[Mechanism for sperm immobilization activity of extract from Platycodon grandiflorum in vitro].
OBJECTIVE
To explore the mechanism of spermicidal effect of crude extract and platycodin-D from Platycodon grandiflorum (PG) root in vitro.


METHODS
Between February 2006 and December 2009, 38 fertile and healthy adult males were selected as donors. PG root was extracted and platycodin-D purified. Grouping was as follows: crude extract from PG root, platycodin-D, nonoxynol-9 (N-9, as a reference standard) and semen-added physiological saline (as control). Spermicidal experiments were carried out in vitro (Sander-Cramer test). The hypo-osmotic swelling (HOS) test and modified Eosin-Giemsa (EG) staining were used to detect the integrity of sperm membrane. Four types of sperm morphology were divided through HOS-EG test: Type A: spermatozoa with swelling in tails and head white staining HOS(+)-EG(-) (membrane intact); Type B: spermatozoa with no swelling in tails (membrane-damaged) and head white staining HOS(-)-EG(-); Type C: spermatozoa with tail swelling and head red HOS(+)-EG(+); Type D: spermatozoa with no swelling in tails and head red HOS(-)-EG(+). Sperm chromatin dispersion (SCD) test was performed to determine the integrity of sperm DNA.


RESULTS
The crude extract from PG root could immobilize and kill 100% spermatozoa within 20 s in vitro at the concentrations of 50.0 g/L and 20.0 g/L (v:v = 1:1 in semen). When the semen sample was exposed to the concentrations of 2.0 g/L and 1.0 g/L of platycodin-D, all spermatozoa were immobilized within 20 s. In the control group, the mean percentage of Types A, B, C and D was (69.0 ± 8.3)%, (3.4 ± 0.5)%, (10.2 ± 1.7)% and (17.4 ± 2.1)% respectively. In the groups of platycodin-D and N-9 solution, the rate of Types A and B was 0. The rate of Types C [(65.3 ± 3.8)%] and D [(34.7 ± 7.1)%] significantly increased versus control in the platycodin-D group (P < 0.01). Sperm DNA fragmentation had no change upon an exposure to the extract from PG root, platycodin-D and N-9 solution. And the sperm revival test showed none of the spermatozoa recovered their motility.


CONCLUSION
The extract and platycodin-D from PG root have a quick sperm-killing effect in a short time in vitro by disrupting the integrity of sperm membrane (main head).