the crude extract significantly decreased Phase I but increased Phase II xenobiotic-metabolizing enzyme activities in the rats. Next, the anti-cancer effects of FHCL were evaluated in a dual-organ carcinogenesis model of the colon and liver in rats induced by 1,2-dimethylhydrazine (DMH) and diethylnitrosamine (DEN), respectively. The crude extract significantly reduced not only the number and size of glutathione S-transferase placental form positive foci in the liver (at doses of 100 and 500 mg/kg bw) but also the number of aberrant crypt foci in rat colons (at 500 mg/kg bw). Furthermore, FHCL significantly reduced the expression of proliferating cell nuclear antigen (PCNA) in the colon (at 100 and 500 mg/kg bw) and liver (at 500 mg/kg bw) of the treated rats. In conclusion, FHCL exhibits significant preventive properties against colon and liver cancers in this dual-organ carcinogenesis model. Its mechanisms of action may involve anti-inflammatory effects, the prevention of genotoxicity, the modulation of xenobiotic-metabolizing enzymes, and the inhibition of cancer cell proliferation. These findings support the use of FHCL as a natural supplement for preventing cancer.

Thai Fermented Soybean (Thua-Nao) Prevents Early Stages of Colorectal Carcinogenesis Induced by Diethylnitrosamine and 1,2-Dimethylhydrazine Through Modulations of Cell Proliferation and Gut Microbiota in Rats

BACKGROUND

Thua-nao is a traditional fermented soybean product widely consumed in the northern areas of Thailand. There has been little research on the biological activity of Thua-nao, particularly its anticancer properties.

OBJECTIVES

The objective of this study was to examine the cancer chemopreventive effects of dried Thua-nao on liver and colorectal carcinogenesis induced by carcinogens in rats.

METHODS

Rats were injected with diethylnitrosamine (DEN) and 1,2-dimethylhydrazine (DMH) to induce preneoplastic lesions. Rats orally received dried Thua-nao for 13 weeks. The preneoplastic lesions, including glutathione S-transferase placental form (GST-P)-positive foci and aberrant crypt foci (ACF), were evaluated in the liver and colon, respectively. The cancer chemopreventive mechanisms of dried Thua-nao on liver and colorectal carcinogenesis were examined.

RESULTS

Dried Thua-nao administration suppressed colorectal aberrant crypt foci. Moreover, dried Thua-nao reduced proliferation cell nuclear antigen (PCNA)-positive cells in the colon. Interestingly, dried Thua-nao modulated the gut microbiota in DEN- and DMH-induced rats. Isoflavones, including genistein and daidzein, represent promising chemopreventive agents in dried Thua-nao.

CONCLUSIONS

In conclusion, these results highlight the cancer chemopreventive effect of dried Thua-nao in DEN and DMH-induced colorectal carcinogenesis through cell proliferation reduction and gut microbiota modulation.

Cancer Chemopreventive Effect of 2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone on Diethylnitrosamine-Induced Early Stages of Hepatocarcinogenesis in Rats

2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC) is a major compound in Cleistocalyx nervosum seed extract (CSE), which has been reported to have various biological activities, including anti-cancer activity. Therefore, this study attempted to evaluate whether DMC is a chemopreventive compound in CSE. Moreover, the preventive mechanisms of CSE and DMC in the DEN-induced early stages of hepatocarcinogenesis in rats were investigated. Male Wistar rats were intraperitoneally injected with DEN 50 mg/kg bw once a week for 8 weeks. Rats received CSE and DMC orally throughout the experiment. The number of glutathione S-transferase placental form (GST-P)-positive foci in the liver was measured. Furthermore, the preventive mechanisms of CSE and DMC on DEN-induced HCC, including cell proliferation and apoptosis, were investigated. Administering CSE at a dosage of 400 mg/kg bw and DMC at a dosage of 10 mg/kg bw significantly decreased the number and size of GST-P-positive foci and GST-P expression. In addition, DMC inhibited the development of preneoplastic lesions by decreasing cell proliferation and causing cell apoptosis; however, CSE inhibited the development of preneoplastic lesions by inducing cell apoptosis. In conclusion, DMC exhibited a cancer chemopreventive effect on the early stages of hepatocarcinogenesis by increasing cell apoptosis and reducing cell proliferation.

Chemopreventive Potential of Phyllanthus emblica Fruit Extract against Colon and Liver Cancer Using a Dual-Organ Rat Carcinogenesis Model

Humans are frequently exposed to various carcinogens capable of inducing cancer in multiple organs. Phyllanthus emblica (P. emblica) is known for its strong antioxidant properties and potential in cancer prevention. However, its effectiveness against combined carcinogens remains relatively unexplored. This study aimed to assess the chemopreventive potential of the ethanolic extract of P. emblica fruits against preneoplastic lesions in the liver and colon using a rat model. Rats were administered with diethylnitrosamine (DEN) and 1,2-dimethylhydrazine (DMH) to induce hepato- and colon carcinogenesis, respectively. The ethanolic extract of P. emblica fruit at 100 and 500 mg/kg bw significantly reduced the number of preneoplastic lesions in the liver by 74.7% and 55.6%, respectively, and in the colon by 39.2% and 40.8%, respectively. Similarly, the extract decreased the size of preneoplastic lesions in the liver by 75.2% (100 mg/kg bw) and 70.6% (500 mg/kg bw). Furthermore, the extract significantly reduced the cell proliferation marker in the liver by 70.3% (100 mg/kg bw) and 61.54% (500 mg/kg bw), and in the colon by 62.7% (100 mg/kg bw) and 60.5% (500 mg/kg bw). The ethanolic extract also enhanced liver antioxidant enzyme activities and demonstrated free radical scavenging in DPPH, ABTS, and FRAP assays. Additionally, the dichloromethane fraction of P. emblica showed significant cancer prevention potential by reducing intracellular ROS and NO production by 61.7% and 35.4%, respectively, in RAW 264.7 macrophages. It also exhibited antimutagenic effects with a reduction of 54.0% against aflatoxin B1 and 52.3% against 2-amino-3,4-dimethylimidazo[4,5-f]quinoline-induced mutagenesis in Salmonella typhimurium. Finally, this study highlights the chemopreventive activity of P. emblica fruit extract against the initiation of early-stage carcinogenic lesions in the liver and colon in rats treated with dual carcinogens.

Guidance for the use and interpretation of assays for monitoring anti-genotoxicity

Since DNA damage can occur spontaneously or be produced by the environmental genotoxins in living cells, it is important to investigate compounds that can reverse or protect DNA damage. An appropriate methodology is essential for the responsive identification of protection offered against DNA damage. This review includes information on the current state of knowledge on prokaryotic cell-based assays (SOS chromotest, umu test, vitotox assay) and cytogenetic techniques (micronucleus assay, chromosome aberration test and sister chromatid exchange assay) with an emphasis on the possibility to explore genoprotective compounds. Throughout the last decade, studies have extrapolated the scientific methodologies utilized for genotoxicity to assess genoprotective compounds. Therefore, shortcomings of genotoxicity studies are also mirrored in antigenotoxicity studies. While regulatory authorities around the world (OECD, US-EPA and ICH) continue to update diverse genotoxic assay strategies, there are still no clear guidelines/approaches for efficient experimental design to screen genoprotective compounds. As a consequence, non-synergetic and inconsistent implementation of the test method by the researchers to execute such simulations has been adopted, which inevitably results in unreliable findings. The review has made the first attempt to collect various facets of experimentally verified approaches for evaluating genoprotective compounds, as well as to acknowledge potential significance and constraints, and further focus on the assessment of end points which are required to validate such action. Henceforth, the review makes an incredible commitment by permitting readers to equate several components of their test arrangement with the provided simplified information, allowing the selection of convenient technique for the predefined compound from a central repository.

2,4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone from Cleistocalyx nervosum var. paniala seeds attenuated the early stage of diethylnitrosamine and 1,2-dimethylhydrazine-induced colorectal carcinogenesis

BACKGROUND

Dichloromethane extract of Cleistocalyx nervosum var. paniala seeds exhibited an anticarcinogenicity against chemically-induced the early stages of carcinogenesis in rats. This study aimed to identify anticarcinogenic compounds from C. nervosum seed extract (CSE).

METHODS

Salmonella mutation assay was performed to determine mutagenicity and antimutagenicity of partially purified and purified compounds of CSE. The anticarcinogenic enzyme-inducing activity was measured in Hepa1c1c7. Moreover, the anticancer potency was examined on various human cancer cell lines. The anticarcinogenicity of DMC was investigated using dual-organ carcinogenicity model. The number of preneoplastic lesions was evaluated in the liver and colon. The inhibitory mechanisms of DMC on liver- and colorectal carcinogenesis were investigated.

RESULTS

Six partially purified fractions (MK1 - MK6) and purified compounds, including 2,4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC) and hariganetin, were obtained from CSE. Among these fractions, MK4 and DMC presented the greatest antimutagenicity against indirect mutagens in bacterial model. Moreover, MK5 possessed an effective anticarcinogenic enzyme inducer in Hepa1c1c7. The MK4, DMC and CSE showed greater anticancer activity on all cell lines and exhibited the most effective toxicity on colon cancer cells. Furthermore, DMC inhibited the formation of colonic preneoplastic lesions in carcinogens-treated rats. It reduced PCNA-positive cells and frequency of BCAC in rat colon. DMC also enhanced the detoxifying enzyme, GST, in rat livers.

CONCLUSIONS

DMC obtained from CSE may be a promising cancer chemopreventive compound of colorectal cancer process in rats. It could increase detoxifying enzymes and suppress the cell proliferation process resulting in prevention of post-initiation stage of colorectal carcinogenesis.

2',4'-Dihydroxy-6'‑methoxy-3',5'-dimethylchalcone and its amino acid-conjugated derivatives induce G0/G1 cell cycle arrest and apoptosis via BAX/BCL2 ratio upregulation and in silico insight in SiHa cell lines

We modified the chemical structure of 2',4'-dihydroxy-6'‑methoxy-3',5'-dimethylchalcone (DMC, 1), a phytochemical found in the seed of Syzygium nervosum A.Cunn. ex DC., by conjugation with the amino acid L-alanine (compound 3a) or L-valine (compound 3b) to enhance anticancer activity and water solubility. Compounds 3a and 3b had antiproliferative activity in human cervical cancer cell lines (C-33A, SiHa and HeLa), with half-maximal inhibitory concentrations (IC₅₀) of 7.56 ± 0.27 and 8.24 ± 0.14 µM, respectively in SiHa cells; these values were approximately two-fold greater than DMC. We investigated the biological activities of compounds 3a and 3b based on a wound healing assay, a cell cycle assay and messenger RNA (mRNA) expression analysis to determine the possible mechanism of anticancer activity. Compounds 3a and 3b inhibited SiHa cell migration in the wound healing assay. After treatment with compounds 3a and 3b, there was an increase in SiHa cells in the G1 phase, indicative of cell cycle arrest. Moreover, compound 3a showed potential anticancer activity by upregulating TP53 and CDKN1A that resulted in upregulation of BAX and downregulation of CDK2 and BCL2, leading to apoptosis and cell cycle arrest. The BAX/BCL2 expression ratio was increased after treatment with compound 3avia the intrinsic apoptotic pathway. In silico molecular dynamics simulation and binding free energy calculation shed light on how these DMC derivatives interact with the HPV16 E6 protein, a viral oncoprotein associated with cervical cancer. Our findings suggest that compound 3a is a potential candidate for anti-cervical cancer drug development.

Cleistocalyx nervosum var. paniala Berry Promotes Antioxidant Response and Suppresses Glutamate-Induced Cell Death via SIRT1/Nrf2 Survival Pathway in Hippocampal HT22 Neuronal Cells

Excessive glutamate neurotransmitters result in oxidative neurotoxicity, similar to neurodegeneration. An indigenous berry of Thailand, Cleistocalyx nervosum var. paniala (CNP), has been recognized for its robust antioxidants. We investigated the effects and mechanisms of CNP fruit extracts on antioxidant-related survival pathways against glutamate-induced neurotoxicity. The extract showed strong antioxidant capability and had high total phenolic and flavonoid contents, particularly resveratrol. Next, the protective effects of the CNP extract or resveratrol on the glutamate-induced neurotoxicity were examined in HT22 hippocampal cells. Our investigation showed that the pretreatment of cells with the CNP extract or resveratrol attenuated glutamate-induced neuronal death via suppression of apoptosis cascade by inhibiting the levels of cleaved- and pro-caspase-3 proteins. The CNP extract and resveratrol suppressed the intracellular ROS by increasing the mRNA expression level of antioxidant enzymes (SODs, GPx1, and CAT). We found that this extract and resveratrol significantly increased SIRT1 expression as a survival-related protein. Moreover, they also promoted the activity of the Nrf2 protein translocation into the nucleus and could bind to the promoter containing the antioxidant response element, inducing the expression of the downstream GPx1-antioxidant protein. Our data illustrate that the CNP extract and resveratrol inhibit apoptotic neuronal death via glutamate-induced oxidative neurotoxicity in HT22 cells through the activation of the SIRT1/Nrf2 survival mechanism.

Effects of 2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone from Syzygium nervosum Seeds on Antiproliferative, DNA Damage, Cell Cycle Arrest, and Apoptosis in Human Cervical Cancer Cell Lines

2',4'-Dihydroxy-6'-methoxy-3',5'-dimethylchalcone (DMC), a natural product derived from Syzygium nervosum A. Cunn. ex DC., was investigated for its inhibitory activities against various cancer cell lines. In this work, we investigated the effects of DMC and available anticervical cancer drugs (5-fluorouracil, cisplatin, and doxorubicin) on three human cervical cancer cell lines (C-33A, HeLa, and SiHa). DMC displayed antiproliferative cervical cancer activity in C-33A, HeLa, and SiHa cells, with IC50 values of 15.76 ± 1.49, 10.05 ± 0.22, and 18.31 ± 3.10 µM, respectively. DMC presented higher antiproliferative cancer activity in HeLa cells; therefore, we further investigated DMC-induced apoptosis in this cell line, including DNA damage, cell cycle arrest, and apoptosis assays. As a potential anticancer agent, DMC treatment increased DNA damage in cancer cells, observed through fluorescence inverted microscopy and a comet assay. The cell cycle assay showed an increased number of cells in the G0/G1 phase following DMC treatment. Furthermore, DMC treatment-induced apoptosis cell death was approximately three- to four-fold higher compared to the untreated group. Here, DMC represented a compound-induced apoptosis for cell death in the HeLa cervical cancer cell line. Our findings suggest that DMC, a phytochemical agent, is a potential candidate for antiproliferative cervical cancer drug development.

Antigenotoxic Effects and Possible Mechanism of Red Yeast (Sporidiobolus pararoseus) on Aflatoxin B1-Induced Mutagenesis

Red yeast (Sporidiobolus pararoseus), obtained from glycerol waste in the biodiesel process, has been used as a mycotoxin sorbent in some agricultural products. This study focused on the antigenotoxic effects of red yeast on aflatoxin B₁ (AFB₁)-induced mutagenesis, using a Salmonella mutation assay and a rat liver micronucleus test. Red yeast was sequentially extracted to obtain hexane, acetone, hot water, and residue fractions. Carbohydrates were mainly found in hot water extract (HWE), while proteins were observed in the residue fraction. The amount of lycopene in hexane extract (HE) was higher than the amount of β-carotene in HE. All red yeast extracts were not mutagenic in the Salmonella typhimurium strains TA98 and TA100 under the presence and absence of metabolic activation. Among the extracts obtained from red yeast, HE presented the strongest antimutagenicity against AFB₁-induced mutagenesis in both strains, but HWE did not show any antimutagenicity. The oral administration of red yeast, HE, and HWE for 28 days was further investigated in rats. These extracts did not induce micronucleated hepatocytes. Furthermore, they modulated the activities of some detoxifying enzymes but did not alter the activities of various cytochrome P450 isozymes. Notably, they significantly decreased hepatic micronucleus formation in AFB₁-initiated rats. HE altered the activity of hepatic glutathione-S-transferase but did not affect its protein expression. Taken together, the antigenotoxicity of red yeast against AFB₁-induced mutagenesis might be partly due to the modulation of some detoxifying enzymes in AFB₁ metabolism. β-Carotene and lycopene might be promising antigenotoxic compounds in red yeast.

Low-polar extract from seed of Cleistocalyx nervosum var. paniala modulates initiation and promotion stages of chemically-induced carcinogenesis in rats

BACKGROUND

Cleistocalyx nervosum var. paniala is a local fruit mainly cultivated in the north of Thailand. Our previous study has reported that the methanol extract of C. nervosum seed presented antimutagenicity in a Salmonella mutation assay. The present study focused on the effect of a low-polar extract of C. nervosum seed on the early stages of diethylnitrosamine (DEN)- and dimethylhydrazine (DMH)-induced carcinogenesis in rats.

METHODS

Dried C. nervosum seed powder was extracted using dichloromethane. To study its effect on the initiation stage of carcinogenesis of rats, they were fed with various doses of C. nervosum seed extract (CSE) for 21 days. DEN injection was used to initiate hepatocarcinogenesis and partial hepatectomy was performed to amplify mutated hepatocytes resulting in micronucleated hepatocyte formation. To study the role of CSE on the promotion stage, rats were injected with DEN and DMH to induce preneoplastic lesions and the numbers of glutathione S-transferase placental form (GST-P) positive foci in the liver and aberrant crypt foci (ACF) in the colon were measured. This was followed by CSE administration for 10 weeks. The inhibitory mechanisms of CSE on initiation and promotion stages, including xenobiotic metabolism, cell proliferation and apoptosis, were investigated.

RESULTS

The total phenolic content in CSE was 80.34 ± 2.29 mg gallic acid equivalents (GAE) per g of extract and 2,4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone was found to be a major flavonoid. The main terpenoids in CSE were β-selinene, α-selinene, γ-selinene and o-cymene while 24(Z)-methyl-25-homocholesterol was a major phytosterol. CSE significantly decreased the number of micronucleated hepatocytes in DEN-initiated rats and enhanced the activities of hepatic glutathione S-transferase and UDP-glucuronyltransferase. Furthermore, the formation of preneoplastic lesions in the liver and colon was statistically reduced by CSE. CSE also diminished cell proliferation in the liver and colon indicated by the number of PCNA positive cells. However, CSE did not alter the numbers of apoptotic hepatocytes and colonocytes in DEN- and DMH-initiated rats.

CONCLUSIONS

The dichloromethane extract of C. nervosum seed demonstrated chemopreventive effects on chemically-induced carcinogenesis in both initiation and promotion stages in rats. The inhibitory mechanism might be involved in the modulation of hepatic detoxifying enzymes and suppression of hepatocyte and colonocyte proliferation.

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.

Ethnopharmacology, Phytochemistry, and Pharmacology of Syzygium nervosum

Syzygium nervosum, which belongs to the Myrtaceae plant family, is widely distributed and cultivated in South East Asian countries. The decoction of S. nervosum leaves and flower buds has been consumed regularly as a beverage among the Vietnamese and Chinese communities. In addition, it has also been used in traditional medicine for a variety of purposes, notably for influenza, skin diseases, and digestive conditions. To date, there has been a considerable number of publications on chemical profiling and pharmacological activities of S. nervosum crude extract and pure isolated compounds. Our analysis indicated the characteristic chemical scaffolds and potential bioactivities on cancer, diabetes, and inflammatory diseases of this plant. The review aims to summarize up-to-date past study results and suggest future research direction on this species, in order to promote clinical applications of S. nervosum.

Antiaging, Stress Resistance, and Neuroprotective Efficacies of Cleistocalyx nervosum var. paniala Fruit Extracts Using Caenorhabditis elegans Model

Plant parts and their bioactive compounds are widely used by mankind for their health benefits. Cleistocalyx nervosum var. paniala is one berry fruit, native to Thailand, known to exhibit various health benefits in vitro. The present study was focused on analyzing the antiaging, stress resistance, and neuroprotective effects of C. nervosum in model system Caenorhabditis elegans using physiological assays, fluorescent imaging, and qPCR analysis. The results suggest that the fruit extract was able to significantly extend the median and maximum lifespan of the nematode. It could also extend the healthspan by reducing the accumulation of the “age pigment” lipofuscin, inside the nematode along with regulating the expression of col-19, egl-8, egl-30, dgk-1, and goa-1 genes. Further, the extracts upregulated the expression of daf-16 while downregulating the expression of daf-2 and age-1 in wild-type nematodes. Interestingly, it could extend the lifespan in DAF-16 mutants suggesting that the extension of lifespan and healthspan was dependent and independent of DAF-16-mediated pathway. The fruit extract was also observed to reduce the level of Reactive Oxygen Species (ROS) inside the nematode during oxidative stress. The qPCR analysis suggests the involvement of skn-1 and sir-2.1 in initiating stress resistance by activating the antioxidant mechanism. Additionally, the fruit could also elicit neuroprotection as it could extend the median and maximum lifespan of transgenic strain integrated with Aβ. SKN-1 could play a pivotal role in establishing the antiaging, stress resistance, and neuroprotective effect of C. nervosum. Overall, C. nervosum can be used as a nutraceutical in the food industry which could offer potential health benefits.

Inhibitory effect of purple rice husk extract on AFB1-induced micronucleus formation in rat liver through modulation of xenobiotic metabolizing enzymes

Background

Rice husk, a waste material produced during milling, contains numerous phytochemicals that may be sources of cancer chemopreventive agents. Various biological activities of white and colored rice husk have been reported. However, there are few comparative studies of the cancer chemopreventive effects of white and colored rice husk.

Methods

This study investigated the cancer chemopreventive activities of two different colors of rice husk using in vitro and in vivo models. A bacterial mutation assay using Salmonella typhimurium strains TA98 and TA100 was performed; enzyme induction activity in murine hepatoma cells was measured, and a liver micronucleus test was performed in male Wistar rats.

Results

The white rice husk (WRHE) and purple rice husk (PRHE) extracts were not mutagenic in Salmonella typhimurium TA98 or TA100 in the presence or absence of metabolic activation. However, the extracts exhibited antimutagenicity against aflatoxin B₁ (AFB₁) and 2-amino-3,4 dimethylimidazo[4,5-f]quinolone (MeIQ) in a Salmonella mutation assay. The extracts also induced anticarcinogenic enzyme activity in a murine Hepa1c1c7 hepatoma cell line. Interestingly, PRHE but not WRHE exhibited antigenotoxicity in the rat liver micronucleus test. PRHE significantly decreased the number of micronucleated hepatocytes in AFB₁-initiated rats. PRHE contained higher amounts of phenolic compounds and vitamin E than WRHE in both tocopherols and tocotrienols as well as polyphenol such as cyanidin-3-glucoside, protocatechuic acid and vanillic acid. Furthermore, PRHE increased CYP1A1 and 1A2 activities while decreasing CYP3A2 activity in the livers of AFB₁-treated rats. PRHE also enhanced various detoxifying enzyme activities, including glutathione S-transferase, NAD(P)H quinone oxidoreductase and heme oxygenase.

Conclusions

PRHE showed potent cancer chemopreventive activity in a rat liver micronucleus assay through modulation of phase I and II xenobiotic metabolizing enzymes involved in AFB₁ metabolism. Vitamin E and phenolic compounds may be candidate antimutagens in purple rice husk.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2647-9) contains supplementary material, which is available to authorized users.

Antimutagenic and Antioxidant Activities of Thai Rice Brans

Background

Rice bran is the outer layer of the rice grain, and contains high amounts of bioactive phytochemicals. Here, we investigated and compared chemopreventive properties of purple and white rice bran extracts.

Methods

Rice bran was extracted with dichloromethane and methanol. Chemical constituents in the extracts were analyzed by colorimetric assay and high performance liquid chromatography. The mutagenicity and antimutagenicity of the extracts were determined via the Salmonella mutation assay. The anticarcinogenic enzyme induction and antioxidant activities of the extracts were examined using Hepa1c1c7 cells and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay, respectively.

Results

The methanol extracts of rice bran contained high amounts of phenolic acids, flavonoids, anthocyanins, and phytic acid, whereas large amounts of γ-oryzanol and vitamin E were presented in the dichloromethane extract. None of the extracts were mutagenic to Salmonella typhimurium. All rice bran extracts had strong antimutagenic effects against aflatoxin B₁- and 2-amino-3,4-dimethylimidazo [4,5-f]quinoline-induced mutagenesis. The inhibitory effect against 2-aminofluorene-induced mutagenesis was found in the dichloromethane extract, while only the methanol extract of purple rice bran exhibited antimutagenic effects against benzo(a)pyrene. None of the extracts induced quinone reductase activity in Hepa1c1c7 cells. Additionally, the greatest antioxidant capacity was found in the methanol extract of purple rice bran.

Conclusions

The methanol extract of purple rice bran containing high amount of phenolic acids, flavonoids, anthocyanins, and phytic acid showed the most effective antioxidant and antimutagenic activities by inhibiting mutagenic metabolizing enzymes and/or scavenging free radicals. These results demonstrate the nutritional and medical value of Thai rice for cancer prevention.

Cleistocalyx nervosum var. paniala berry fruit protects neurotoxicity against endoplasmic reticulum stress-induced apoptosis

Oxidative and endoplasmic reticulum (ER) stresses cause neuronal damage leading to neurodegenerative disorders. Cleistocalyx nervosum var. paniala (CNP) berry fruit has been shown to possess powerful antioxidant properties. Here, we investigated the neuroprotective effect of CNP extract against glutamate-mediated oxidative/ER stress-induced cell death in mouse hippocampal neuronal HT22 cells. CNP extract was clarified for its radical scavenging activities, total phenolic and anthocyanin contents. The key anthocyanin cyanidin-3-glucoside was used as a marker to standardize the extract used in the study. We found that pretreated cells with CNP extract (0.05-1 μg/ml) prevented neuronal cell death in response to 5 mM glutamate evaluated by cell viability MTT, LDH and apoptosis/necrosis Annexin V/propidium iodide co-staining assays. For mechanistic approach, glutamate-induced cell death through reactive oxygen species (ROS)-mediated ER stress pathways, indicating the increase of ROS and ER stress signature molecules including calpain, caspases-12 and C/EBP homologous proteins (CHOP). CNP extract inhibited ROS production. Moreover, the extract also suppressed the specific-ER stress apoptotic proteins level in glutamate-induced cells by upregulating the gene expression of cellular antioxidant enzymes (SODs, CAT, GPx and GSTs). Taken together, our results provide information about and the molecular mechanism of CNP extract as a promising neuroprotectant and antioxidant.

Purple rice bran extract attenuates the aflatoxin B1-induced initiation stage of hepatocarcinogenesis by alteration of xenobiotic metabolizing enzymes

Pigmented rice bran has been suggested to be a valuable source of beneficial phytochemicals. We investigated genotoxic and anti-genotoxic effects of purple rice bran extract (PRBE) in rats using a liver micronucleus assay. Purple rice bran was extracted with methanol, obtaining large amounts of phenolic compounds, including anthocyanins and small amounts of gamma-oryzanol. The experimental protocols were divided into two sets. Male rats were divided into three groups. Group 1 was a negative control, while Groups 2 and 3 were fed with 100 and 500 mg/kg bw of PRBE, respectively, for 28 days. PRBE had no effect on micronucleus formation or xenobiotic metabolizing enzymes in rat liver. Experiments concerning the effect of PRBE on AFB1 showed that PRBE significantly lessened the amount of micronucleated hepatocytes in AFB1 treated rats. Furthermore, it modulated metabolic activation of AFB1 metabolism in the liver by suppressing activity and protein expression of CYP1A2, CYP3A and CYP 450 reductase, and enhancing phase II enzymes including GST and UGT. Overall, purple rice bran extract was not genotoxic in rats. It exhibited anti-genotoxicity by modulation some xenobiotic enzymes active in AFB1 metabolism.

Protective Effect of Cleistocalyx nervosum var. paniala Fruit Extract against Oxidative Renal Damage Caused by Cadmium

Cadmium nephrotoxicity is a serious environmental health problem as it will eventually end up with end stage renal disease. The pathobiochemical mechanism of this toxic heavy metal is related to oxidative stress. This study investigated whether Cleistocalyx nervosum var. paniala fruit extract (CNFE) could protect the kidney against oxidative injury caused by cadmium. Initial analysis of the extract revealed antioxidant abilities and high levels of polyphenols, particularly catechin. Its potential renal benefits was further explored in rats treated with vehicle, CNFE, cadmium (2 mg/kg), and cadmium plus CNFE (0.5, 1, 2 g/kg) for four weeks. Oxidative renal injury was developed after cadmium exposure as evidenced by blood urea nitrogen and creatinine retention, glomerular filtration reduction, renal structural damage, together with increased nitric oxide and malondialdehyde, but decreased antioxidant thiols, superoxide dismutase, and catalase in renal tissues. Cadmium-induced nephrotoxicity was diminished in rats supplemented with CNFE, particularly at the doses of 1 and 2 g/kg. It is concluded that CNFE is able to protect against the progression of cadmium nephrotoxicity, mostly via its antioxidant power. The results also point towards a promising role for this naturally-occurring antioxidant to combat other human disorders elicited by disruption of redox homeostasis.

Mutagenicity and antimutagenicity of hydrophilic and lipophilic extracts of Thai northern purple rice

Purple rice (Oryza sativa L. var. indica) cv. Kum Doisaket is cultivated in northern Thailand. This study evaluated the mutagenic and antimutagenic properties of hydrophilic and lipophilic components of purple rice using the Ames test. The seed and hull of purple rice were extracted with hexane, methanol, ethanol, and water. The methanol extracts had the highest amounts of phenolic acids and flavonoids, while the hexane extracts contained large amount of tocols and γ-oryzanol. None of the extracts were mutagenic in Salmonella typhimurium strains TA98 and TA100. The hexane extract of rice hull and the methanol extract of rice seed were strongly effective against aflatoxin B1- and 2-amino-3, 4 dimethylimidazo (4, 5-f) quinoline-induced mutagenesis, while aqueous extracts showed weakly antimutagenic properties. All extracts with the exception of aqueous extracts enhanced the number of revertant colonies from benzo (a) pyrene induced-mutagenesis. None of the extracts inhibited mutagenesis induced by the direct mutagens 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide and sodium azide. The hull extracts showed more potent antimutagenicity than the seed extracts. Based on a chemical analysis, γ-oryzanol and γ-tocotrienol in the hull and cyanidin-3-glucoside and peonidin-3-glucoside in the seed are candidate antimutagens in purple rice. The antimutagenic mechanisms of purple rice might be related to either modulation of mutagen metabolizing enzymes or direct attack on electrophiles. These findings supported the use of Thai purple rice as a cancer chemopreventive agent.