This research shows that amphotericin B, a natural compound produced by bacteria, can effectively prevent gray mold from spoiling table grapes after harvest. The compound works by damaging the mold’s cell membranes and also activates the grapes’ own defense systems. At a treatment level of 200 mg/L, it completely prevented mold growth on grapes over a three-day storage period, offering a safer, more environmentally friendly alternative to synthetic fungicides.