Riboflavin is a water-soluble B vitamin essential for energy metabolism, acting as a precursor to FMN and FAD coenzymes in redox reactions. It is yellow-orange crystalline, stable to heat but sensitive to light. Found in dairy, eggs, and leafy greens. Niacin (B3) is separate with different properties; this data focuses on riboflavin as primary example. Supports cellular respiration and antioxidant activity via glutathione reductase.