Table 2. PDE5 inhibition by ICA /ICA derivatives and mechanism.
| ICA and ICA derivative | Year of publication | Study type | Mechanism of PDE5 inhibition | The inhibition Effect for PDE5 | Key reference |
|---|---|---|---|---|---|
| ICAII | 2006 | In vitro (crystal structure and enzyme kinetics) | Bonding with PDE5A1 flexible H-loop | Selectively inhibiting PDE5A1 with an IC50 of 2M | (29) |
| ICA derivative-Compounds 3 | 2019 | In vitro (crystal structure and enzyme kinetics) | The hydrophobic group at the 3-o position more significantly inhibiting PDE5 | Inhibiting PDE5 with an IC50 of 0.083±0.01 μM | (30) |
| ICA | 2003 | In vitro (enzyme kinetics) | – | Inhibiting PDE5 with an IC50 of 0.432 µM | (31) |
| ICA | 2006 | In vitro (rat cavernous smooth muscle cells and enzyme kinetics) | – | Inhibiting PDE5A1, A2, and A3 with an IC50 value of 1.0, 0.75, and 1.1 M | (32) |
| ICAII | 2012 | In vitro (rat corpus cavernosum tissue and enzyme kinetics) | – | about 50% of Sildenafil | (33) |
| 3,7-bis(2-hydroxyethyl) Icaritin | 2008 | In vitro (enzyme kinetics) | – | With a similar IC50 to that of sildenafil (IC50 75 vs. 74 nM) | (34) |
| ICA | 2006 | In vitro (rat corpus cavernosum tissue and enzyme kinetics) | Inhibit PDE5 mRNA expression | Inhibiting PDE5 with EC50 was 4.62 micromol/L | (35) |
| ICA | 2014 | In vivo (rat corpus cavernosum tissue and enzyme kinetics) | Inhibit PDE5 expression | – | (36) |
PDE5, phosphodiesterase type 5; ICA, icariin; ICAII, icariside II; IC50, the half maximal inhibitory concentration; EC50, concentration for 50% of maximal effect.