Effects of Alpinumisoflavone and Abyssinone V-4′- Methyl Ether Derived from Erythrina lysistemon (Fabaceae) on the Genital Tract of Ovariectomized Female Wistar Rat M.A. Mvondo, 1 D. Njamen, 1 * S. Tanee Fomum 2 and J. Wandji 2 1 Department of Animal Biology and Physiology, Laboratory of Animal Physiology, University of Yaounde I, P.O. Box 812 Yaounde, Cameroon 2 Department of Organic Chemistry, University of Yaounde I, P.O. Box 812 Yaounde, Cameroon Erythrina lysistemon is an African medicinal plant used as a palliative for problems in women. The crude extract of this plant was shown to exhibit estrogenic effects on the female rat reproductive tract and on cell cuture. Using classic chromatographic methods, two compounds have been isolated as major constituents of this extract: alpinumisofl avone (1) and abyssinone V-4′-methyl ether (2). To determine whether both compounds are actives principles accounting for E. lysistemon effects, we applied the classic 3-day uterotrophic assay. We also carried out a ligand binding assay to determine whether the observed effects are estrogen receptor (ER) mediated. This study showed that whereas compound 1 displayed a fourfold preference for ERa, compound 2 bound ERa and ERb with a same affinity. The in vivo study showed that compound 1 increased the uterine wet weight by 182.23% ( p < 0.01) and 71.79% ( p < 0.05) at doses of 0.1 and 1 mg/kg BW/day respectively. The uterine epithelium thickened dose-dependently. Vaginal epithelial height also increased by 369.97 and 226.76% respectively (p < 0.01). Compound 2 acted only on the vagina and increased vaginal epithelial height by 244.56% ( p < 0.01) at 1 mg/kg BW/day. These results suggest that compounds 1 and 2 are endowed with estro- genic properties accounting, at least in part, for E. lysistemon effects. Copyright © 2011 John Wiley & Sons, Ltd. Keywords: estrogenicity; estrogen receptor ligands; ovariectomy; vaginal stratification; uterine growth. INTRODUCTION Estrogens, especially 17b-estradiol, are pleiotropic go- nadal steroids that affect many physiological functions including reproduction, bone metabolism, the cardio- vascular system and brain function (Böttner et al., 2006). Menopause marks the end of the reproductive life span of women and is characterized by a dramatic drop in circulating estrogens. Symptoms associated with estrogen deprivation include vasomotor instabil- ity (hot flushes), genito-urinary atrophy, osteoporosis and depression. Hormone replacement therapy (HRT) has been successfully used to treat the symp- toms of menopause because estrogen has strong suppressive effects on climacteric complaints. Recent studies, however, have uncovered a greater under- standing of the hazards of HRT. The Women’s Health Initiative Study was abandoned because several ad- verse effects, including higher risk for breast cancer and coronary heart disease, outweighed the benefits of hormone treatment for postmenopausal women (Derry, 2004). Similar results were obtained from the ‘Million Women Study’ (Beral, 2003). These findings led to various attempts to search for alternatives to classic HRT and plant-derived phytoestrogens might be the candidates. Phytoestrogens are compounds found in plants and fungi that exhibit estrogenic activity both in vivo and in vitro. The scientific interest lies in the potential of phytoestrogens for medical use either as a registered drug or mostly as a dietary supplement. Kaufert et al. (1998) reported that 80% of women aged 45–60 years were using non-prescription therapies to manage meno- pausal symptoms. More recently, Ferrari (2009) reported that in daily practice conditions, high doses of isoflavones, particularly genistein, can be used for the management of hot flushes in postmenopausal women not treated with HRT due to their early onset of action, efficacy and safety. Nevertheless, the effectiveness of phytoestrogens on breast cancer, cardiovascular dis- eases and bone health is still controversial (Wuttke et al., 2007). Therefore, there are efforts to find new compounds that exert selective effects by acting as an estrogen receptor (ER) antagonist on neoplastic or normal breast and uterine tissues, and as an ER agonist on estrogen-dependent tissues such as bones, liver and the central nervous system. In this search, the science of ethnobotany and pharmacognosy are being used as a guide towards different sources and classes of com- pounds and the tropical flora, by virtue of its diversity, continues to provide new leads. Erythrina lysistemon is a medicinal plant widely dis- tributed in South Africa and traditionally used as antibacterial, antiinflammatory, analgesic medicine and * Correspondence to: Dieudonné Njamen, Department of Animal Biology and Physiology, Laboratory of Animal Physiology, University of Yaounde I, P.O. Box 812 Yaounde, Cameroon. E-mail: dnjamen@gmail.com PHYTOTHERAPY RESEARCH Phytother. Res. (2011) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/ptr.3685 Copyright © 2011 John Wiley & Sons, Ltd. Received 05 September 2011 Accepted 18 September 2011