Promotion of Hair Growth by Rosmarinus officinalis Leaf Extract

Topical administration of Rosmarinus officinalis leaf extract (RO‐ext, 2 mg/day/mouse) improved hair regrowth in C57BL/6NCrSlc mice that experienced hair regrowth interruption induced by testosterone treatment. In addition, RO‐ext promoted hair growth in C3H/He mice that had their dorsal areas shaved. To investigate the antiandrogenic activity mechanism of RO‐ext, we focused on inhibition of testosterone 5α‐reductase, which is well recognized as one of the most effective strategies for the treatment of androgenic alopecia. RO‐ext showed inhibitory activity of 82.4% and 94.6% at 200 and 500 µg/mL, respectively. As an active constituent of 5α‐reductase inhibition, 12‐methoxycarnosic acid was identified with activity‐guided fractionation. In addition, the extract of R. officinalis and 12‐methoxycarnosic acid inhibited androgen‐dependent proliferation of LNCaP cells as 64.5% and 66.7% at 5 µg/mL and 5 μM, respectively. These results suggest that they inhibit the binding of dihydrotestosterone to androgen receptors. Consequently, RO‐ext is a promising crude drug for hair growth. Copyright © 2012 John Wiley & Sons, Ltd.