**Soy Isoflavone Genistein Inhibits an Axillary Osmidrosis Risk Factor ABCC11: In Vitro Screening and Fractional Approach for ABCC11-Inhibitory Activities in Plant Extracts and Dietary Flavonoids**

**Hiroki Saito 1,2,**†**, Yu Toyoda 2,\*,**†**, Hiroshi Hirata 1, Ami Ota-Kontani 1, Youichi Tsuchiya 1, Tappei Takada 2 and Hiroshi Suzuki 2**


Received: 2 July 2020; Accepted: 12 August 2020; Published: 14 August 2020

**Abstract:** Axillary osmidrosis (AO) is a common chronic skin condition characterized by unpleasant body odors emanating from the armpits, and its aetiology is not fully understood. AO can seriously impair the psychosocial well-being of the a ffected individuals; however, no causal therapy has been established for it other than surgical treatment. Recent studies have revealed that human ATP-binding cassette transporter C11 (ABCC11) is an AO risk factor when it is expressed in the axillary apocrine glands—the sources of the o ffensive odors. Hence, identifying safe ways to inhibit ABCC11 may offer a breakthrough in treating AO. We herein screened for ABCC11-inhibitory activities in 34 natural products derived from plants cultivated for human consumption using an in vitro assay system to measure the ABCC11-mediated transport of radiolabeled dehydroepiandrosterone sulfate (DHEA-S—an ABCC11 substrate). The water extract of soybean (*Glycine max*) was found to exhibit the strongest transport inhibition. From this extract, via a fractionation approach, we successfully isolated and identified genistein, a soy isoflavone, as a novel ABCC11 inhibitor with a half-maximal inhibitory concentration value of 61.5 μM. Furthermore, we examined the e ffects of other dietary flavonoids on the ABCC11-mediated DHEA-S transport to uncover the e ffects of these phytochemicals on ABCC11 function. While further human studies are needed, our findings here about the natural compounds will help develop a non-surgical therapy for AO.

**Keywords:** axillary osmidrosis treatment; bioactivity investigation of food extract; body odor; food ingredient; functional food; *Glycine max*; health promotion; MRP8; phytochemicals; transporter
