In vitro activity: Icariin inhibited the activity of PDE5 and PDE4 in a dose- andconcentration-dependent manner. The IC50of icariin on PDE5 was 0.43 μM and the IC50 on PDE4 was 73.50 μM. Icariin showed a selective inhibitory effect on cGMP-specific PDE5 compared to cAMP-specific PDE4. Icariincould also enhance the osteogenic differentiation of rat primary bone marrow stromal cells.

Cell Assay: Human umbilical vein endothelial cells (HUVECs) in the logarithmic growth phase are seeded into 96-well plates at a density of 1×104 cells per well, then incubated for 24 hours at 37°C, 5% CO2. After pretreatment with indicated concentration of Icariin (0, 10, 20, 40 μM) for 24 hours, the cells are incubated with or without ox-LDL (100 μg/mL) for next 24 hours. After suction of the liquid in the wells, MTT solution is added to yield a final concentration of 0.5 mg/mL, and incubation is continued for 4 h at 37°C, 5% CO2. MTT solution is removed gently and 150 μL of DMSO is added to each well for 15 min incubation. The absorbance of each sample is measrured on a microplate reader at 490 nm as cell viability.

Rats: Forty adult male SD rats weighing 200-290 g (12-16 weeks old) are randomly assigned to groups (n=10 per group) according to their body weight. The rats receive daily intragastric administration of Icariin at 0 (control), 50, 100, or 200 mg/kg per day for 35 consecutive days. The animals are weighed weekly, and the treatments are adjusted accordingly. At the end of the Icariin treatment period, all rats are sacrificed; blood samples are subsequently collected for further analyses of testosterone levels.