I am only marginally informed regarding this relatively new supplement called AntaGolin. I have not been able to find any medical studies using this supplekemt so I cannot remark on its effectiveness. Because there are no good medical studies with it, I cannot say with any confidence if this is completely safe. Any medication or supplement, particularly if it has not been subjected to FDA standards, should be taken with caution. Even "natural" substances can cause side effects, so please be careful.
Pre-diabetes is best managed with weight loss and diet changes. If you have other risk factors for diabetes, your doctor can consider starting you on Metformin. Perhaps you can seek a consultation with a nutritionist as a start.