Evaluation of estrogenic activity of plant extracts for the potential treatment of menopausal symptoms

Cimicifuga racemosa extract BNO 1055 inhibits proliferation of the human prostate cancer cell line LNCaP

Extracts from black cohosh (Cimicifuga racemosa, CR) exert an anti-proliferative action in human breast cancer cell cultures, which has been attributed to an anti-estrogenic effect. However, CR constituents do not bind to either of the known estrogen receptors. Thus, the anti-tumor effect of CR me be mediated by mechanisms not involving these receptors. Polycyclic aromatic hydrocarbons are toxic environmental pollutants, which indirectly act as anti-estrogens by activating the aryl hydrocarbon receptor (AhR). The AhR is widely expressed in mammalian tissues and tumors. A recent screening study demonstrated activation of the AhR by a variety of herbal extracts, among others, CR. Since activation of the AhR causes inhibition of growth of prostate cancer cells, we addressed the question, whether CR may not only inhibit growth of breast cancer--but also of prostate cancer cells. In the AhR ligand assay, the CR extract BNO 1055 reduced tracer binding to 71% of the control demonstrating interaction of constituents of this extract with the receptor. Under basal as well as under estradiol- and dihydrotestosterone stimulated conditions, the CR extract dose dependently inhibited proliferation of LNCaP cells. A significant reduction of cell growth was observed at a concentration as low as 50 ng/ml. Thus, it is demonstrated for the first time that CR compounds potently inhibit the growth of human prostate cancer cells in vitro. This anti-proliferative effect may be mediated via the AhR.

Red clover (Trifolium pratense) monograph: a clinical decision support tool

Red clover, a legume resembling soy is used by man as a phytoestrogen. Other uses include asthma, pertussis, cancer and gout. The authors systematically review this herb in terms of pharmacology, efficacy, safety, side effects, standardization, dosing, toxicology as well as other parameters.

Ultrafiltration tandem mass spectrometry of estrogens for characterization of structure and affinity for human estrogen receptors

Although hormone replacement therapy (HRT) is used by post-menopausal women for the relief of menopausal symptoms and the potential reduction of osteoporosis, HRT also increases their risk of Alzheimer's disease, stroke, breast cancer, and endometrial cancer. Since the majority of these effects are associated primarily with estrogen binding to only one of the estrogen receptors (ER), new assays are needed that can more efficiently evaluate ER-binding and identify ligands selective for ER-alpha and ER-beta. High performance liquid chromatography-tandem mass spectrometry (LC-MS-MS) was combined with ultrafiltration as a new method to investigate the relative binding of compounds to the ERs and to evaluate the structures of these estrogens. Mixtures of estradiol and six equine estrogens, including equilin, equilenin, 8,9-dehydroestrone, and their 17beta-hydroxyl derivatives, were assayed simultaneously to determine their relative binding to human ER-alpha and ER-beta. Estrogens containing a 17beta-OH group were found to have higher relative affinities for the estrogen receptors than their ketone analogs. In addition, 17beta-EN showed selectivity for binding to ER-beta over ER-alpha. The results were compared to the IC50 values obtained by using a conventional radiolabled estradiol competitive binding assay. Finally, the utility of negative ion electrospray tandem mass spectrometry for the unambiguous identification of these estrogen isomers was investigated. Several characteristic recyclization pathways during tandem mass spectrometry were identified, which might be useful for distinguishing related estrogens.

Pilot Evaluation of Black Cohosh for the Treatment of Hot Flashes in Women

BACKGROUND

Hot flashes cause significant morbidity in postmenopausal women, including women with breast cancer. We undertook a pilot study to estimate the effectiveness of black cohosh to reduce hot flashes.

METHODS

Women who reported significant hot flashes (> or = 14 per week) were enrolled. Black cohosh was given in the form of the commercial product Remifemin. The first week was a no-treatment baseline period, and therapy was given for the subsequent 4 weeks. Hot flash data were collected by daily questionnaires during baseline and treatment weeks. Adverse effects were recorded.

RESULTS

Twenty-one women completed the study. Their mean age was 56 years (range, 38-80). Thirteen patients had a history of breast cancer. Six patients were taking tamoxifen or raloxifene. Patients reported an average of 8.3 hot flashes per day during the baseline week. The reduction in mean daily hot flash frequency was 50% (95% CI, 34%-65%), while weekly hot flash scores were reduced 56% (95% CI, 40%-71%) at completion of the study. Overall, patients reported less trouble with sleeping, less fatigue, and less abnormal sweating. No patients stopped therapy because of adverse effects.

CONCLUSIONS

Black cohosh appeared to reduce hot flashes and had a low toxicity. The efficacy found in this trial seems to be more than would be expected by a placebo effect (20%-30% hot flash reduction in previous trials). These results suggest that further evaluation of this black cohosh preparation with a phase III randomized trial is indicated.

Nonestrogen Treatment Modalities for Vasomotor Symptoms Associated with Menopause

OBJECTIVE:

To systematically review the literature regarding the efficacy and safety of nonestrogen treatments for menopause-associated vasomotor symptoms not due to cancer or chemotherapy.

DATA SOURCES:

Pertinent literature and clinical studies were identified by searching MEDLINE (1966–February 2004) and EMBASE (1959–February 2004) using the key search terms vasomotor symptoms, hot flashes, and menopause. Bibliographies of relevant articles were reviewed for additional references.

STUDY SELECTION AND DATA EXTRACTION:

English-language articles reporting efficacy and safety of nonestrogen treatment modalities for perimenopausal and postmenopausal vasomotor symptoms were evaluated. All articles identified from the data sources were evaluated, and all information deemed relevant was included. Emphasis was placed on randomized, double-blind, placebo-controlled clinical trials, as these provide the best efficacy and safety data. Studies evaluating treatment of vasomotor symptoms from other causes, such as cancer or chemotherapy, were excluded.

DATA SYNTHESIS:

Prescription medications reviewed for efficacy and safety in postmenopausal vasomotor symptoms include clonidine hydrochloride, danazol, gabapentin, methyldopa, mirtazapine, progestins, propranolol hydrochloride, selective serotonin-reuptake inhibitors (SSRIs), and venlafaxine. Nonprescription therapies reviewed include black cohosh, dong quai, evening primrose oil, physical activity, phytoestrogens, and red clover.

CONCLUSIONS:

According to this systematic literature review, postmenopausal vasomotor treatments that have been shown to be safe and effective in short-term use include black cohosh, exercise, gabapentin, medroxyprogesterone acetate, SSRIs (ie, paroxetine hydrochloride), and soy protein. Initial, small reports are suggestive for efficacy in menopausal vasomotor symptoms with megestrol acetate and venlafaxine.

Perimenopausal and Postmenopausal Health

HEALTH ISSUE: The average age of natural menopause in Western societies is estimated to be 51 years; women in Canada can therefore expect to live, on average, a third of their lives in post-menopausal years. During these years women are at increased risk of chronic diseases such as osteoporosis and cardiovascular disease. KEY FINDINGS: Clinical and epidemiological data on women in perimenopause are limited. There are no adequate Canadian data on symptom severity and prevalence among perimenopausal and postmenopausal women. Scientific evidence is lacking to support or refute claims that commonly used botanical products can offer therapeutic relief of menopausal symptoms.Recent data from the Women's Health Initiative suggest that combined estrogen plus therapy increases the risk of stroke, coronary artery disease and breast cancer. Hormone therapy is no longer recommended for the prevention of chronic diseases for asymptomatic women. Stroke is an important issue for perimenopausal and postmenopausal women and sex differences may exist in the progestin treatment of stroke. Osteoporosis affects an estimated one in six women over the age of 50. DATA GAPS AND RECOMMENDATIONS: There is a need to conduct clinical and epidemiological research aimed at better understanding the menopausal transition and defining its clinical phases. Investigations aimed at alternative combinations and doses of hormone therapy and non-pharmaceutical alternatives in light of known risks and benefits are also necessary. Health care practitioners and women need to be educated on the risks and effective treatment related to cardiovascular disease so they can present for treatment more quickly and receive the most effective therapies.

Mycotoxins in root extracts of American and Asian ginseng bind estrogen receptors alpha and beta

The estrogenic activity of ginseng has been the subject of conflicting reports. Cell proliferation, induction of estrogen-responsive genes, and isolated cases of adverse reactions such as postmenopausal vaginal bleeding and gynecomastia have been reported after ginseng treatment. Other studies report antiproliferative effects with no induction of estrogen-responsive genes. We developed estrogen receptor (ER) alpha and ER alpha competitive binding assays using recombinant receptors and [(3)H]-17 alpha-estradiol to detect phytoestrogens in extracts of Asian ginseng root (Panax ginseng C. A. Meyer) and American ginseng root (Panax quinquefolius L.). Root extracts contained substances that bound both receptor isoforms. These substances had a two to three times greater affinity for ER alpha. Significantly higher binding was found in methanol extracts than in hot water extracts. Subsequent analysis of the extracts revealed significant ER binding attributable to zearalenone, the estrogenic mycotoxin produced by several Fusarium species. The ER showed no binding affinity for Rb1 and Rg1, the major ginsenosides found in P. quinquefolius and P. ginseng, respectively. Thus, ginseng extraction methods, plant species tested, and mycotoxin contaminants may help to explain the disparate literature reports. The prevalence and health significance of fungal contamination in herbal products used for medicinal purposes should be further investigated.

Estrogen-like activity of licorice root constituents: glabridin and glabrene, in vascular tissues in vitro and in vivo

Post-menopausal women have higher incidence of heart diseases compared to pre-menopausal women, suggesting a protective role for estrogen. The recently Women's Health Initiative (WHI) randomized controlled trial concluded that the overall heart risk exceeded benefits from use of combined estrogen and progestin as hormone replacement therapy for an average of five years among healthy postmenopausal US women. Therefore, there is an urgent need for new agents with tissue-selective activity with no deleterious effects. In the present study, we tested the effects on vascular tissues in vitro and in vivo of two natural compounds derived from licorice root: glabridin, the major isoflavan, and glabrene, an isoflavene, both demonstrated estrogen-like activities. Similar to estradiol-17beta (E2), glabridin (gla) stimulated DNA synthesis in human endothelial cells (ECV-304; E304) and had a bi-phasic effect on proliferation of human vascular smooth muscle cells (VSMC). Raloxifene inhibited gla as well as E2 activities. In animal studies, both intact females or after ovariectomy, gla similar to E2 stimulated the specific activity of creatine kinase (CK) in aorta (Ao) and in left ventricle of the heart (Lv). Glabrene (glb), on the other hand, had only the stimulatory effect on DNA synthesis in vascular cells, with no inhibition by raloxifene, suggesting a different mechanism of action. To further elucidate the mechanism of action of glb, cells were pre-incubated with glb and then exposed to either E2 or to gla; the DNA stimulation at low doses was unchanged but there was abolishment of the inhibition of VSMC cell proliferation at high doses as well as inhibition of CK stimulation by both E2 and by gla. We conclude that glb behaved differently than E2 or gla, but similarly to raloxifene, being a partial agonist/antagonist of E2. Glabridin, on the other hand, demonstrated only estrogenic activity. Therefore, we suggest the use of glb with or without E2 as a new agent for modulation of vascular injury and atherogenesis for the prevention of cardiovascular diseases in post-menopausal women.

Ginsenoside-Rb1 from Panax ginseng C.A. Meyer activates estrogen receptor-alpha and -beta, independent of ligand binding

We studied the estrogenic activity of a component of Panax ginseng, ginsenoside-Rb1. The activity of ginsenoside-Rb1 was characterized in a transient transfection system, using estrogen receptor isoforms and estrogen-responsive luciferase plasmids, in COS monkey kidney cells. Ginsenoside-Rb1 activated both alpha and beta estrogen receptors in a dose-dependent manner with maximal activity observed at 100 microm, the highest concentration examined. Activation was inhibited by the estrogen receptor antagonist ICI 182,780, indicating that the effects were mediated through the estrogen receptor. Treatment with 17beta-estradiol or ginsenoside-Rb1 increased expression of the progesterone receptor, pS2, and estrogen receptor in MCF-7 cells and of AP-1-driven luciferase genes in COS cells. Although these data suggest that it is functionally very similar to 17beta-estradiol, ginsenoside-Rb1 failed to displace specific binding of [(3)H]17beta-estradiol from estrogen receptors in MCF-7 whole-cell ligand binding assays. Our results indicate that the estrogen-like activity of ginsenoside-Rb1 is independent of direct estrogen receptor association.

Cimicifuga racemosa extract inhibits proliferation of estrogen receptor-positive and negative human breast carcinoma cell lines by induction of apoptosis

Hormone replacement therapy is contraindicated in women with breast cancer. Extracts from the rhizomes of Cimicifuga racemosa, have gained acceptance as a natural alternative for the treatment of menopausal symptoms. In the present study we investigated the antiproliferative activity of C. racemosa extracts (isopropanolic and ethanolic) on the estrogen receptor positive MCF-7 and estrogen receptor negative MDA-MB231 breast cancer cells by WST-1 assay. Down regulation of the proliferative activity and cell killing by isopropanolic and ethanolic extracts occurred in a clear dose-dependent response with a 50% growth inhibitory concentration of 54.1 +/- 11.4 and 80.6 +/- 17.7 micro g/ml in MCF-7 cells and of 29.5 +/- 3.0 and 58.6 +/- 12.6 microg/ml in MDA-MB231 cells, respectively. Further, the mode of cell death was identified as apoptosis by microscopic inspection and confirmed by light scatter characteristics and by detection of Annexin V adherence to phosphatidylserine by flow cytometry. In addition, the involvement of activated caspases was supported by the cleavage of cytokeratin 18 detected with M30 antibody. Increases in the level of M30-antigen of about 4-fold and 2-fold over untreated controls were observed in C. racemosa -treated MCF-7 and MDA-MB231 cells. These results indicate that C. racemosa extract exerts no proliferative activity, but kills the estrogen receptor positive MCF-7 as well as estrogen receptor negative MDA-MB231 cells by activation of caspases and induction of apoptosis.

Treatment of menopause-associated vasomotor symptoms: position statement of The North American Menopause Society

OBJECTIVE

To create an evidence-based position statement regarding the treatment of vasomotor symptoms associated with menopause.

DESIGN

The North American Menopause Society (NAMS) enlisted clinicians and researchers acknowledged to be experts in the field of menopause-associated vasomotor symptoms to review the evidence obtained from the medical literature and develop a document for final approval by the NAMS Board of Trustees.

RESULTS

For mild hot flashes, lifestyle-related strategies such as keeping the core body temperature cool, participating in regular exercise, and using paced respiration have shown some efficacy without adverse effects. Among nonprescription remedies, clinical trial results are insufficient to either support or refute efficacy for soy foods and isoflavone supplements (from either soy or red clover), black cohosh, or vitamin E; however, no serious side effects have been associated with short-term use of these therapies. Single clinical trials have found no benefit for dong quai, evening primrose oil, ginseng, a Chinese herbal mixture, acupuncture, or magnet therapy. Few data support the efficacy of topical progesterone cream; safety concerns should be the same as for other progestogen preparations. No clinical trials have been conducted on the use of licorice for hot flashes. Among nonhormonal prescription options, the antidepressants venlafaxine, paroxetine, and fluoxetine and the anticonvulsant gabapentin have demonstrated some efficacy for treating hot flashes and were well tolerated. Two antihypertensive agents, clonidine and methyldopa, have shown modest efficacy but with a relatively high rate of adverse effects. For moderate to severe hot flashes, systemic estrogen therapy, either alone (ET) or combined with progestogen (EPT) or in the form of estrogen-progestin oral contraceptives, has been shown to significantly reduce hot flash frequency and severity. Clinical trials have associated ET/EPT with adverse effects, including breast cancer, stroke, and thromboembolism. Several progestogens (both oral and intramuscular formulations) have shown efficacy in treating hot flashes, including women with a history of breast cancer, although no definitive data are available on long-term safety in these women.

CONCLUSIONS

In women who need relief for mild vasomotor symptoms, NAMS recommends first considering lifestyle changes, either alone or combined with a nonprescription remedy, such as dietary isoflavones, black cohosh, or vitamin E. Prescription systemic estrogen-containing products remain the therapeutic standard for moderate to severe menopause-related hot flashes. Recommended options for women with concerns or contraindications relating to estrogen-containing treatments include prescription progestogens, venlafaxine, paroxetine, fluoxetine, or gabapentin. Clinicians are advised to enlist women's participation in decision making when weighing the benefits, harms, and scientific uncertainties of therapeutic options. Regardless of the management strategy adopted, treatment should be periodically reassessed as menopause-related vasomotor symptoms will abate over time without any intervention in most women.

Trifolium pratense for breast disease: a case series

A series of cases in which Trifolium pratense was used in breast disease with hyperoestrogenic symptoms is reported. Several patients with cystic mastosis and breast cancer appeared to do well. The 'picture' of Trifolium is discussed.

Estrogen Bioassay of Ginseng Extract and Arginmax®, a Nutritional Supplement for the Enhancement of Female Sexual Function

PURPOSE

To determine whether ArginMax (The Daily Wellness Co., Sunnyvale, CA) or the Panax ginseng extract it contains has any estrogenic activity. ArginMax for Women, a nutritional supplement for optimization of sexual health, contains L-arginine, ginseng, ginkgo, damiana, multivitamins, and minerals.

METHODS

A human endometrial adenocarcinoma cell line, Ishikawa, which contains an alkaline phosphatase (AP) enzyme sensitive to estrogen stimulation, was used in a bioassay to determine whether Panax ginseng or ArginMax contained estrogenic components.

RESULTS

Neither ArginMax nor Panax ginseng stimulated AP at any of the concentrations tested.

CONCLUSIONS

No estrogenic activity was evident in the sample of Panax ginseng extract tested or in a sample of ArginMax containing this extract in combination with other ingredients.

Influence of marketed herbal menopause preparations on MCF-7 cell proliferation

OBJECTIVE

Given the increasing use of alternative menopause treatments, we evaluated the effect of several herbal preparations used for menopause relief on the proliferation of estrogen-sensitive breast cancer cells (MCF-7) as a means of assessing appropriateness for use in women at risk for estrogen-sensitive breast cancer.

DESIGN

An MCF-7 cell culture model, as described previously, was used to evaluate the estrogen-agonist and -antagonist activity of commercially available herbal menopause preparations containing red clover, soy, black cohosh, or a combination of herbs. Each test substance was evaluated for cytotoxic effects before conducting the proliferation assays.

RESULTS

Commercially available products containing soy, red clover, and herbal combinations induced an increase in the MCF-7 proliferation rates, indicating an estrogen-agonistic activity in the absence of estradiol. In contrast, an isopropanolic black cohosh extract (Remifemin Menopause) did not stimulate MCF-7 growth and exerted inhibitory effects on cellular proliferation. None of the tested products enhanced estradiol-induced cell proliferation. The black cohosh preparation and one of the herbal combinations exhibited strong estrogen-antagonistic effects.

CONCLUSIONS

The lack of proliferative effects of isopropanolic black cohosh extract on estrogen-sensitive breast cancer cells in vitro suggests a favorable safety profile for use in women with a history of breast cancer. Alternatively, preparations containing red clover, soy, and combinations of various herbal ingredients may induce cell proliferation, suggesting that such herbal preparations should be used with caution in the treatment of menopause symptoms in women at risk for, or with a history of, estrogen-sensitive breast cancer.

Immune system effects of echinacea, ginseng, and astragalus: a review

Traditional herbal medicine provides several remedies for strengthening the body's resistance to illness through effects on immune system components. This review article examines 3 popular herbal immune stimulants that are often of interest to cancer patients. Echinacea, a native of North America, is widely used to prevent, or provide early treatment for, colds. Preclinical studies lend biological plausibility to the idea that echinacea works through immune mechanisms. Numerous clinical trials have been carried out on echinacea preparations: it appears that the extracts shorten the duration and severity of colds and other upper respiratory infections (URIs) when given as soon as symptoms become evident. However, trials of long-term use of echinacea as a preventive have not shown positive results. Ginseng has been studied in some depth as an antifatigue agent, but studies of immune mechanisms have not proceeded so far. Preclinical evidence shows some immune-stimulating activity. There have been several clinical trials in a variety of different diseases. Astragalus is the least-studied agent. There are some preclinical trials that show intriguing immune activity. The herbs discussed appear to have satisfactory safety profiles. Cancer patients may wish to use these botanicals to inhibit tumor growth or to boost resistance to infections. However, passive immunotherapy with herbs, with no mechanism to expose tumor antigens, is unlikely to be effective in inhibiting tumor growth. Although the margin of safety for these herbs is large, more research is needed to demonstrate the clear value of using herbs to improve resistance to infections.

Phyto-oestrogens and breast cancer chemoprevention

Phytoestrogens are polyphenol compounds of plant origin that exhibit a structural similarity to the mammalian steroid hormone 17β-oestradiol. In Asian nations the staple consumption of phyto-oestrogen-rich foodstuffs correlates with a reduced incidence of breast cancer. Human dietary intervention trials have noted a direct relationship between phyto-oestrogen ingestion and a favourable hormonal profile associated with decreased breast cancer risk. However, these studies failed to ascertain the precise effect of dietary phyto-oestrogens on the proliferation of mammary tissue. Epidemiological and rodent studies crucially suggest that breast cancer chemoprevention by dietary phyto-oestrogen compounds is dependent on ingestion before puberty, when the mammary gland is relatively immature. Phyto-oestrogen supplements are commercially marketed for use by postmenopausal women as natural and safe alternatives to hormone replacement therapy. Of current concern is the effect of phyto-oestrogen compounds on the growth of pre-existing breast tumours. Data are contradictory, with cell culture studies reporting both the oestrogenic stimulation of oestrogen receptor-positive breast cancer cell lines and the antagonism of tamoxifen activity at physiological phyto-oestrogen concentrations. Conversely, phyto-oestrogen ingestion by rodents is associated with the development of less aggressive breast tumours with reduced metastatic potential. Despite the present ambiguity, current data do suggest a potential benefit from use of phyto-oestrogens in breast cancer chemoprevention and therapy. These aspects are discussed.

Herbal product use and menopause symptom relief in primary care patients: a MetroNet study

OBJECTIVES

The four study objectives were to determine (1) the prevalence of use of four herbal product types promoted to reduce menopause symptoms (phytoestrogens, St. John's wort, Ginkgo biloba, and ginseng) among primary care patients approaching or in menopause, (2) the extent to which women who use these types of herbal products report menopause-related symptoms compared with herbal product nonusers, (3) the frequency of reported symptom reduction after use, and (4) if use was disclosed to their physicians.

METHODS

A cross-section of ethnically diverse women 40-55 years of age (35.5% African American, 60.2% Caucasian) who were recruited from eight primary care centers in Michigan to complete a self-report survey. The questionnaire included demographic items, health history, recent use of four herbal product types purported to relieve menopause symptoms and perception of symptom improvement, and interest in additional herbal product information.

RESULTS

Of 397 women, 24.9% reported taking, in the previous 6 months, at least one of the four study herbs. Herbal product use did not vary by patient demographics or health characteristics. Herbal product users reported more menopause symptoms than nonusers, and 68% of the users said that the herbs improved their symptoms; 56.4% said that their physician was aware of their herbal product use.

CONCLUSIONS

Primary care patients experiencing common menopausal symptoms are likely to use herbal products that are purported to provide menopause symptom relief, and many believe that these products improve their menopausal symptoms. Healthcare providers should be aware of patient's positive attitude, use patterns, and lack of disclosure of use of herbal medicines. Inquiry of herbal product use is another way for physicians to learn about patient self-medication of bothersome symptoms.

Isolation of linoleic acid as an estrogenic compound from the fruits of Vitex agnus-castus L. (chaste-berry)

A methanol extract of chaste-tree berry (Vitex agnus-castus L.) was tested for its ability to displace radiolabeled estradiol from the binding site of estrogen receptors alpha (ERalpha) and beta (ERbeta). The extract at 46 +/- 3 microg/ml displaced 50% of estradiol from ERalpha and 64 +/- 4 microg/ml from ERbeta. Treatment of the ER+ hormone-dependent T47D:A18 breast cancer cell line with the extract induced up-regulation of ERbeta mRNA. Progesterone receptor (PR) mRNA was upregulated in the Ishikawa endometrial cancer cell line. However, chaste-tree berry extract did not induce estrogen-dependent alkaline phosphatase (AP) activity in Ishikawa cells. Bioassay-guided isolation, utilizing ER binding as a monitor, resulted in the isolation of linoleic acid as one possible estrogenic component of the extract. The use of pulsed ultrafiltration liquid chromatography-mass spectrometry, which is an affinity-based screening technique, also identified linoleic acid as an ER ligand based on its selective affinity, molecular weight, and retention time. Linoleic acid also stimulated mRNA ERbeta expression in T47D:A18 cells, PR expression in Ishikawa cells, but not AP activity in Ishikawa cells. These data suggest that linoleic acid from the fruits of Vitex agnus-castus can bind to estrogen receptors and induce certain estrogen inducible genes.

Phytoestrogens: a review of the present state of research

Phytoestrogens are a diverse group of plant-derived compounds that structurally or functionally mimic mammalian estrogens and show potential benefits for human health. The number of articles published on phytoestrogens has risen dramatically in the past couple decades. Further research continues to demonstrate the biological complexity of phytoestrogens, which belong to several different chemical classes and act through diverse mechanisms. This paper discusses the classification of phytoestrogens, methods of identification, their proposed mechanisms of action and botanical sources for phytoestrogens. The effects of phytoestrogens on breast and prostate cancers, cardiovascular disease, menopausal symptoms and osteoporosis will also be examined including research on benefits and risks.

Nutritional Approaches to Late Toxicities of Adjuvant Chemotherapy in Breast Cancer Survivors

Adjuvant chemotherapy of breast cancer reduces recurrence rates and prolongs survival at the cost of both acute and chronic toxicities. Breast cancer survivors who have received adjuvant chemotherapy may suffer from late effects of chemotherapy including congestive heart failure, neuropathy, premature menopause, and osteoporosis. Nutritional approaches to these problems are distinct in their orientation and success. Study of free radical scavengers for anthracycline-induced cardiomyopathy was born from known pathogenetic mechanisms of cardiotoxicity but has been universally disappointing thus far in clinical trials. Application of agents used for diabetic neuropathy suggests that evening primrose oil, alpha-lipoic acid, and capsaicin may all play a role in the empiric options available to patients with chemotherapy-induced neuropathy. Plant-derived preparations including black cohosh (Actaea racemosa), dong quai (Angelica sinensis), evening primrose (Oenothera biennis), and red clover (Trifolium pretense) are used by patients experiencing hot flashes due to premature menopause despite a paucity of clinical trial data demonstrating either safety or efficacy. Calcium and vitamin D are widely accepted as an effective means to retard bone loss leading to osteoporosis. Nutritional approaches to late effects of breast cancer chemotherapy offer the prospect of preventing or ameliorating these sequelae of treatment. However, except for vitamin D and calcium for prevention of bone loss, current clinical evidence supporting use of nutritional agents remains sparse.

High isoflavone content and estrogenic activity of 25 year-old Glycine max tissue cultures

Soy isoflavones are phytoestrogens which have been associated with several health benefits. In the present study, we report the production of isoflavones in a collection of 40 strains of soya cell cultures established in 1975. A large variability in the isoflavone composition was observed and high-producing strains, with an isoflavone content of up to 46.3 mg g(-1) dry wt., were found. In comparison with soybeans, many callus strains had a higher isoflavone concentration (10-40 times) and a different ratio of genistin to daidzin forms. The highest producing strain was transferred to liquid medium in an Erlenmeyer flask and in a 10 l stirred-tank bioreactor where high isoflavone content (7% dry wt.), concentration (880 mg l(-1)) and a maximum productivity estimated to 60 mg l(-1) d(-1) were obtained. We further studied the estrogenic activity of pure compounds compared to plant cell culture extracts in the estrogen-responsive human endometrial Ishikawa cell line. Estrogen was confirmed to be 1000-10,000 times more active than isoflavones. The estrogenic activity of the extracts correlated to their isoflavone content. The activity of the malonyl isoflavones, assessed here for the first time, was lower than the aglycones. Taken together, these results suggest that soya cell cultures can be used as an alternative source to soybeans to provide high concentrations of bioactive isoflavones.

Alternatives to estrogen

For many years, women have sought alternative therapies for menopausal symptoms and for general health overall. The highly publicized findings from the Women's Health Initiative have led to an increased pressure on the medical community to find safe and alternative medications for female health. This article reviews the challenges and problems with the use of alternative medicines, and the clinical trials that prove their efficacy, and discusses the safety issues that may occur with these types of products.

Pharmacological effects of Cimicifuga racemosa

Cimicifuga racemosa is widely employed to relieve menopause symptoms for its hormonal-like action. However, recent experimental studies have not found an estrogenic action by this plant. The purpose of this systematic review is to analyse all experimental studies (in vivo and in vitro) performed on C. racemosa to elucidate its mechanism of action. Animal and in vitro experiments on C. racemosa were identified through a computerised literature searches performed on Medline (PubMed), Embase, Amed, CISCOM and Cochrane Library databases. In addition, bibliographies of the articles thus located were scanned for further relevant publications and manufactures of commercial C. racemosa preparations were asked to contribute published and unpublished material. No language restrictions were imposed. A total of 15 animal and 15 in vitro studies on C. racemosa have been found. Their results suggest that C. racemosa possesses a central activity instead of a hormonal effect. Further biological and chemical investigations are required to define its mechanism of action and to identify the compounds responsible of its actions.

Critical evaluation of the safety of Cimicifuga racemosa in menopause symptom relief

OBJECTIVE

This comprehensive review examines the safety of Cimicifuga racemosa for the treatment of menopause symptoms, particularly in populations in which conventional menopause treatment regimens, including estrogen replacement, are contraindicated.

DESIGN

An extensive database of information on Cimicifuga, which included all published literature pertaining to preclinical and clinical safety of various forms of Cimicifuga, the FDA and World Health Organization adverse-event reporting systems, monographs, compendia, internal unpublished data from a major manufacturer, foreign literature, and historical anecdotal reports, was reviewed, and findings pertaining to the safety of Cimicifuga use for menopause treatment were reported.

RESULTS

Uncontrolled reports, postmarketing surveillance, and human clinical trials of more than 2,800 patients demonstrate a low incidence of adverse events (5.4%). Of the reported adverse events, 97% were minor and did not result in discontinuation of therapy, and the only severe events were not attributed to Cimicifuga treatment.

CONCLUSIONS

Although the effects of Cimicifuga may be dependent on the specific extract preparation, this review clearly supports the safety of specific Cimicifuga extracts, particularly isopropanolic preparations, for use in women experiencing menopausal symptoms and as a safe alternative for women in whom estrogen therapy is contraindicated.

In vitro effects of the Cimicifuga racemosa extract BNO 1055

OBJECTIVES

Extracts of Black cohosh (Cimicifuga racemosa or CR) have been used for the treatment of climacteric complaints since decades. Efficacy, particularly concerning neurovegetative and psychic symptoms, has been proven in clinical trials. As active principle yet unknown substances with selective estrogen receptor modulator (SERM) activity are assumed. Recently, evidence arose that CR may also contain dopaminergic compounds, which may contribute to the therapeutic activity of the extract.

METHODS

Two subtypes of the estrogen receptor (ERalpha and ERbeta) are known. To examine, whether active substances of CR extract BNO 1055 (which is contained in Klimadynon and Menofem) bind to either of the two estrogen receptors, subtype-specific estrogen receptor ligand-binding assays with recombinant ERalpha or ERbeta were conducted. A ligand-binding assay with recombinant dopamine D(2)-receptor protein was employed to assess possible dopaminergic activity in the CR extract BNO 1055.

RESULTS

While a displacement of radiolabeled estradiol from binding sites of a cytosol preparation from procine and human endometrium by CR extract BNO 1055 was shown no such displacement was achieved when either ERalpha or ERbeta protein was used as ligands for tracer. Dopaminergic activity in the CR extract BNO 1055 could be demonstrated with the D(2)-receptor assay. A countercurrent chromatography resulted in a separation of estrogenic and dopaminergic activity in two distinct fractions.

CONCLUSIONS

It is suggested that not yet identified substances in the CR extract BNO 1055 bind to a yet unknown estrogen-binding site in the endometrium. Also, yet unknown dopaminergic compounds may contribute to the pharmacological profile of CR extract BNO 1055.

Phytoestrogens--mechanism of action and effect on bone markers and bone mineral density

Dietary supplements, especially those containing phytoestrogens, frequently are used to either promote health or prevent disease. An estimated 20 billion dollars was spent on dietary supplements in the year 2000. Approximately 40% to 55% of Americans use supplements on a regular basis and 24% of these supplements contain herbs. Phytoestrogens are defined as any compound that is structurally or functionally related to ovarian or placental estrogens and their active metabolites. These compounds are widely used for various disorders related to women's health.

Panax ginseng: a role in cancer therapy?

Panax ginseng is a plant that has been used in traditional medicine in China for thousands of years. It is used as a general tonic or adaptogen with chronically ill patients and is frequently featured in traditional medicine prescriptions from China, Japan, and Korea used by cancer patients. The putative active compounds are the ginsenosides, of which there are more than two dozen. These compounds are found in both Panax ginseng and in other Panax species that are used in herbal medicine. Analysis of ginsenosides is being used in developing quality control assessments for ginseng, which has frequently been adulterated due to its high cost; many currently available standardized extracts do appear to contain the amounts of ginsenosides listed on package labeling. The toxicity of ginseng appears to be low: some of the reports of toxic episodes of ginseng may actually pertain to other components of multicomponent preparations. Very low incidence of toxicity has been observed in ginseng clinical trials using well-characterized preparations. Numerous pharmacological activities of ginseng and the ginsenosides have been explored: the authors review here the activities relating to cancer. Immune system modulation, antistress activities, and antihyperglycemic activities are among the most notable features of ginseng noted in laboratory and clinical analyses. Much testing has been done in humans to explore ginseng's purported antifatigue properties, but this area remains controversial. A number of investigations point to antitumor properties and other pharmacological activities related to cancer, but no trials have yet confirmed a clinically significant anticancer activity. Cancer patients may empirically find ginseng to be useful when they are fatigued, although clinical trials should be conducted to confirm its benefits.

A ginsenoside-Rh1, a component of ginseng saponin, activates estrogen receptor in human breast carcinoma MCF-7 cells

We have examined the possibility that a component of Panax ginseng, ginsenoside-Rh1, acts by binding to steroid hormone receptors such as receptors for estrogen, glucocorticoid, androgen, and retinoic acid. Ginsenoside-Rh1 activated the transcription of the estrogen-responsive luciferase reporter gene in MCF-7 breast cancer cells at a concentration of 50 microM. Activation was inhibited by the specific estrogen receptor antagonist ICI 182,780, indicating that the estrogenic effect of ginsenoside-Rh1 is estrogen receptor dependent. Ginsenoside-Rh1 induction of luciferase activity was dose-dependent in CV-1 cells transiently transfected with estrogen receptor and reporter plasmids. Next, we evaluated the ability of ginsenoside-Rh1 to induce the estrogen-responsive genes in MCF-7 cells. Ginsenoside-Rh1 increased c-fos and pS2 at the mRNA levels at 24h after treatment, although the effects were not as prominent as 17beta-estradiol. Western blot analysis showed that progesterone receptor protein was induced at 24h of treatment of ginsenoside-Rh1. However, ginsenoside-Rh1 failed to activate the glucocorticoid receptor, the androgen receptor, or the retinoic acid receptor in CV-1 cells transiently transfected with the corresponding steroid hormone receptors and hormone responsive reporter plasmids. These data support our hypothesis that ginsenoside-Rh1 acts as a weak phytoestrogen, presumably by binding and activating the estrogen receptor.

Stimulation of alkaline phosphatase activity in Ishikawa cells induced by various phytoestrogens and synthetic estrogens

Xenoestrogens, phytoestrogens and synthetic estrogens, are able to bind to estrogen receptors, and to mimic estrogenic activities in a cell and tissue specific manner. For the characterization of environmental estrogens mainly mammary derived and yeast based models have been used. The aim of this study was therefore to assess selected natural and synthetic compounds in an endometrial derived model. We measured the relative estrogenic potency of phytoestrogens (genistein, daidzein, coumestrol, some naringenins), synthetic estrogens (bisphenol A, octylphenol, nonylphenol, o,p'-DDT), mycoestrogen (zearalanone) as well as extracts of Cimicifuga racemosa on alkaline phosphatase (AlkP) activity in the endometrial derived adenocarcinoma cell line Ishikawa. We used a modified multiwell plate in vitro bioassay based on the estrogen-specific and dose-dependent enhancement of AlkP activity in this cell line. Estradiol, which induced AlkP at levels as low as 10(-8)M, was used as positive control. Most of the compounds studied showed a clear dose-dependent estrogenic effect. Compared to the vehicle control (ethanol) all phyto- and mycoestrogens, stimulated the AlkP activity 2-4-fold at a concentration of 10(-6)M. The synthetic chemicals bisphenol A and nonylphenol showed an effect at 10(-6)M, octylphenol at 10(-5)M. Effects of o,p'-DTT could not be measured. ICI 182,780, a pure estrogen receptor antagonist, significantly inhibited these effects. The latter result demonstrated the estrogen receptor dependency of this process. In summary, most of the phytoestrogens and industrial chemicals tested, behaved as estrogen receptor agonists in terms of the stimulation of AlkP activity.

Phytoestrogens for hormone replacement therapy?

Due to some severe side effects "classical" hormone replacement therapy (HRT) is currently being challenged by a therapy with phytoestrogens. Particularly soy and red clover derived isoflavones are advertised as selective estrogen receptor modulators (SERMs) with only desired and no undesired estrogenic effects. Evidence that this is the case however is scarce. Most studies investigating climacteric complaints did not find beneficial effects. A proposed beneficial effect on mammary cancer is unproven. The majority of studies however indicate an antiosteoporotic effect of isoflavones, while putative beneficial effects in the cardiovascular system are questionable due to the fact that estradiol which--like isoflavones--increase HDL and decrease LDL concentrations appear not to prevent arteriosclerosis in the human. In the urogenital tract, including the vagina, soy and red clover derived isoflavones are without effects. Cimicifuga racemosa extracts are traditionally used for the treatment of climacteric complaints. Evidence is now available that the yet unknown compounds in Cimicifuga racemosa extracts prevent climacteric complaints and may also have antiosteoporotic effects.

Pathophysiology and treatment of hot flashes

Hot flashes affect about three fourths of postmenopausal women and are one of the most common health problems in this demographic group. Dysfunction of central thermoregulatory centers caused by changes in estrogen levels at the time of menopause has long been postulated to be the cause of hot flashes. Treatment should begin with a careful patient history, with specific attention to the frequency and severity of hot flashes and their effect on the individual's function. For mild symptoms that do not interfere with sleep or daily function, behavioral changes in conjunction with vitamin E (800 IU/d) use is a reasonable initial approach. For more severe symptoms, the next step is to determine whether there is a contraindication or a personal reservation to estrogen replacement therapy. For women who are able and willing to use estrogen, it will successfully relieve symptoms by about 80% to 90%. In patients with a history of breast or uterine cancer, treatment with the progestational agent megesterol acetate appears to be a safe alternative that also decreases hot flashes by approximately 80%. For women unwilling or unable to use hormone therapy, one of the newer antidepressant agents can be prescribed. Venlafaxine decreases hot flashes by about 60%. Gabapentin is another drug that appears promising as therapy for women unable or unwilling to use estrogen, and the results of ongoing trials to determine its efficacy are eagerly awaited. The use of clonidine, methyldopa, and belladonna should be discouraged because of their modest efficacy and adverse effects.

Black cohosh: an alternative therapy for menopause?

Due to the long-term health risks now associated with hormone replacement therapy, many menopausal women are actively seeking alternative treatments. One such alternative is black cohosh (Actaea racemosa, syn. Cimicifuga racemosa), which has been used in the United States for the treatment of gynecologic complaints for more than 100 years. Review of the published clinical data suggests that black cohosh may be useful for the treatment of menopausal symptoms, such as hot flashes, profuse sweating, insomnia, and anxiety. Results from the most recently published trial, however, indicate that black cohosh is not effective for the treatment of menopausal symptoms in breast cancer survivors being treated with tamoxifen. Because the overall quality of the published clinical trials is low, two new randomized, double-blind, placebo-controlled clinical trials are currently underway in the United States. To date, only one standardized black cohosh extract has been tested clinically; the current recommended dose is 40-80 mg per day. At least 4-12 weeks of treatment may be required before any therapeutic benefits may be apparent. Adverse reactions such as nausea, vomiting, headaches, dizziness, mastalgia, and weight gain have been observed in clinical trials. No drug interactions are reported in the medical literature. The estrogenic effects of black cohosh are controversial, and the more recent data indicate that black cohosh extracts may have an anti-estrogenic activity. Owing to potential effects on sex hormones, however, black cohosh should not be administered to children or during pregnancy and lactation.

Effect of Angelica sinensis on the proliferation of human bone cells

BACKGROUND

Angelica sinensis, an herbal medicine known for its effect to purify blood quality and improve circulation, frequently appears as the main ingredient in prescriptions for bone injuries. Currently, how pharmacologically it contributes to the reformation of bone is unclear.

METHODS

The effect of the aqueous extract of Angelica sinensis on bone cells was investigated in vitro for the first time. The human osteoprecursor cells (OPC-1) were incubated in the medium with different concentrations of the aqueous extract of Angelica sinensis and the cell proliferation was studied.

RESULTS

When the concentration of Angelica sinensis aqueous extract was <125 microg/ml, the proliferation of OPC-1 was enhanced. However, the proliferation of OPC-1 was inhibited by Angelica sinensis extract with the concentrations >250 microg/ml. Under most treatments, the cells presented very pale expression for cyclooxygenase-2 (Cox 2) protein; slightly intensified band showed at the highest Angelica sinensis concentration, 1.0 mg/ml during the course of culture.

CONCLUSION

The aqueous extract of Angelica sinensis was found to directly stimulate the proliferation, alkaline phosphatase (ALP) activity, protein secretion and particularly type I collagen synthesis of OPC-1 at dose-dependent manner.

Yeast reporter system for rapid determination of estrogenic activity

An in vitro test system for the determination of estrogens, xeno- and phytoestrogens, based on the activation of human estrogen receptor-alpha, has been examined for ability in monitoring environmental estrogens. The system consists of an expression plasmid for the human estrogen receptor-alpha and a reporter plasmid containing the lacZ gene under the control of the vitellogenin hormone response element. These plasmids have been transformed into S. cerevisae. Cultivation of yeast in the presence of estrogenic substances leads to activation of the estrogen receptor and induces the expression of the reporter lacZ. beta-Galactosidase activity of the translated gene lacZ is a measure of the estrogenic activity of a compound. First, the selectivity of the system was compared to data available in the literature. Then the sensitivity of the system was checked. The detection limit is 0.1 ng 17-beta estradiol or an equivalent activity per liter, if a sample can be concentrated 1000-fold. The system has been further characterized by selected compounds with known and unknown estrogenic activity.

Isoflavones from red clover (Promensil) significantly reduce menopausal hot flush symptoms compared with placebo

OBJECTIVES

To investigate the effectiveness and safety of a red clover isoflavone dietary supplement (Promensil, Novogen Ltd., Australia) versus placebo on the change in hot flush frequency in postmenopausal women.

METHODS

In this randomized, double blind, placebo-controlled trial 30 women with more than 12 months amenorrhoea and experiencing more than five flushes per day were enrolled. All received single blind placebo tablets for 4 weeks and were subsequently randomized to either placebo or 80 mg isoflavones for a further 12 weeks. Efficacy was measured by the decrease in number of hot flushes per day and changes in Greene Climacteric Scale Score.

RESULTS

During the first 4 weeks of placebo the frequency of hot flushes decreased by 16%. During the subsequent double blind phase, a further, statistically significant decrease of 44% was seen in isoflavones group (P<0.01), whereas no further reduction occurred within the placebo group. The Greene score decreased in the active group by 13% and remained unchanged in the placebo group.

CONCLUSION

In this study, treatment with 80 mg isoflavones (Promensil) per day resulted in a significant reduction in hot flushes from baseline. At the end of the study there was a significant decrease in hot flushes of 44% between the active and placebo group, demonstrating the effectiveness of Promensil in the management of hot flushes.

Analysis of thirteen populations of black cohosh for formononetin

Black cohosh (Actaea racemosa L. syn. Cimicifuga racemosa (L.) Nutt.), a North American perennial plant, is a promising natural alternative to hormone replacement therapy for treating menopausal symptoms, but the mechanism of action is not understood. The clinical actions of this plant have been attributed to the isoflavonone formononetin since 1985, when its presence was reported in a black cohosh extract. Others have since looked for formononetin, but have not detected it. We looked for formononetin in extracts of black cohosh roots and rhizomes collected in thirteen locations in the eastern United States, including Maryland, New Jersey, New York, North Carolina, Pennsylvania, Virginia, and Tennessee. The rhizome samples were extracted using 80% methanol, and the extracts were partially purified using solid-phase extraction to concentrate any isoflavonoids that might be present. We tested for formononetin in these partially purified samples using thin-layer chromatography and high-performance liquid chromatography with a photodiode array detector and a mass spectrometer. Formononetin was not detected in any of the thirteen plant populations examined. Remifemin, a German product now on the United States market, and CimiPure, a commercially available black cohosh rhizome extract, were also analyzed. We did not detect formononetin, or ononin (formononetin-7-glucoside), in any sample tested by the above-mentioned chemical analyses. Therefore, the clinically observed estrogen-like actions of black cohosh, such as reduction of hot flashes, are likely due to a compound, or combination of compounds, other than formononetin.

Complementary/alternative therapies for reducing hot flashes in prostate cancer patients: reevaluating the existing indirect data from studies of breast cancer and postmenopausal women

Vasomotor hot flashes are a common problem in women who are postmenopausal or receiving antiestrogen treatment for breast cancer. Hot flashes are also a common problem after orchiectomy/luteinizing hormone-releasing hormone therapy, occurring generally in 50% to 66% of these men. Prescribed treatments for hot flashes for men on hormonal ablation treatment for prostate cancer are well documented. These conventional agents have shown good results, but their long-term efficacy, safety, and cost are still questioned. Therefore, the search for other viable agents, including nontraditional treatments, continues. Complementary/alternative treatments to alleviate hot flashes in women have generated an enormous amount of interest. However, these options have received little attention in men with hot flashes. Research with vitamin E, soy, black cohosh, red clover, and numerous other alternative treatments in women may provide some indirect but valuable insight on their potential effectiveness in men. Many of these alternatives have been a disappointment in recent randomized trials of women, and it is likely that there will be similar results with men. However, numerous supplements have yet to be tested in a clinical trial against a placebo, and clinicians should become aware of this ever-increasing list. Patients should be made aware of the primary importance of lifestyle interventions that could partially affect hot flashes and immediately affect overall health, especially during the period of androgen suppression, when it is not uncommon to observe accelerated weight changes and insulin insensitivity. Otherwise, recent research with older and newer conventional agents, such as antidepressants or estrogen/progesterone, should be emphasized at this time for moderate-to-severe hot flashes that profoundly affect daily activities and/or sleep. Antidepressant supplements (St. John's wort) or acupuncture could also be an attractive option in future investigations. Low-dose estrogen seems particularly attractive, because it is inexpensive and may simultaneously reduce hot flashes and the risk of osteoporosis in men receiving long-term androgen suppression therapy; however, the potential for cardiovascular complications must be further investigated. Ultimately, adequate research (vs placebo) should determine the fate of the alternative supplements proposed for hot flash reduction.

Structure-function relationships of the raloxifene-estrogen receptor-alpha complex for regulating transforming growth factor-alpha expression in breast cancer cells

Amino acid Asp-351 in the ligand binding domain of estrogen receptor alpha (ERalpha) plays an important role in regulating the estrogen-like activity of selective estrogen receptor modulator-ERalpha complexes. 4-Hydroxytamoxifen is a full agonist at a transforming growth factor alpha target gene in situ in MDA-MB-231 human breast cancer cells stably transfected with the wild-type ERalpha. In contrast, raloxifene (Ral), which is also a selective estrogen receptor modulator, is a complete antiestrogen in this system. Because D351G ERalpha allosterically silences activation function-1 activity in the 4-hydroxytamoxifen-ERalpha complex with the complete loss of estrogen-like activity, we examined the converse interaction of amino acid 351 and the piperidine ring of the antiestrogen side chain of raloxifene to enhance estrogen-like action. MDA-MB-231 cells were either transiently or stably transfected with Asp-351 (the wild type), D351E, D351Y, or D351F ERalpha expression vectors. Profound differences in the agonist and antagonist actions of Ralcenter dotERalpha complexes were noted only in stable transfectants. The agonist activity of the Ralcenter dotERalpha complex was enhanced with D351E and D351Y ERalpha, but raloxifene lost its agonist activity with D351F ERalpha. The distance between the piperidine nitrogen of raloxifene and the negative charge of amino acid 351 was critical for estrogen-like actions. The role of the piperidine ring in neutralizing Asp-351 was addressed using compound R1h, a raloxifene derivative replacing the nitrogen on its piperidine ring with a carbon to form cyclohexane. The derivative was a potent agonist with wild type ERalpha. These results support the concept that the side chain of raloxifene shields and neutralizes the Asp-351 to produce an antiestrogenic ERalpha complex. Alteration of either the side chain or its relationship with the negative charge at amino acid 351 controls the estrogen-like action at activating function 2b of the selective estrogen receptor modulator ERalpha complex.

Applications of pulsed ultrafiltration-mass spectrometry

Pulsed ultrafiltration-mass spectrometry (PUF-MS) is a method with a variety of uses for the discovery and development of biologically active small molecules, including the screening of combinatorial libraries and natural product extracts for biologically active compounds, investigation of thermodynamic and kinetic ligand-receptor binding parameters, high-throughput metabolic screening, and the screening of combinatorial libraries and botanical extracts for electrophilic metabolites. Solution-phase ligand-screening assays that use pulsed ultrafiltration-mass spectrometry are useful for "reverse pharmacology" studies in which a macromolecular receptor of interest has been isolated, but ligands for the receptor are needed. Protein-binding studies that involve pulsed ultrafiltration can be used to rapidly determine classical binding parameters for interactions between a macromolecular receptor and a compound of interest. Metabolic screening assays can identify substrates for cytochromes p450, and should be capable of characterizing phase I metabolites with a throughput of at least 60 compounds/hr. Pulsed ultrafiltration can also be used in conjunction with LC-MS-MS to screen mixtures for compounds that might be activated metabolically to electrophilic quinoid and epoxide metabolites by cytochrome p450; that screening can provide early warning of compounds likely to be toxic when administered in large doses. The combination of pulsed-ultrafiltration extraction and mass spectrometric detection provides the sensitivity and selectivity necessary to characterize compounds present at low concentrations in complex chemical mixtures, and is applicable to the analysis of biologically active compounds from combinatorial libraries and botanical extracts.

Trifolium pratense (red clover) exhibits estrogenic effects in vivo in ovariectomized Sprague-Dawley rats

Studies were conducted using an ovariectomized rat model to determine the estrogenic and antiestrogenic activity of Trifolium pratense L. (red clover) extracts. A red clover extract, standardized to contain 15% isoflavones was administered by gavage [250, 500 and 750 mg/(kg x d)] to virgin, ovariectomized 50-d-old Sprague-Dawley rats, for 21 d in the presence and absence of 17beta-estradiol [50 microg/(kg x d)]. Estrogenic effects included an increase in uterine weight, vaginal cell cornification and mammary gland duct branching. Red clover produced a dose-dependent increase in uterine weight and differentiated vaginal cells at the two higher doses, but it did not stimulate cell proliferation in the mammary glands. Neither antiestrogenic nor additive estrogenic properties were observed in any of the tissues studied. These data suggest that red clover extract is weakly estrogenic in the ovariectomized rat model.

Estrogen depletion induces NaCl-sensitive hypertension in female spontaneously hypertensive rats

In women, arterial pressure generally increases after menopause, but several studies suggest that women who eat large amounts of plant estrogens (phytoestrogens) experience a slower rise in the incidence of postmenopausal hypertension. This suggests that both ovarian hormones (principally estrogen) and phytoestrogens may protect at least some women from hypertension. The present study tests the hypothesis that phytoestrogens blunt hypertension in estrogen-depleted female spontaneously hypertensive rats (SHR). Three-week-old ovariectomized SHR were fed one of four diets that contained basal (0.6%) or high (8%) NaCl with or without dietary phytoestrogens for 9 wk. In SHR on the basal NaCl diet, arterial pressure was unaffected by the removal of dietary phytoestrogens. In contrast, in SHR on the high-NaCl diet, arterial pressure was significantly higher in rats on the phytoestrogen-free (204 +/- 4 mmHg) compared with the phytoestrogen-replete (153 +/- 4 mmHg) diet. Ganglionic blockade resulted in reductions in arterial pressure that were directly related to the dietary NaCl-induced increases in arterial pressure. Together, these data indicate that dietary phytoestrogens protect ovariectomized female SHR from dietary NaCl-sensitive hypertension and that the sympathetic nervous system plays an important role in this effect. Furthermore, these results demonstrate that dietary phytoestrogens can have a major impact on the interpretation of studies into the physiological role of estrogen in females.

Analysis and screening of combinatorial libraries using mass spectrometry

Mass spectrometry is a highly selective and high throughput analytical technique that is ideally suited for the identification and purity determination of large numbers of compounds prepared using combinatorial chemistry or for the dereplication of natural products. Compounds may be characterized based on molecular weight, elemental composition and structural features based on fragmentation patterns. When coupled to a separation technique such as high-performance liquid chromatography (HPLC) or capillary electrophoresis, mass spectrometric applications may be expanded to include analysis of complex mixtures. However, the slower speed of the separation step reduces the throughput of the analysis. This review concerns the application of mass spectrometry to the characterization of combinatorial libraries and the screening of library and natural product mixtures. Strategies to enhance the throughput of LC-MS are discussed including fast HPLC and parallel LC-MS. Also, mass spectrometry-based screening methods are described including frontal affinity chromatography-mass spectrometry, gel permeation chromatography LC-MS, direct electrospray mass spectrometry of receptor-ligand complexes, affinity chromatography-mass spectrometry, and pulsed ultrafiltration mass spectrometry.