**5. Conclusions**

In conclusion, we found that the soybean extract inhibits the transport activity of ABCC11. From this extract, we successfully identified genistein, a compound known to be fairly safe for humans, as an active ingredient. Additionally, to the best of our knowledge, the present study is the first one demonstrating that some dietary flavonoids can inhibit ABCC11, at least in vitro. While human studies are needed to examine the effects of ABCC11-inhibitory phytochemicals on the AO phenotype, our findings here may provide a new clue for treating AO.

**Author Contributions:** Conceptualization, Y.T. (Yu Toyoda), H.H., and T.T.; data curation, H.S. (Hiroki Saito), Y.T. (Yu Toyoda), and H.H.; formal analysis, H.S. (Hiroki Saito) and Y.T. (Yu Toyoda); funding acquisition, Y.T. (Yu Toyoda); investigation, H.S. (Hiroki Saito), Y.T. (Yu Toyoda), H.H., and A.O.-K.; methodology, H.S. (Hiroki Saito), Y.T. (Yu Toyoda), and H.H.; project administration, Y.T. (Yu Toyoda) and H.H.; supervision, Y.T. (Youichi Tsuchiya) and H.S. (Hiroshi Suzuki); validation, H.S. (Hiroki Saito), Y.T. (Yu Toyoda), and T.T.; visualization, Y.T. (Yu Toyoda) and H.H.; writing—original draft, Y.T. (Yu Toyoda) in consultation with H.S. (Hiroki Saito) and H.H.; writing—review and editing, Y.T. (Yu Toyoda) and T.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by JSPS KAKENHI Grant Number 19K16441 (to Y. Toyoda).

**Acknowledgments:** The authors thank Naoyuki Kobayashi for his continuous encouragemen<sup>t</sup> and support for this study, and Chie Umatani for her reviewing our manuscript and technical support for visualization.

**Conflicts of Interest:** H. Saito, H.H., A.O.-K., and Y. Tsuchiya were the employees of Sapporo Holdings Ltd.; H. Saito, Y. Toyoda, H.H., A.O.-K., T.T. and H. Suzuki have a patent pending related to the work reported in this article.
