Estrogenic and safety evaluation of root extract of Millettia aboensis as a potential plant derived alternative for hormone replacement therapy

Poor compliance with conventional estrogen replacement therapy due to associated side effects has led to the need for alternative therapeutic intervention to mitigate the symptoms and diseases associated with menopause. This study investigated the estrogenic effect of root extract of M. aboensis (MA) as a potential plant derived alternative for hormone replacement therapy (HRT). Phytoestrogen content of the methanol root extract and its solvent fractions was determined using genistein as standard. Further characterization of the phytoestrogen rich fraction (PRF) was done using HPLC-DAD. Acute toxicity of the extract was determined across oral doses of 100–5000 mg/kg while its effective dose (ED₅₀) was tested at doses ranging from 100–1600 mg/kg using vaginal cytology as an index of estrogenicity. Uterotrophic effect, serum estradiol quantification, liver and kidney toxicities were tested following 30 days treatment of ovariectomized female rats with PRF. The LD₅₀ of the extract was estimated to be >5000 mg/kg while the ED₅₀ was calculated to be 321.58 mg/kg. The ethyl acetate fraction showed the highest phytoestrogen content of 115 mg genesteinEq/g. HPLC-DAD analysis of this fraction identified these phytoestrogens as 9-alpha-OH-pinoresinol, isoprunetin 8C glucoside, daidzin, genistein 6C glucoside and Neobavaisoflavone. At 200 mg/kg, PRF showed serum estradiol level of 3.16 pg/mL against 0.25 and 5.82 pg/mL shown by the vehicle and estradiol control groups respectively. Administration of PRF showed a dose dependent weekly increase in vaginal cornification. Treatment with 1 mg/kg estradiol valerate and 400 mg/kg PRF significantly (p < 0.05) increased the uterine weight compared to OVX control. However, at 200 mg/kg, PRF was unable to produce significant increase compared to OVX control. Estradiol control showed significantly (P < 0.05) higher increase in uterine weight (0.153 mg/100 g body weight) than the 200 mg/kg PRF fraction (0.025 mg/100 g body weight). The PRF administration confers significant (P < 0.05) protection of the liver and kidney against ovariectomy induced organ damage. The weak uterotrophic effect and wide margin of effective and toxic doses of PRF of MA supports its use as alternative to HRT .