Effect of dietary soybean and licorice on the male F344 rat: an integrated study of some parameters relevant to cancer chemoprevention

Antioxidative and anticancer properties of Licochalcone A from licorice

ETHNOPHARMACOLOGICAL RELEVANCE

Licochalcone A (LCA) is a characteristic chalcone that is found in licorice, which is a traditional medicinal plant. In traditional medicine, LCA possesses many potential biological activities, including anti-parasitic, anti-inflammatory and antitumor activities.

AIM OF THE STUDY

To determine the antioxidant activity of LCA and, on this basis, to investigate the role of its anticancer activity.

MATERIALS AND METHODS

To validate the antioxidant activity of LCA, the proteins SOD, CAT and GPx1 were analyzed using western blotting and cellular antioxidant activity (CAA) assays. Oxidative free radicals are associated with cancer cells. Therefore, the anticancer activity of LCA was also evaluated. To assess the anticancer activity, cell viability assays were performed and apoptosis was evaluated. In addition, MAPK-related proteins were analyzed using western blotting.

RESULTS

The experimental data showed that the EC₅₀ of LCA is 58.79±0.05μg/mL and 46.29±0.05μg/mL under the two conditions tested, with or without PBS. In addition, LCA at a concentration of approximately 2-8μg/mL can induce the expression of SOD, CAT and GPx1 proteins. Further, LCA inhibits the growth of HepG2 cells through cell proliferation arrest and the subsequent induction of apoptosis, and LCA attenuated the p38/JNK/ERK signaling pathway in a dose-dependent manner.

CONCLUSION

The results showed that LCA suppresses the oxidation of cells and markedly inhibits the proliferation of cancer cells. These findings confirm the traditional use of LCA in folk medicine.

Botanicals and Their Bioactive Phytochemicals for Women's Health

Botanical dietary supplements are increasingly popular for women's health, particularly for older women. The specific botanicals women take vary as a function of age. Younger women will use botanicals for urinary tract infections, especially Vaccinium macrocarpon (cranberry), where there is evidence for efficacy. Botanical dietary supplements for premenstrual syndrome (PMS) are less commonly used, and rigorous clinical trials have not been done. Some examples include Vitex agnus-castus (chasteberry), Angelica sinensis (dong quai), Viburnum opulus/prunifolium (cramp bark and black haw), and Zingiber officinale (ginger). Pregnant women have also used ginger for relief from nausea. Natural galactagogues for lactating women include Trigonella foenum-graecum (fenugreek) and Silybum marianum (milk thistle); however, rigorous safety and efficacy studies are lacking. Older women suffering menopausal symptoms are increasingly likely to use botanicals, especially since the Women's Health Initiative showed an increased risk for breast cancer associated with traditional hormone therapy. Serotonergic mechanisms similar to antidepressants have been proposed for Actaea/Cimicifuga racemosa (black cohosh) and Valeriana officinalis (valerian). Plant extracts with estrogenic activities for menopausal symptom relief include Glycine max (soy), Trifolium pratense (red clover), Pueraria lobata (kudzu), Humulus lupulus (hops), Glycyrrhiza species (licorice), Rheum rhaponticum (rhubarb), Vitex agnus-castus (chasteberry), Linum usitatissimum (flaxseed), Epimedium species (herba Epimedii, horny goat weed), and Medicago sativa (alfalfa). Some of the estrogenic botanicals have also been shown to have protective effects against osteoporosis. Several of these botanicals could have additional breast cancer preventive effects linked to hormonal, chemical, inflammatory, and/or epigenetic pathways. Finally, although botanicals are perceived as natural safe remedies, it is important for women and their healthcare providers to realize that they have not been rigorously tested for potential toxic effects and/or drug/botanical interactions. Understanding the mechanism of action of these supplements used for women's health will ultimately lead to standardized botanical products with higher efficacy, safety, and chemopreventive properties.

Induction of NAD(P)H:Quinone Oxidoreductase 1 (NQO1) by Glycyrrhiza Species Used for Women's Health: Differential Effects of the Michael Acceptors Isoliquiritigenin and Licochalcone A

For the alleviation of menopausal symptoms, women frequently turn to botanical dietary supplements, such as licorice and hops. In addition to estrogenic properties, these botanicals could also have chemopreventive effects. We have previously shown that hops and its Michael acceptor xanthohumol (XH) induced the chemoprevention enzyme,

NAD(P)H

quinone oxidoreductase 1 (NQO1), in vitro and in vivo. Licorice species could also induce NQO1, as they contain the Michael acceptors isoliquiritigenin (LigC) found in Glycyrrhiza glabra (GG), G. uralensis (GU), G. inflata (GI), and licochalcone A (LicA) which is only found in GI. These licorice species and hops induced NQO1 activity in murine hepatoma (Hepa1c1c7) cells; hops ≫ GI > GG ≅ GU. Similar to the known chemopreventive compounds curcumin (turmeric), sulforaphane (broccoli), and XH, LigC and LicA were active dose-dependently; sulforaphane ≫ XH > LigC > LicA ≅ curcumin ≫ liquiritigenin (LigF). Induction of the antioxidant response element luciferase in human hepatoma (HepG2-ARE-C8) cells suggested involvement of the Keap1-Nrf2 pathway. GG, GU, and LigC also induced NQO1 in nontumorigenic breast epithelial MCF-10A cells. In female Sprague-Dawley rats treated with GG and GU, LigC and LigF were detected in the liver and mammary gland. GG weakly enhanced NQO1 activity in the mammary tissue but not in the liver. Treatment with LigC alone did not induce NQO1 in vivo most likely due to its conversion to LigF, extensive metabolism, and its low bioavailability in vivo. These data show the chemopreventive potential of licorice species in vitro could be due to LigC and LicA and emphasize the importance of chemical and biological standardization of botanicals used as dietary supplements. Although the in vivo effects in the rat model after four-day treatment are minimal, it must be emphasized that menopausal women take these supplements for extended periods of time and long-term beneficial effects are quite possible.

Antioxidant activity of selected natural polyphenolic compounds from soybean via peroxyl radical scavenging

Excellent antioxidantsviaSPLET in aqueous solution, moderate antioxidantsviaHAT in lipid medium.

Increased expression of catalase in human hepatoma cells by the soy isoflavone, daidzein

The reduced incidence of cancer that has been observed in Asian population traditionally consuming soy-based food has been linked to the antioxidant potential of soy isoflavones, in particular daidzein and genistein. The present study was undertaken in order to test the antioxidative potential of daidzein and to examine the effect of daidzein treatment on the expression of the antioxidant enzyme catalase in the human hepatoma cell lines Huh-7 and HepG2. Daidzein itself did not display radical scavenging activity but it significantly increased the activity of the antioxidant enzyme catalase. Huh-7 cells were much more susceptible to daidzein cytotoxicity than HepG2 cells and showed much lower basal activity in luciferase reporter gene assays with the 3.2 kb fragment of the human catalase promoter. However, treatment with daidzein at a non-toxic concentration resulted in a similar induction of promoter activity in both cell lines. Reporter gene studies with different promoter constructs in HepG2 cells restrict the potential localization of the main regulatory elements for basal and inducible activity of the catalase promoter to a region approximately 120 bp to 300 bp upstream of the start codon of the catalase gene. From our results, we conclude that in human hepatoma cells daidzein at a non-toxic concentration increases the activity of human catalase and induces the transcription of the catalase gene via interaction with the proximal part of the promoter.

Protective effect of soybean against hepatocarcinogenesis induced by DL-ethionine

There has been increasing interest in the value of using soybean to delay or reduce the tumor incidence. This study was undertaken to investigate the possible protective effects of soybean against hepatocarcinogenesis induced by DL-ethionine. Accordingly, we measured biochemical changes occurring in serum and liver of rats treated with DL-ethionine in the presence or absence of soybean. Male albino rats were fed a control diet containing the hepatocarcinogen, DL-ethionine, or the control diet plus soybean 30%, or the control diet plus soybean plus DL-ethionine 0.25% for three months and then returned to a control diet for up to nine months. Rats fed a control diet plus DL-ethionine showed a gradual decrease in liver DNA, RNA, total protein, and liver weight and enzyme activities of liver transaminases (GOT and GPT) and alkaline phosphatase over the 7-month study period. This was followed by a large increase in the liver parameters at the end of the 9(th) month, except for 5'-nucleotidase and glucose-6-phosphatase that showed a large decrease. On the other hand, a gradual increase in the serum enzyme activities of GOT, GPT, 5-nucleotidase, alkaline phosphatase, and in the albumin/globulin (A/G) ratio is observed in the group of rats fed a control diet plus DL-ethionine compared to the control group over 8 months, and this was followed by a large increase in all serum parameters studied at nine-months. The administration of 30% soybean to the rat diet in addition to DL-ethionine maintained all parameters studied at near control values until the end of the 9(th) month. This study suggests that soybean has a protective effect against the hepatocarcinogenesis induced by DL-ethionine.

Nutritional evaluation of solar dried sardines as a ruminant protein supplement

Solar dried sardines of various qualities were analyzed for nutrient content and for nutrient digestibility and nitrogen balance in sheep. Additionally, key serum enzymes and metabolites were examined to identify potential toxic effects. Dried sardine protein, ether extract and crude ash content ranged from 65 to 39%, 5.7 to 5.1%, and 22 to 51%, respectively, for high to low quality dried sardines. Visual appraisal of the dried sardines did not appear to be very reliable for determining dried sardine quality. Crude protein content was highly correlated (r(2)=0.962) with crude ash content based on the following equation (dry matter basis): crude protein%=86.0 - (0.961xcrude ash%). Therefore, crude ash could be used to estimate crude protein content and dried sardine quality. Digestibility in Omani sheep was determined on diets composed of a composite of dried sardines collected from Al-Batinah region of the Sultanate (the average crude protein content was 51%) and compared to that of a similar diet using soybean meal (also 51% crude protein) as the major protein source. The digestibility of crude protein, ether extract, total carbohydrates, digestible energy and metabolizable energy in diets utilizing dried sardines versus the soybean meal diet were 74 versus 76%, 69 versus 68%, 67 versus 69%, 64 versus 66%, and 52 versus 56%, respectively. Although, protein digestibility was similar, nitrogen balance data suggested that nitrogen in the dried sardine diet was not as efficiently utilized as nitrogen in the soybean meal diet. Key serum enzymes and metabolites did not suggest that dried sardines at 10% of the total dietary intake would cause metabolic disturbances in sheep. The study suggests that solar dried sardines may be effectively used in ruminant diets but may not have the protein by-pass value of commercial, processed fish meals.

Inhibitory effect of glycyrrhizin on NF-kappaB binding activity in CCl4- plus ethanol-induced liver cirrhosis in rats

AIMS/BACKGROUND

Potenlini is an injectable compound whose active component is glycyrrhizin, which is extracted from licorice. Previous studies showed that it could reduce liver injury, improve alanine aminotransferase (ALT) levels and act as an antifibrotic agent. However, the mechanism of its action remains unclear. The aim of this study was to determine the molecular mechanism of its action by investigating the effects of potenlini on nuclear factor-kappaB (NF-kappaB) binding activity in an animal model of liver cirrhosis.

METHODS

Rats were randomly allocated into a normal control group, a model control group, and a potenlini group. Rats in the latter two groups were treated with CCl4 and ethanol solution in order to induce chronic liver injury. Rats in the potenlini group were given potenlini treatment at the same time.

RESULTS

Serum ALT levels were significantly reduced in rats treated with potenlini compared with levels in rats of the model control group, which had dramatically increased ALT levels. Histologically, liver steatosis and fibrosis were severe in the rats of the model group, but were significantly improved in rats of the potenlini group. NF-kappaB binding activity was markedly increased in the liver specimens taken from the rats of the model control group in comparison with the binding of normal livers, but the binding levels were nearly normal in the livers of the potenlini group.

CONCLUSIONS

The results suggest that potenlini can inhibit the NF-kappaB binding activity in CCl4 and ethanol-induced chronic liver injury, and that effect may be a possible mechanism by which potenlini protects the liver from hepatotoxin-induced liver injury and cirrhosis.

Genistein inhibits growth of B16 melanoma cells in vivo and in vitro and promotes differentiation in vitro

Consumption of soy products has been linked to a reduced mortality and morbidity from a number of cancers. Genistein, one of the principal soy isoflavones, has been shown to inhibit the growth of a number of tumour cell lines in vitro; however, a role of genistein in retarding tumour growth in vivo is less well documented. In this study, in addition to examining the effects of genistein on the growth of murine B16 melanoma cells in vitro, we have examined the effects of feeding a genistein-rich diet on s.c. growth of these tumour cells in mice. In vitro, the melanoma cells showed an increase in sensitivity to genistein with increasing time of exposure, culminating in a 50% growth inhibition (IC50) at 12.5 microM after 7 days. Genistein at 25 microM induced micronucleus formation after 24 hr and at concentrations as low as 2.5 microM induced morphological changes indicative of differentiation. Growth of solid tumours implanted into female C57BL/6J mice was inhibited by 50% when mice were fed genistein for 1 week before and for 1 week after inoculation with B16 melanoma cells. Plasma genistein concentrations at the time of tumour removal were 1.1 microM, which is similar to levels reported in humans consuming diets high in soybeans or soybean products, while control animals had no detectable genistein in plasma. Our results provide additional in vivo evidence suggesting that genistein retards the growth of implanted tumours, adding further to studies suggesting that this isoflavonoid is a biologically active component of soy foods.

High-performance liquid chromatographic assay of isoflavonoids and coumestrol from human urine

A rapid, sensitive and precise diode-array reversed-phase HPLC method was developed for human urine analysis of the most common dietary isoflavones daidzein, genistein, formononetin and biochanin-A, their mammalian metabolites equol and O-desmethylangolensin, and of coumestrol, another commonly occurring phytoestrogen. Analytes were isolated and concentrated by solid-phase extraction and separated by HPLC followed by identification through retention times and UV scans, and in the case of coumestrol additionally by fluorometric response. This method was applied to monitor changes in urinary excretion of these analytes after challenge with soybeans and was evaluated for precision and recovery of analytes.