Inhibitory effect of fermented papaya preparation on hydroxyl radical generation from methylguanidine

We have previously shown that extremely high level of guanidino compounds such as methylguanidine (MG), known as a neurotoxin and also a nephrotoxin, generate reactive oxygen species (ROS) using an electron spin resonance (ESR) technique with spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). In this in vitro study, the inhibitory effect of fermented papaya preparation (SAIDO-PS501:PS-501) on hydroxyl radical (.OH) generation from MG was examined using an ESR spectrometry, and it was found that PS-501 suppressed .OH generation from MG in a dose-dependent manner. The ID(50) value of PS-501 was 8 mg/ml. On the contrary, glucose itself did not suppress .OH generation from MG up to100 mg/ml, whereas PS-501 almost completely suppressed .OH generation from MG at a dose of 100 mg/ml. These results imply that PS-501 itself may have a beneficial effect of preventing ROS- and MG-related diseases.