Plant polyphenols possess diverse medicinal and therapeutic properties. For instance, they can prevent such age-related diseases as stroke, heart attack, type II diabetes, and their various pathological complications. Mangiferin is a polyphenolic compound with a C-glycosylxanthone structure. This biologically active substance is known for its antioxidant, anti-inflammatory, antimicrobial, antidiabetic, and immunomodulatory properties. This research features mangiferin isolated fromHedysarum neglectumL. root culture and its effect on fat accumulation inCaenorhabditis elegansN2 Bristol. A set of experimentsin vivoproved that mangiferin was able to inhibit fat accumulation in the model organism. The optimal concentration was determined as 50 μm: it provided 44.5% fluorescence.