Effects of Ginseng Rhizome and Ginsenoside Ro on Testosterone 5α-Reductase and Hair Re-growth in Testosterone-treated Mice.

Murata K, Takeshita F, Samukawa K, Tani T, Matsuda H

Faculty of Pharmacy, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka, 577-8502, Japan.

This research program on the novel functions of Panax ginseng C. A. Meyer focused on the effects of ginseng rhizome on hair re-growth in androgenetic alopecia. Extracts of red ginseng rhizome showed greater dose-dependent inhibitory effects against testosterone 5α-reductase (5αR) when compared with extracts of the main root. Ginsenoside Ro, the predominant ginsenoside in the rhizome, and ginsenoside Rg(3) , a unique ginsenoside in red ginseng, showed inhibitory activity against 5αR with IC(50) values of 259.4 and 86.1 µm, respectively. The rhizome of P. japonicus, which contains larger amounts of ginsenoside Ro, also inhibited 5αR. Topical administration of extracts of red ginseng rhizomes (2 mg/mouse) and ginsenoside Ro (0.2 mg/mouse) to shaved skin inhibited hair re-growth suppression after shaving in the testosterone-treated C57BL/6 mice. These results suggest that red ginseng rhizomes containing both oleanane- and dammarane-type ginsenosides are a promising raw material for cosmetic use. This is the first report that ginsenoside Ro enhances in vivo hair re-growth based on their inhibitory activity against 5αR in the androgenetic alopecia model. Copyright © 2011 John Wiley & Sons, Ltd.

Published 3 May 2011 in Phytother Res.
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This is pretty exciting.

Extracts of red ginseng rhizome showed greater dose-dependent inhibitory effects against testosterone 5α-reductase (5αR) when compared with extracts of the main root.

I wonder what's meant by "testosterone 5α-reductase"?

Topical administration of extracts of red ginseng rhizomes (2 mg/mouse) and ginsenoside Ro (0.2 mg/mouse) to shaved skin inhibited hair re-growth suppression after shaving in the testosterone-treated C57BL/6 mice.

What was the mechanism for hair growth suppression? Was it androgen-induced suppression?