Estrogenic activities of Ginkgo biloba extracts

Estrogenic flavonoids and their molecular mechanisms of action

Flavonoids are a major group of phytoestrogens associated with physiological effects, and ecological and social impacts. Although the estrogenic activity of flavonoids was reported by researchers in the fields of medical, environmental and food studies, their molecular mechanisms of action have not been comprehensively reviewed. The estrogenic activity of the respective classes of flavonoids, anthocyanidins/anthocyanins, 2-arylbenzofurans/3-arylcoumarins/α-methyldeoxybenzoins, aurones/chalcones/dihydrochalcones, coumaronochromones, coumestans, flavans/flavan-3-ols/flavan-4-ols, flavanones/dihydroflavonols, flavones/flavonols, homoisoflavonoids, isoflavans, isoflavanones, isoflavenes, isoflavones, neoflavonoids, oligoflavonoids, pterocarpans/pterocarpenes, and rotenone/rotenoids, was summarized through a comprehensive literature search, and their structure-activity relationship, biological activities, signaling pathways, and applications were discussed. Although the respective classes of flavonoids contained at least one chemical mimicking estrogen, the mechanisms varied, such as those with estrogenic, anti-estrogenic, non-estrogenic, and biphasic activities, and additional activities through crosstalk/bypassing, which exert biological activities through cell signaling pathways. Such mechanistic variations of estrogen action are not limited to flavonoids and are observed among other broad categories of chemicals, thus this group of chemicals can be termed as the "estrogenome". This review article focuses on the connection of estrogen action mainly between the outer and the inner environments, which represent variations of chemicals and biological activities/signaling pathways, respectively, and form the basis to understand their applications. The applications of chemicals will markedly progress due to emerging technologies, such as artificial intelligence for precision medicine, which is also true of the study of the estrogenome including estrogenic flavonoids.

Pomegranate juice fermented by tannin acyl hydrolase and Lactobacillus vespulae DCY75 enhance estrogen receptor expression and anti-inflammatory effect

Phenolics are phytochemicals in plants, fruits, and vegetables have potential health-promoting efficacies. However, mostly available as a complex form. So, to increase the contents and nutritional value of the phenolic compounds, fermentation is most readily used in the food industry. Especially, the hydrolyzable tannins present in the pomegranate that can be liberated into monomolecular substances, which enhances biological activity. Thus, this study aims to convert hydrolyzable tannins to ellagic acid by fermentation using Tannin acyl hydrolase (TAH) and a novel bacteria strain Lactobacillus vespulae DCY75, respectively to investigate its effect on Estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) mRNA expression along with inflammation inhibition. As a result, the fermentation enhanced the ellagic acid content up to 70% by the synergetic effect of TAH and DCY75. Furthermore, fermented pomegranate (PG-F) increased cellular proliferation as well as upregulated the gene expression of estrogen regulators such as ERα, ERβ, and pS2 in breast cancer cell line (MCF-7), which commonly used to evaluate estrogenic activity. Moreover, to study the inflammation associated with low estrogen in menopause, we have analyzed the inhibition of nitric oxide (NO)/inducible nitric oxide synthase (iNOS) in RAW 264.7 cells. The PG-F juice did not exert any cytotoxicity in RAW 264.7 cells and inhibited NO production along with the downregulation of a major pro-inflammatory cytokine iNOS which indicates the anti-inflammatory potential of it. To sum it up, the fermented commercial pomegranate juice using a novel bacteria strain increased the amount of ellagic acid that the value added bioactive of pomegranate and it has significantly increased the estrogenic activity via upregulating estrogen related biomarkers expression and reduced the risk of related inflammation via NO/iNOS inhibition. This study could be a preliminary study to use fermented pomegranate as a potential health functional food after further evaluation.

Ginkgo biloba attenuates aluminum lactate-induced neurotoxicity in reproductive senescent female rats: behavioral, biochemical, and histopathological study

Extensive use of aluminum (Al) in industry, cooking utensils, and wrapping or freezing the food items, due to its cheapness and abundance in the environment, has become a major concern. Growing evidence supports that environmental pollutant Al promotes the aggregation of amyloid beta (Aβ) in the brain, which is the main pathological marker of Alzheimer's disease (AD). Further, AD- and Al-induced neurotoxic effects are more common among women following reproductive senescence due to decline in estrogen. Though clinically Ginkgo biloba extract (GBE) has been exploited as a memory enhancer, its role in Al-induced neurotoxicity in reproductive senescent female rats needs to be evaluated. Animals were exposed to intraperitoneal dose (10 mg/kg b.wt) of Al and oral dose (100 mg/kg b.wt.) of GBE daily for 6 weeks. A significant decline in the Al-induced Aβ aggregates was observed in hippocampal and cortical regions of the brain with GBE supplementation, as confirmed by thioflavin (ThT) and Congo red staining. GBE administration significantly decreased the reactive oxygen species, lipid peroxidation, nitric oxide, and citrulline levels in comparison to Al-treated rats. On the contrary, a significant increase in the reduced glutathione, GSH/GSSG ratio as well as in the activities of antioxidant enzymes was observed with GBE administration. Based on the above results, GBE prevented the neuronal loss in the hippocampus and cortex, hence caused significant improvement in the learning and memory of the animals in terms of AChE activity, serotonin levels, Morris water maze, and active and passive avoidance tests. In conclusion, GBE has alleviated the behavioral, biochemical, and histopathological alterations due to Al toxicity in rats. However, molecular studies are going on to better understand the mechanism of GBE protection against the environmental toxicant Al exposure. Graphical abstract .

Chinese Medicines Improve Perimenopausal Symptoms Induced by Surgery, Chemoradiotherapy, or Endocrine Treatment for Breast Cancer

The application of surgery, chemoradiotherapy, and endocrine treatment successfully increases survival rates of breast cancer patients. However, perimenopausal symptoms, the main side effects of these treatments, often afflict patients and reduce their quality of life. Perimenopausal symptoms include vasomotor symptoms, sleep problems, arthromuscular symptoms, and osteoporosis. Currently, there are no satisfactory treatments for perimenopausal symptoms that result from these treatments. Therefore, alternative and complementary therapies including herbal medicines represented by Chinese medicines (CMs), acupuncture, massage, and psychotherapy are increasingly being expected and explored. In this paper, we review the effects and potentials of several CM formulae, along with some active ingredients or fractions from CMs, Chinese herbal extracts, and other herbal medicines, which have drawn attention for improving perimenopausal symptoms in breast cancer patients. We also elaborate their possible mechanisms. Moreover, further studies for evaluation of standardized clinical efficacy should be scientifically well-designed and continuously performed to investigate the efficacy and mechanisms of CMs for perimenopausal symptoms due to breast cancer therapy. The safety and value of estrogen-containing CMs for breast cancer should also be clarified.

Ginkgo biloba extract (EGb761) did not express estrogenic activity in an immature rat uterotrophic assay

Ginkgo biloba is a dioecious tree that has been used in traditional Chinese medicine for about 5,000 years. In previous studies on ginkgo biloba extract (EGb761) using in vitro systems, we confirmed that EGb761 has biphasic effects on estrogenicity. In this study, we evaluated the agonistic and antagonistic activities of EGb761 using a uterotrophic assay in immature female rats. To evaluate agonistic and antagonistic effects of EGb761 on uterus, 21-day-old immature Sprague-Dawley (SD) female rats were treated with EGb761 (100, 200, or 400 mg/kg) by oral gavage, 10 μg/kg of estradiol (E2) or 1 mg/kg tamoxifen (TM) by subcutaneous injection, or with EGb761 plus E2 or TM for 3 consecutive days. At the end of the treatment period, animals were sacrificed and their body weights and organ weights (liver, lung, spleen and kidney) were measured. In addition, estrogen-related gene expressions (IGFBP-1 in liver and CaBP-9 in uterus) were determined. During the experiment, no animal showed clinical signs, a change in body weight or died. EGb761 treatment alone had no effect on absolute/relative uterine weight, luminal epithelial cell height (LECH, μm), or luminal circumference (LC, μm). In addition, uterine weights, LECHs, and LC induced by E2 or TM were not significantly changed by EGb761 at any dose. These results collectively suggested EGb761 has no agonistic/antagonistic effects in utero.

Quercetin improves postpartum hypogalactia in milk-deficient mice via stimulating prolactin production in pituitary gland

Postpartum dysgalactia is a common clinical problem for lactating women. Seeking out the safe and efficient phytoestrogens will be a promising strategy for postpartum dysgalactia therapy. In this study, the postpartum mice within four groups, including control group, the model group, and the treatment groups intragastrically administrated with normal saline, bromocriptine, bromocriptine plus 17α-ethinyl estradiol, and bromocriptine plus quercetin, respectively, were used. The results showed that quercetin, a kind of natural phytoestrogen, could efficiently promote lactation yield and mammary gland development in the agalactosis mice produced by bromocriptine administration. Mechanically, quercetin, such as 17α-ethinyl estradiol, significantly stimulated prolactin (PRL) production and deposition in the mammary gland in the agalactosis mice determined by western blotting, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay, respectively. Furthermore, quercetin could increase the expression of β-casein, stearoyl-CoA desaturase, fatty acid synthase, and α-lactalbumin in the breast tissues that are responsible for the production of fatty acid, lactose, and galactose in the milk at the transcriptional level determined by quantitative polymerase chain reaction. Specifically, quercetin promoted primary mammary epithelial cell proliferation and stimulated prolactin receptor (PRLR) expression probably via AKT activation in vitro. In conclusion, this study indicates that estrogen-like quercetin promotes mammary gland development and lactation yield in milk-deficient mice, probably via stimulating PRL expression and release from the pituitary gland, as well as induces PRLR expression in primary mammary epithelial cells.

Evaluation of the anti-osteoporotic effect of Ginkgo biloba L. in Wistar rats with glucocorticoid-induced-osteoporosis by bone densitometry using dual-energy x-ray absorptiometry (DEXA) and mechanical testing

Evaluate the effect of the extract of Ginkgo biloba in the bone alkaline phosphatase, bone mineral density, in the mechanical properties of the tibia in rats with glucocorticoid-induced-osteoporosis. After osteoporosis induction, the rats were divided into five groups: Osteoporosis; EGb1 (28 mg/Kg); EGb2 (56 mg/Kg); alendronate (0.2 mg/animal) and control. The animals were treated during 20 and 30 days. The control group was compared with the osteoporosis's (Student's t-test), while the other were analyzed by ANOVA test followed by Tukey/Dunnett'T3 (p<0.05). In the osteoporosis group the bone alkaline phosphatase, bone mineral density, the bone stiffness, the maximum load and the resilience were reduced. The bone alkaline phosphatase values increased in the EGb1 and EGb2 groups (30 days). In addition, in the EGb2 and alendronate groups (20 and 30 days) the bone mineral density increased. The extract of Ginkgo biloba restored bone alkaline phosphatase and bone mineral density using dual-energy x-ray absorptiometry.

Ginkgo biloba Extract (GbE) Stimulates the Hypothalamic Serotonergic System and Attenuates Obesity in Ovariectomized Rats

Menopause is associated with increased risk to develop obesity but the mechanisms involved are not fully understood. We have shown that Ginkgo biloba extract (GbE) improved diet-induced obesity. Since GbE might be effective in the treatment of obesity related to menopause, avoiding the side effects of hormone replacement therapy, we investigated the effect of GbE on hypothalamic systems controlling energy homeostasis. Wistar rats were either ovariectomized (OVX) or Sham-operated. After 2 months, either 500 mg.kg^-1 of GbE or vehicle were administered daily by gavage for 14 days. A subset of animals received an intracerebroventricular (i.c.v.) injection of serotonin (300 μg) or vehicle and food intake was measured after 12 and 24 h. Another subset was submitted to in vivo microdialysis and 5-HT levels of the medial hypothalamus were measured by high performance liquid chromatography, before and up to 2 h after the administration of 500 mg.kg^-1 of GbE. Additional animals were used for quantification of 5-HT_1A, 5-HT_1B, 5-HT_2C, 5-HTT, and pro-opiomelanocortin hypothalamic protein levels by Western blotting. OVX increased food intake and body weight and adiposity while GbE attenuated these alterations. i.c.v. serotonin significantly reduced food intake in Sham, Sham + GbE, and OVX + GbE groups while it failed to do so in the OVX group. In the OVX rats, GbE stimulated 5-HT microdialysate levels while it reduced hypothalamic 5-HTT protein levels. The results indicate that GbE improved the ovariectomy-induced resistance to serotonin hypophagia, at least in part through stimulation of the hypothalamic serotonergic activity. Since body weight gain is one of the most important consequences of menopause, the stimulation of the serotonergic transmission by GbE may represent a potential alternative therapy for menopause-related obesity.

Ethanolic extract of dandelion (Taraxacum mongolicum) induces estrogenic activity in MCF-7 cells and immature rats

Plants of the genus Taraxacum, commonly known as dandelions, are used to treat breast cancer in traditional folk medicine. However, their use has mainly been based on empirical findings without sufficient scientific evidence. Therefore, we hypothesized that dandelions would behave as a Selective estrogen receptor modulator (SERM) and be effective as hormone replacement therapy (HRT) in the postmenopausal women. In the present study, in vitro assay systems, including cell proliferation assay, reporter gene assay, and RT-PCR to evaluate the mRNA expression of estrogen-related genes (pS2 and progesterone receptor, PR), were performed in human breast cancer cells. Dandelion ethanol extract (DEE) significantly increased cell proliferation and estrogen response element (ERE)-driven luciferase activity. DEE significantly induced the expression of estrogen related genes such as pS2 and PR, which was inhibited by tamoxifen at 1 μmol·L(-1). These results indicated that DEE could induce estrogenic activities mediated by a classical estrogen receptor pathway. In addition, immature rat uterotrophic assay was carried out to identify estrogenic activity of DEE in vivo. The lowest concentration of DEE slightly increased the uterine wet weight, but there was no significant effect with the highest concentration of DEE. The results demonstrate the potential estrogenic activities of DEE, providing scientific evidence supporting their use in traditional medicine.

The effects of the standardized extracts of Ginkgo biloba on steroidogenesis pathways and aromatase activity in H295R human adrenocortical carcinoma cells

OBJECTIVES

Aromatase inhibitors that block estrogen synthesis are a proven first-line hormonal therapy for postmenopausal breast cancer. Although it is known that standardized extract of Ginkgo biloba (EGb761) induces anti-carcinogenic effects like the aromatase inhibitors, the effects of EGb761 on steroidogenesis have not been studied yet. Therefore, the effects of EGb761 on steroidogenesis and aromatase activity was studied using a H295R cell model, which was a good in vitro model to predict effects on human adrenal steroidogenesis.

METHODS

Cortisol, aldosterone, testosterone, and 17β-estradiol were evaluated in the H295R cells by competitive enzyme-linked immunospecific assay after exposure to EGb761. Real-time polymerase chain reaction were performed to evaluate effects on critical genes in steroid hormone production, specifically cytochrome P450 (CYP11/ 17/19/21) and the hydroxysteroid dehydrogenases (3β-HSD2 and 17β-HSD1/4). Finally, aromatase activities were measured with a tritiated water-release assay and by western blotting analysis.

RESULTS

H295R cells exposed to EGb761 (10 and 100 μg/mL) showed a significant decrease in 17β-estradiol and testosterone, but no change in aldosterone or cortisol. Genes (CYP19 and 17β-HSD1) related to the estrogen steroidogenesis were significantly decreased by EGb761. EGb761 treatment of H295R cells resulted in a significant decrease of aromatase activity as measured by the direct and indirect assays. The coding sequence/ Exon PII of CYP19 gene transcript and protein level of CYP19 were significantly decreased by EGb761.

CONCLUSIONS

These results suggest that EGb761 could regulate steroidogenesis-related genes such as CYP19 and 17β-HSD1, and lead to a decrease in 17β-estradiol and testosterone. The present study provides good information on potential therapeutic effects of EGb761 on estrogen dependent breast cancer.

Evaluation of the Biological Activity of Opuntia ficus indica as a Tissue- and Estrogen Receptor Subtype-Selective Modulator

Phytoestrogens are selective estrogen receptor modulators (SERMs) with potential for use in hormone replacement therapy (HRT) to relieve peri/postmenopausal symptoms. This study was aimed at elucidating the molecular mechanisms underlying the SERM properties of the extract of Korean-grown Opuntia ficus-indica (KOFI). The KOFI extract induced estrogen response element (ERE)-driven transcription in breast and endometrial cancer cell lines and the expression of endogenous estrogen-responsive genes in breast cancer cells. The flavonoid content of different KOFI preparations affected ERE-luciferase activities, implying that the flavonoid composition likely mediated the estrogenic activities in cells. Oral administration of KOFI decreased the weight gain and levels of both serum glucose and triglyceride in ovariectomized (OVX) rats. Finally, KOFI had an inhibitory effect on the 17β-estradiol-induced proliferation of the endometrial epithelium in OVX rats. Our data demonstrate that KOFI exhibited SERM activity with no uterotrophic side effects. Therefore, KOFI alone or in combination with other botanical supplements, vitamins, or minerals may be an effective and safe alternative active ingredient to HRTs, for the management of postmenopausal symptoms. Copyright © 2016 John Wiley & Sons, Ltd.

Estrogenic endocrine disruptors: Molecular mechanisms of action

A comprehensive summary of more than 450 estrogenic chemicals including estrogenic endocrine disruptors is provided here to understand the complex and profound impact of estrogen action. First, estrogenic chemicals are categorized by structure as well as their applications, usage and effects. Second, estrogenic signaling is examined by the molecular mechanism based on the receptors, signaling pathways, crosstalk/bypassing and autocrine/paracrine/homeostatic networks involved in the signaling. Third, evaluation of estrogen action is discussed by focusing on the technologies and protocols of the assays for assessing estrogenicity. Understanding the molecular mechanisms of estrogen action is important to assess the action of endocrine disruptors and will be used for risk management based on pathway-based toxicity testing.

Assessment of hormone-like activities in Ginkgo biloba, Elettaria cardamomum and Plantago ovata extracts using in vitro receptor-specific bioassays

Medicinal plants are widely used for the treatment of diseases and for the development of new drugs. This study was designed to determine the presence of hormone-like activities dependent on the activation of human estrogen receptor alpha (hERa) and/or androgen receptor (hAR) in methanol extracts prepared from three medicinal plants historically and currently used for therapeutic purposes: Ginkgo biloba leaves (GBL), Elettaria cardamomum seeds (ECS) and Plantago ovata seeds (POS). After a solid-liquid extraction (SLE) step, their effects on hERa function were assessed in MCF-7 breast cancer cells using the E-Screen bioassay, and their ability to induce hAR-mediated reporter gene expression was evaluated using the androgen-sensitive stable prostatic PALM cell line. Unlike POS extracts, GBL and ECS extracts showed estrogenic (0.07 and 0.20 nM E2Eq mg(-1), respectively) and anti-estrogenic (0.01 and 0.02 μM ICI182780Eq mg(-1), respectively) activities. ECS extracts evidenced androgenic activity (0.30 nM R1881Eq mg(-1)) and POS extracts anti-androgenic activity (22.30 μM ProcEq mg(-1)). According to these findings, these plant extracts may interfere with the endocrine system via one or more hormonal receptors, and further investigation is warranted into their role as endocrine disrupters in humans.

A molecular docking study of phytochemical estrogen mimics from dietary herbal supplements

PURPOSE

The purpose of this study is to use a molecular docking approach to identify potential estrogen mimics or anti-estrogens in phytochemicals found in popular dietary herbal supplements.

METHODS

In this study, 568 phytochemicals found in 17 of the most popular herbal supplements sold in the United States were built and docked with two isoforms of the estrogen receptor, ERα and ERβ (a total of 27 different protein crystal structures).

RESULTS

The docking results revealed six strongly docking compounds in Echinacea, three from milk thistle (Silybum marianum), three from Gingko biloba, one from Sambucus nigra, none from maca (Lepidium meyenii), five from chaste tree (Vitex agnus-castus), two from fenugreek (Trigonella foenum-graecum), and two from Rhodiola rosea. Notably, of the most popular herbal supplements for women, there were numerous compounds that docked strongly with the estrogen receptor: Licorice (Glycyrrhiza glabra) had a total of 26 compounds strongly docking to the estrogen receptor, 15 with wild yam (Dioscorea villosa), 11 from black cohosh (Actaea racemosa), eight from muira puama (Ptychopetalum olacoides or P. uncinatum), eight from red clover (Trifolium pratense), three from damiana (Turnera aphrodisiaca or T. diffusa), and three from dong quai (Angelica sinensis). Of possible concern were the compounds from men's herbal supplements that exhibited strong docking to the estrogen receptor: Gingko biloba had three compounds, gotu kola (Centella asiatica) had two, muira puama (Ptychopetalum olacoides or P. uncinatum) had eight, and Tribulus terrestris had six compounds.

CONCLUSIONS

This molecular docking study has revealed that almost all popular herbal supplements contain phytochemical components that may bind to the human estrogen receptor and exhibit selective estrogen receptor modulation. As such, these herbal supplements may cause unwanted side effects related to estrogenic activity.

Antiproliferative effect of the Ginkgo biloba extract is associated with the enhancement of cytochrome P450 1B1 expression in estrogen receptor-negative breast cancer cells

Ginkgo biloba is a dioecious tree and its extract is a complex mixture that has been used for thousands of years to treat a variety of ailments in traditional Chinese medicine. The aim of this study was to present our observations on the inhibitory effects of different Ginkgo biloba extracts on human breast cancer cell proliferation and growth. Our results demonstrated that treatment of MCF-7 and MDA-MB-231 human breast cancer cells with Ginkgo biloba leaves and ginkgo fruit extract inhibited cell proliferation. It was also observed that this inhibition was accompanied by the enhancement of cytochrome P450 (CYP) 1B1 expression in MDA-MB-231 cells. In addition, treatment with ginkgo fruit extract resulted in a higher CYP1B1 expression in MDA-MB-231 cells compared to treatment with the Ginkgo biloba leaves extract. Our results suggested that the inhibitory effects of the Ginkgo biloba extract on estrogen receptor-negative breast cancer proliferation and the induction of CYP1B1 expression may be exerted through an alternative pathway, independent of the estrogen receptor or the aryl hydrocarbon receptor pathway.

Chemopreventive effects of Ginkgo biloba extract in estrogen-negative human breast cancer cells

Excessive level of estrogen is considered as a main cause of breast cancer, therefore, many studies have focused on estrogen receptor (ER)-positive breast cancer, even though ER-negative cancer has a poor prognosis than ER-positive breast cancer. We evaluated the anti-cancer effects of Ginkgo biloba extract (GBE) in estrogen-independent breast cancer. GBE has been traditionally used as a platelet activating factor, a circulatory stimulant, a tonic, and anti-asthmatic drug, and anti-cancer agent. However, anti-cancer effects of GBE on ER-negative breast cancer have not been proved yet. In this study, we tested chemotherapeutic potential of GBE in the MDA-MB-231 (ER-negative) human breast cancer cell line. Our results showed that cytotoxicity effects of GBE in MDA-MB-231 lead to DNA fragmentation at high concentrations (500 and 1,000 μg/ml). Caspase-3 was significantly activated and mRNA levels of apoptosis-related genes (Bcl-2 and Bax) were altered. These results indicate that GBE induces apoptosis in MDA-MB-231 cells. It is presumed that GBE has chemopreventive effects in ER-independent breast cancer through anti-proliferation and apoptosis-inducing activities.

Effects of Ginkgo biloba on chemically-induced mammary tumors in rats receiving tamoxifen

Background

Ginkgo biloba extract (GbE) is used extensively by breast cancer patients undergoing treatment with Tamoxifen (TAM). Thus, the present study investigated the effects of GbE in female Sprague–Dawley (SD) rats bearing chemically-induced mammary tumors and receiving TAM.

Methods

Animals bearing mammary tumors (≥1 cm in diameter) were divided into four groups: TAM [10 mg/kg, intragastrically (i.g.)], TAM plus GbE [50 and 100 mg/kg, intraperitoneally (i.p.)] or an untreated control group. After 4 weeks, the therapeutic efficacy of the different treatments was evaluated by measuring the tumor volume (cm³) and the proportions of each tumor that were alive, necrotic or degenerative (mm²). In addition, labeling indexes (LI%) were calculated for cell proliferation (PCNA LI%) and apoptosis (cleaved caspase-3 LI%), expression of estrogen receptor-alpha (ER-α) and p63 biomarkers.

Results

Overall, the tumor volume and the PCNA LI% within live tumor areas were reduced by 83% and 99%, respectively, in all TAM-treated groups when compared to the untreated control group. GbE treatment (100 mg/kg) reduced the proportions of live (24.8%) and necrotic areas (2.9%) (p = 0.046 and p = 0.038, respectively) and significantly increased the proportion of degenerative areas (72.9%) (p = 0.004) in mammary tumors when compared to the group treated only with TAM. The expression of ER-α, p63 and cleaved caspase-3 in live tumor tissues was not modified by GbE treatment.

Conclusions

Co-treatment with 100 mg/kg GbE presented a slightly beneficial effect on the therapeutic efficacy of TAM in female SD rats bearing mammary tumors.

Investigation of herb-drug interactions with ginkgo biloba in women receiving hormonal treatment for early breast cancer

Women receiving treatment for breast cancer commonly ingest herbal medicines. Little is known about the potential for herb-drug interactions in this population. The aim of this study is to investigate the effect of ginkgo biloba co-administration on the pharmacokinetics of tamoxifen, anastrozole and letrozole. This was a prospective open-label cross-over study in 60 women with early stage breast cancer taking either tamoxifen, anastrozole or letrozole (n=20/group). Participants received ginkgo biloba (EGb 761) for 3 weeks (120 mg twice daily). Trough concentrations of drugs were measured before and after ginkgo biloba treatment using LC-MS/MS. Toxicities were graded according to National Cancer Institute Common Terminology Criteria for Adverse Events. Trough concentrations before and after treatment with ginkgo biloba were not significantly different for tamoxifen (93.5 ± 29.0, 86.5 ± 25.3 ng/mL; p=0.16), letrozole (91.1 ± 50.4, 89.6 ± 52.14 ng/mL; p=0.60) or anastrozole (29.1 ± 8.6, 29.1 ± 7.6 ng/mL; p=0.97). Ginkgo biloba was well tolerated, with no difference in toxicity during ginkgo biloba. Co-administration of ginkgo biloba does not significantly affect the pharmacokinetics of tamoxifen, anastrozole or letrozole. There was no difference in the toxicity profile of hormone therapy with ginkgo biloba use in women with early stage breast cancer.

The Aryl Hydrocarbon Receptor: A Target for Breast Cancer Therapy

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates a battery of genes in response to exposure to a broad class of environmental poly aromatic hydrocarbons (PAH). AhR is historically characterized for its role in mediating the toxicity and adaptive responses to these chemicals, however mounting evidence has established a role for it in ligand-independent physiological processes and pathological conditions, including cancer. The AhR is overexpressed and constitutively activated in advanced breast cancer cases and was shown to drive the progression of breast cancer. In this article we will review the current state of knowledge on the possible role of AhR in breast cancer and how it will be exploited in targeting AhR for breast cancer therapy.

Protective effects of Ginkgo biloba extract on ligature-induced periodontitis in rats

OBJECTIVE

The aim of this study was to test the hypothesis that the systemic administration of extract of Ginkgo biloba (EGb) would prevent excessive tissue destruction in ligature-induced periodontitis in a rat model.

MATERIALS AND METHODS

Thirty-two male Wistar albino rats were used in the current study. The rats were randomly divided into four groups of eight rats each: (1) non-ligated treatment (NL) group, (2) ligature-only (LO) group, (3) ligature plus GB28 (28 mg/kg, daily for 11 days) group and (4) ligature plus GB56 (56 mg/kg, daily for 11 days) group.

RESULTS

Measurement of alveolar bone loss in the mandibular molar tooth revealed significantly lower bone loss values in the LO group compared to groups NL, GB28 and GB56 (p < 0.05).

CONCLUSION

The present results are the first data which suggests that host response in periodontitis can be modified by EGb administration. EGb minimized progression of periodontal disease.

Estrogenic effects and their action mechanism of the major active components of party pill drugs

Benzylpiperazine (BZP) and trifluoromethylphenylpiperazine (TFMPP) are commonly used constituents of party pill drugs. They are reported to induce psychoactive effects such as euphoria and provide effects similar with other illicit drugs such as methylenedioxymethamphetamine (MDMA). A great deal of evidence has proven that party pills, as alternatives for MDMA, exert harmful effects on users. However, their toxicological effects have not been fully understood and endocrine disruptive effects are still unknown. In this study, we identified estrogenic effects of BZP and TFMPP by using in vitro and in vivo assays. BZP and TFMPP stimulated cell proliferation in a dose-dependent manner, while co-treatment with tamoxifen and BZP or TFMPP showed a decrease of E(2)-induced cell proliferation. In an estrogen sensitive reporter gene assay, BZP and TFMPP significantly increased transcriptional activities of party pill drugs. In addition, ER-related genes, PR and pS2, were significantly stimulated by BZP and TFMPP. These results indicated that BZP and TFMPP could have estrogenic activities related to the ER-mediated pathway. Unlike the in vitro assay results, BZP and TFMPP did not show significant effects on weight increase in a rodent uterotrophic assay. However, further studies would be necessary to verify the estrogenic activities of BZP and TFMPP by a chronic exposure animal study.

Antiosteoporotic compounds from seeds of Cuscuta chinensis

ETHNOPHARMACOLOGICAL RELEVANCE

The seeds of Cuscuta chinensis (Tu-Si-Zi, TSZ) have long been used for the treatment of osteoporosis in China and some Asian countries. The compounds in TSZ responsible for the antiosteoporotic activity are still poorly understood.

AIM OF THE STUDY

The present study was designed to investigate the osteogenic compounds in TSZ, and to evaluate their antiosteoporotic effects in osteoblastic cells.

MATERIALS AND METHODS

Osteoblast-like UMR-106 cells were used for bioactivity-guided isolation of the active compounds. The activity of alkaline phosphatase (ALP) in UMR-106 cells was measured by p-nitrophenyl sodium phosphate assay. The proliferation of UMR-106 cells was assayed by Alamar-Blue method. Estrogenic activity of the extracts and isolated compounds was evaluated by activation of estrogen response element (ERE) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 5×ERE luciferase reporter plasmid. Antiestrogenic activity of the extracts and isolated compounds were evaluated by activation of activator protein-1 (AP-1) luciferase reporter expression in HeLa cells co-transfected with human estrogen receptor subtypes (ERα or ERβ) expression vectors and 6×AP-1 luciferase reporter plasmid.

RESULTS

ALP-guided fractionation led to the isolation of five known flavonoids, quercetin, kaempferol, isorhamnetin, hyperoside and astragalin from the crude ethanolic extract of TSZ. Further study showed that kaempferol and hyperoside significantly increased the ALP activity in UMR-106 cells. Astragalin promoted the proliferation of UMR-106 cells whereas other compounds had no such effect. The isolated compounds showed estrogenic activity but quercetin, kaempferol and isorhamnetin showed more potent ERβ agonist activity. However, compared with their ER agonist activity, only quercetin and kaempferol showed potent ER antagonist activity by activating ERα/β-mediated AP-1 reporter expression.

CONCLUSIONS

Our findings validated the clinical use of TSZ in the treatment of osteoporosis, and demonstrated that kaempferol and hyperoside are the active compounds in TSZ for the osteogenic effect.

Effects of Ginkgo biloba extract on the embryo-fetal development in Wistar rats

BACKGROUND

Ginkgo biloba extract (GBE) is an herbal medicine used for treating neurodegenerative diseases, cerebrovascular insufficiency, peripheral arterial occlusive disease, and also vestibular disturbance. Some components of GBE have presented estrogenic effects and, in a previous study, high dosages of GBE caused intra-uterine growth retardation in fetuses of Wistar rats treated during the fetogenesis period.

METHODS

Pregnant Wistar rats were treated, through gavage, with different dosages of aqueous GBE (3.5, 7.0, and 14.0 mg/Kg/day), during the tubal transit and implantation period. Rats were killed on the 15th day of pregnancy and the following parameters were evaluated: clinical symptoms of maternal toxicity; maternal body weight; feed and water intake; maternal liver, kidney, and ovary weights; number of corpora lutea; implants per group ratio; pre- and post-implantation loss per group ratio; live fetuses mean; dead fetuses percentage; fetus and placenta weight per offspring ratio; and fetal external malformation.

RESULTS

No significant alteration was found for both the maternal and embryonic parameters evaluated.

CONCLUSIONS

The GBE treatment in pregnant Wistar rats, during the tubal transit and implantation period, caused no toxic effect on the maternal organism and did not induce embryonic death, growth retardation, and/or fetal malformations.

Evidences of osteoporosis improvement in Wistar rats treated with Ginkgo biloba extract: a histomorphometric study of mandible and femur

This study was aimed at investigating the anti-osteoporotic effects of the extract of Ginkgo biloba (EGb) in glucocorticoid-induced-osteoporosis. A significant reduction was observed in the percentage of the bone of the osteoporosis group in both the mandible and femur. The EGb group treated with 28 and 56 mg/Kg showed a significant increase in the percentage of trabecular bone (PTB) of the femur. The percentage of the alveolar bone of the mandible (PAB) had a significant increase with all doses of EGb. The treatment with EGb significantly reversed the loss of the PAB of the mandible and of the PTB of the femur.

Involvement of P-glycoprotein in regulating cellular levels of Ginkgo flavonols: quercetin, kaempferol, and isorhamnetin

Quercetin, kaempferol, and isorhamnetin were the most important flavonoid constituents in extracts from Ginkgo biloba leaves. Transport studies of Ginkgo flavonols were performed in Caco-2 cell mono-layers. Their apparent permeability in absorptive and secretion directions was determined, and quercetin, kaempferol and isorhamnetin displayed polarized transport, with the Papp,B-A being higher than the Papp,A-B (P &lt; 0.01 for quercetin, P &lt; 0.001 for kaempferol and isorhamnetin, Student's t-test). Bcap37/MDR1 cells, which were transfected with a P-glycoprotein (P-gp) gene construct, were treated with quercetin, kaempferol or isorhamnetin. The concentrations of Ginkgo flavonol in Bcap37/MDR1 cells were lower than those in parent cells (P &lt; 0.05 for quercetin, P &lt; 0.01 for isorhamnetin, Mann-Whitney U test). The concentrations of the flavonol in transfected cells increased when incubated with the P-gp inhibitor verapamil (P &lt; 0.05 for kaempferol, Mann-Whitney U test). A colorometric assay for ATPase activity was applied to the detection of interaction of flavonol with P-gp. Quercetin and kaempferol inhibited the ATPase activity, and isorhamnetin stimulated the ATPase activity (P &lt; 0.05 for isorhamnetin, Mann Whitney U test). The results indicated that Ginkgo flavonols quercetin, kaempferol and isorhamnetin were substrates of P-gp. The P-gp type efflux pump might limit the bioavailability of Ginkgo flavonols.

Intra-herb pharmacokinetics interaction between quercetin and isorhamentin

AIM

Quercetin and isorhamnetin are common constituents of some herb extracts, such as extracts of gingko leaves and total flavones of Hippophae rhamnoides L. The intra-herb pharmacokinetics interactions between isorhamnetin and quercetin were investigated in the present study.

METHODS

Human MDR1 cDNA transfected MDCKII cells were used to validate whether isorhamnein interacted with P-gp. Caco-2 transport assays and a randomized, 3-way crossover pharmacokinetics study in rats were used to investigate the pharmacokinetics interactions. HPLC was used to determine cell transport samples. The total plasma concentrations of quercetinand isorhamnetin were determined by liquid chromatography tandem mass spectrometry (LC-MS/MS) by treatment with beta-glucuronidase and sulfatase.

RESULTS

The permeability ratio (absorptive permeability/secretive permeability) of isorhamnetin across human MDR1 cDNA transfected MDCKII cells, Caco-2 cells and wild-type MDCKII cells are 0.25+/-0.02, 0.74+/-0.05, and 1.41+/-0.06, respectively. This result proved the role of P-gp in the cell efflux of isorhamnetin. While co-transporting with each other across Caco-2 cells monolayer, the permeability ratio of isorhamnetin and quercetin increased by 4.3 and 2.2 times. After coadministration with each other to rats, the C(max), AUC(0-72 h), and AUC(0-infinity) of both isorhamnetin and quercetin significantly increased compared with single administration.

CONCLUSION

The above results proved intra-herb pharmacokinetics interaction between quercetin and isorhamentin. P-gp might play an important role, whereas other drug efflux pumps, such as multi-drug resistance associate protein 2 and breast cancer resistance protein, might be involved. Accordingly, besides the drug-herb interactions, intra-herb interaction might be brought into view with the wide use of herbal-based remedies.

South African herbal teas: Aspalathus linearis, Cyclopia spp. and Athrixia phylicoides--a review

Rooibos (Aspalathus linearis (Brum.f) Dahlg.) and honeybush (Cyclopia Vent. species) are popular indigenous South African herbal teas enjoyed for their taste and aroma. Traditional medicinal uses of rooibos in South Africa include alleviation of infantile colic, allergies, asthma and dermatological problems, while a decoction of honeybush was used as a restorative and as an expectorant in chronic catarrh and pulmonary tuberculosis. Traditional medicinal uses of Athrixia phylicoides DC., or bush tea, another indigenous South African plant with very limited localised use as herbal tea, include treatment of boils, acne, infected wounds and infected throats. Currently rooibos and honeybush are produced for the herbal tea market, while bush tea has potential for commercialisation. A summary of the historical and modern uses, botany, distribution, industry and chemical composition of these herbal teas is presented. A comprehensive discussion of in vitro, ex vivo and in vivo biological properties, required to expand their applications as nutraceutical and cosmeceutical products, is included, with the main emphasis on rooibos. Future research needs include more comprehensive chemical characterisation of extracts, identification of marker compounds for extract standardisation and quality control, bioavailability and identification of bio-markers of dietary exposure, investigation of possible herb-drug interactions and plant improvement with regards to composition and bioactivity.

Postnatal development of pups from nursing rats treated with Gingko biloba

The Gingko biloba extract is contraindicated during pregnancy and lactation due to the lack of information about its effects on these reproductive phases. Previous studies have shown that G. biloba extract contains components with estrogenic and antiestrogenic activities, thus nursing dams treated with the extract of this plant could show reduction in milk production, resulting in malnutrition and poor development of pups. This work analyzes the postnatal development of pups, whose mothers were treated with G. biloba extract during the lactation period. Nursing Wistar rats received 3.5 mg/kg/day of G. biloba aqueous extract, corresponding to the highest human dose. Clinical signs of maternal toxicity were evaluated. The growth rate, viability, survival during treatment and lactation indices of the pups were calculated. The physical, motor and sensorial development of the pups was also evaluated. No maternal signs of toxicity were observed. As there were no biological differences between control and G. biloba treated pups, it is possible to assume that, in this experimental design, the administration of G. biloba aqueous extract to nursing rats during the lactation period seems to be devoid of toxic effect to mothers and to the physical, motor and sensory development of the pups.

An inventory of the ethnoveterinary practices for reproductive disorders in cattle and buffaloes, Sargodha district of Pakistan

AIM OF THE STUDY

This study was conducted to document the ethnoveterinary practices (EVPs) used for the treatment and/or management of reproductive disorders of cattle and buffaloes.

MATERIALS AND METHODS

The information was collected using rapid and participatory rural appraisal techniques through interviews and focused group discussions with 217 traditional veterinary healers (TVHs) over a period of 16 months.

RESULTS

The use of 66 plant species was documented for the treatment of reproductive disorders in the two dairy species. Most frequently reported (>or=20 times) plants represented Apiaceae, Poaceae, Pedaliaceae, Linaceae, Arecaceae, Brassicaceae, Malvaceae, Zingiberaceae, Rosaceae, Cannabaceae, Fabaceae, Moraceae, Rubiaceae and Mimosaceae families. All the documented plant species were indigenous to the study area. Genital prolapse, retention of fetal membranes, silent estrous/delayed puberty, anestrous, dystokia associated with incomplete cervical dilatation and retention of lochial discharge were the frequently reported reproductive disorders. Some of the plants were reported to be used in more than one condition. Materials other than plants used for the treatment of these disorders included camel milk, butter and butter fat, minerals, eggs, organic matters, chemical substances and meat preparations. These materials were used either alone or as adjunctive therapy.

CONCLUSION

Richness of EVPs in the study area and extensive variation in the doses, methods of preparation, indications, and claims regarding efficacy of plants for various disorders merit controlled studies for their validation.

Estrogen effects of Daldinia concentrica and Psathyrella efflorescens extracts in vitro

Daldinia concentrica and Psathyrella efflorescens are two fungi used in African traditional medicine. In the present study, their extracts were evaluated for their steroid activities in estrogen- or androgen-dependent cell lines using as endpoints steroid-dependent transcriptional activity and cell proliferation. Treatment of human breast cancer MCF-7 cells with 15 or 30 microg/ml of Daldinia concentrica or Psathyrellaefflorescens extracts in the absence of 17beta-estradiol (E2) significantly increased the transcriptional activity of an estrogen receptor (ER)-dependent reporter gene, in the same range as E2. Similar data were obtained in gonadotrope cell line alpha-T3-1. All the effects were prevented by the pure estrogen antagonist, ICI 182,780. In the absence of steroid addition, the two extracts induced cell proliferation of ER-dependent MCF-7 and Ishikawa Var-I cell lines by approximately 100% of the E2 response. Combination treatments with E2 showed no competitive or additive effects in the two latter cell lines. Interestingly, the extracts had no androgen-like response in androgen receptor (AR)-positive and ER-negative MDA-MB231 cells, suggesting that fungi effects are estrogen specific and extracts are not toxic at used concentrations. Results provided evidence that Daldinia concentrica or Psathyrellaefflorescens extracts induce estrogen-like effects in ER-positive cell lines, which could be responsible of the effects observed in vivo.

Antiestrogenic activities of Ginkgo biloba extracts

Most climacteric and postmenopausal women appear to have vasomotor symptoms as well as a high risk of osteoporosis and cardiovascular disease. Although exogenous estrogens can reduce these symptoms, women are reluctant to use hormone replacement therapy (HRT) due to its undesirable side effects, such as irregular bleeding and an increased risk of breast cancer. A previous study suggested that Ginkgo biloba extracts (GBE) have estrogenic activity and might be suitable as an alternative to HRT. However, there are no reports of the preventive effect of GBE on breast cancer, which is the side effect of classical HRT. In this study, it was confirmed that GBE exhibits estrogenic and antiestrogenic activity depending on the E2 and GBE concentration, via estrogen receptor (ER)-dependent and ER-independent pathways. In addition, GBE reduced the E2 levels by stimulating the E2 metabolism and inhibiting E2 synthesis, which indicates that GBE can induce antiestrogenic activity via the depletion of E2. Furthermore, GBE might have similar action to selective arylhydrocarbon receptor modulators (SAhRMs), which induce antiestrogenic activity through cross-talk between the arylhydrocarbon receptor (AhR) and ER. In conclusion, GBE has a biphasic effect on estrogen, and can be considered as a potential alternative to HRT with chemopreventive effects on breast cancer. However, further studies on animals and humans will be required.

Biphasic effects of kaempferol on the estrogenicity in human breast cancer cells

Dietary flavonoids have attracted a great deal of attention as agents for preventing estrogen-related diseases, such as postmenopausal symptoms, and for reducing the risk of estrogen-dependent cancer. Kaempferol is one of the most commonly found dietary phytoestrogen. The aim of this study was to investigate the estrogenic and/or antiestrogenic effect of kaempferol, which can confirm its potency as a preventive agent against estrogen-related diseases. Kaempferol has both estrogenic and antiestrogenic activity, which are biphasic response on estrogen receptor. The estrogenic activity of kaempferol induced via ER-mediated pathway depending on E2 concentration (< or = 10(-12) M). Kaempferol (10(-5) M) also caused antiproliferative effect on MCF-7 cell in the presence of E2 (10(-11) M) and restored to the addition of excess E2 (10(-7) M), which confirms that antiproliferation of kaempferol was induced via ER-dependent pathway. However, at 10(-4) M, concentration higher than the concentrations at which the estrogenic effects of kaempferol are detected (10(-5) M), kaempferol induced strong antiproliferative effect, but were unaffected by the addition of excess E2 (10(-7) M) indicating that kaempferol exerts antiproliferation via ER-independent pathway. In particular, kaempferol blocked the focus formation induced by E2, which confirms that kaempferol might inhibit the malignant transformation caused by estrogens. Therefore, we suggested that kaempferol might regulate a suitable level of estrogenic activity in the body and is expected to have potential beneficial effects in preventing estrogen imbalance diseases (breast cancer, osteoporosis, cardiovascular disease and etc.).

Estrogenic effect of procymidone through activation of MAPK in MCF-7 breast carcinoma cell line

Procymidone modifies sexual differentiation in vitro and induces estrogenic activity in primary cultured rainbow trout hepatocytes, as shown by an increase in the contents of vitellogenin and heat shock proteins. Since this dicarboximide fungicide is found in human tissues, it was considered of interest to investigate its ability to induce endocrine damage in the MCF-7 human cell line. The mechanism of this estrogenic action was also evaluated. Procymidone 100 microM stimulated cell growth from day 3 up to day 12 and raised the level of pS2 on day 3. Although procymidone does not bind the estrogen receptor (ER), the antiestrogen ICI 182780 inhibited its effect on cell growth and pS2 content, suggesting that the ER is involved indirectly in these effects. In exploring the mechanism of ER indirect activation we found that the antibody against c-Neu receptor (9G6) did not modify procymidone's effects on cell growth and pS2 expression. Thus, procymidone does not bind the c-Neu membrane receptor, excluding this indirect ER activation pathway. We also found that procymidone induced mitogen-activated protein kinase (MAPK) at 15 and 30 min, and that PD 98059, a MAPK (Erk1/2) inhibitor, prevented procymidone's effects on cell growth and pS2, indicating that MAPK activation is responsible for procymidone ER activation. The production of reactive oxygen species (ROS) with these times and elimination of the phenomenon by alpha-tocopherol (alpha-T), a ROS scavenger, is proof that oxygen free-radical production is at the basis of the MAPK activation by procymidone.

Estrogenic effects of marijuana smoke condensate and cannabinoid compounds

Chronic exposure to marijuana produces adverse effects on the endocrine and reproductive systems in humans; however, the experimental evidence for this presented thus far has not been without controversy. In this study, the estrogenic effect of marijuana smoke condensate (MSC) was evaluated using in vitro bioassays, viz., the cell proliferation assay, the reporter gene assay, and the ER competitive binding assay. The results of these assays were compared with those of three major cannabinoids, i.e., THC, CBD, and CBN. The estrogenic effect of MSC was further confirmed by the immature female rat uterotrophic assay. MSC stimulated the estrogenicity related to the ER-mediated pathway, while neither THC, CBD, nor CBN did. Moreover, treatment with 10 and 25 mg/kg MSC induced significant uterine response, and 10 mg/kg MSC resulted in an obvious change in the uterine epithelial cell appearance. MSC also enhanced the IGFBP-1 gene expression in a dose-dependent manner. To identify the constituents of MSC responsible for its estrogenicity, the MSC fractionated samples were examined using another cell proliferation assay, and the estrogenic active fraction was analyzed using GC-MS. In the organic acid fraction that showed the strongest estrogenic activity among the seven fractions of MSC, phenols were identified. Our results suggest that marijuana abuse is considered an endocrine-disrupting factor. Furthermore, these results suggest that the phenolic compounds contained in MSC play a role in its estrogenic effect.

Limited cognitive benefits in Stage +2 postmenopausal women after 6 weeks of treatment with Ginkgo biloba

Gingko biloba has cognitive benefits both in populations suffering from dementia and after acute treatment in healthy volunteers, with some evidence indicating that those with poorer cognitive performance show greater benefit. We have previously found that 1 week of treatment with ginkgo improved attention, memory and mental flexibility in post-menopausal women, but the evidence for any beneficial effects of longer treatment is less well-established. The present study aimed to determine whether cognitive benefits, similar to those previously found after 1 week of treatment, would persist after 6 weeks of treatment, and whether those with poorer cognitive performance would benefit more. In a placebo-controlled, double-blind study, postmenopausal women (aged 51-67 years) were randomly allocated to receive a standardized extract of ginkgo (LI 1370, Lichtwer Pharma, Marlow, UK) (one capsule/day of 120 mg, n = 45) or matching placebo (n = 42) for 6 weeks. According to an established reproductive staging system, subjects were divided into those in the early (Stage +1; mean age 55 years) and late (Stage +2: mean age 61 years) stages of menopause. At baseline and after 6 weeks of treatment, subjects completed tests of mental flexibility, planning, memory and sustained attention, and ratings of mood, sleepiness, bodily and menopausal symptoms. The only significant effects of ginkgo were in the test of mental flexibility, in which there were significant menopausal stage-ginkgo interactions. This was because subjects in Stage +2 required fewer trials to complete the task and made fewer errors after ginkgo treatment, whereas those in Stage +1 showed no benefits. Subjects in Stage +2 had poorer performance at baseline compared to those in Stage +1 both in this task and the test of planning ability. The beneficial effects of ginkgo were limited to the test of mental flexibility and to those with poorer performance.