Androgenetic alopecia is characterized by the gradual miniaturization of hair follicles (vellus hair) resulting from the decrease in the duration of anagen phase. 

Thus, the anagen elongation is thought to be the most effective for the improvement of androgenetic alopecia. In the course of screening plant extracts for anagen elongation activity, the extract of dried roots of Sophora Flavescens Aiton (SRE), which is well-known as a Chinese traditional medicine, was found to possess potent anagen elongation activity using human hair follicle organ culture. 
When anagen hair follicles were cultured in Williams E medium in the presence of SRE, hair shaft elongation was significantly accelerated compared with those cultured in the absence of SRE. In anagen hair follicles, the proliferating cells are distributed in epithelial cells, such as hair matrix cells and outer root sheath cells (ORSC). The elongation of anagen phase was estimated by growth stimulation of hair follicle epithelial cells. 

We used a serum-free culture system of human ORSC to estimate the effect of anagen elongation. When human ORSC was cultured in the presence of SRE, one ppb of dry residue was sufficient for the growth stimulation of ORSC. These results suggest that SRE is effective for anagen elongation because of the stimulation of the proliferation of hair follicle epithelial cells. In order to isolate active compound for anagen elongation, SRE was fractionated by solvent extraction and subsequent silica gel chromatography. 
The hydrophobic fraction showed activity for ORSC growth stimulation. Further purification showed two independent active compounds. When their structures were elucidated using NMR and FAB-MS method, these were two pterocarpan derivatives, medicarpin and maakiain, and exhibited significant acceleration of ORSC proliferation.