Cell experiment:

Primary rat osteoblasts are treated with 0.01-1 μM equol, 0.01-1 μM E2 , or 0.01-1 μM equol/E2 combined with 1 μM ICI182780 for 24 or 48 hours. Then 10 mL 5 mg/mL MTT solution is added to each well. The plates are incubated at 37℃ for 4 h, and then the supernatant is discarded and 100 mL DMSO is added to each well and mixed thoroughly before taking measurements in a microplate reader[3].

Animal experiment:

Rats: Equol or furosemide is administered orally at doses of 16, 40, and 100 mg/kg (in a volume of 16 mL/kg 5% arabic syrup) to groups of 3-9 rats (rats of a control group are administered vehicle only). Urine samples are collected for 6 h. Urinary sodium and potassium contents are measured by flame photometry[3]. Mouse: Equol is dissolved in water and administered orally to rats at a dose of 5 and 25 mg/kg BW for 8 weeks after a single dose of DMBA (100 mg/kg). As controls, rats are divided into vehicle alone and DMBA alone groups. In the second part, ICR mice are orally administered equol daily at a dose of 5 and 25 mg/kg BW for 7 weeks before a single dose of DMBA (34 mg/kg/week). After equol administration animals are followed for 1 week continuously. The control groups are the same as above and each group are comprised of six mice. Mice livers and mammary gland tumors are isolated, blotted, weighed, frozen in liquid nitrogen and stored at -70℃ until assayed[5].

IC50: Not available.

Equol is an isoflavan produced by intestinal bacteria in response to soy isoflavone intake in human. It shows a wide range of activities including antioxidant activity, anti-inflammation activity and anticancer activity. It is reported that Equol specifically binds to 5α-DHT and has a modest affinity for recombinant estrogen receptor ERβ, which may be responsible for most of Equol’s biological properties. [1]

In vitro: In vitro studies were conducted to measure both the binding affinity of Equol for 5alpha-dihydrotestosterone (5alpha-DHT) and the effects of Equol treatment in human prostate cancer (LNCap) cells. It was found that Equol bound to 5alpha-DHT with maximum and half maxim concentrations of 100 nM and 4.8 nM, respectively. In addition, Equol significantly offset the increases in PSA levels from LNCap cells. [1]

In vivo: An in vivo study was performed to investigate effects of equol on rat prostate weight and circulating levels of sex steroid hormones. 1.0 mg/kg of Equol was injected to Long-Evans rats fed with a low isoflavone diet for 25 days. Findings from this study suggested that Equol significantly decreased rat prostate weights and down-regulated serum levels of 5alpha-DHT. However, this agent did not alter levels of LH, testosterone and estradiol. [1]

Clinical trials: A clinical study on hypercholesterolemic patients demonstrated that, after 4 weeks’ dietary intervention with a soy isoflavone-containing food, brachial artery-mediated vasodilatation in equol-producers was notably higher when compared with that in equol-nonproducers. Similar differential effects between equol-producers and nonproducers were aslo reported in arterial stiffness from a study on postmenopausal women taking tibolone. [2]

References:
[1]Lund TD, Blake C, Bu L, Hamaker AN, Lephart ED.  iEquol an isoflavonoid: potential for improved prostate health, in vitro and in vivo evidence. Reprod Biol Endocrin. 2011; 9(4): doi: 10.1186/1477-7827-9-4.
[2]Setchell DR and Clerici C.  Equol: Pharmacokinetics and biological actions. J Nutr. 2010 Jul; 140(7): 1363S–8S.