Food-grade extraction and capsule formulation of genistein-rich soybean extract for nutraceutical applications

• A food-grade method in which ethanol and 5 N acetic acid were used to extract genistein from soybeans was developed. • A high yield of genistein (75.32 mg/100 g soybean powder) was achieved. • A stable genistein-rich powder with purified talcum as the excipient was prepared. • The powder showed good flowability and was formulated into oral capsules. • The capsules met the disintegration standards. The nutraceutical industry faces major challenges, as conventional genistein extraction relies on toxic solvents, which limits scalability and regulatory compliance. This study introduces a generally recognized as safe (GRAS) extraction paradigm using ethanol and food-grade acetic acid, offering a safer and more sustainable alternative. Through systematic pH optimization, 5 N acetic acid (used as a processing catalyst under controlled conditions) achieved the highest genistein recovery (75.32 mg/100 g soybean, approximately 15% higher than that of the methanol/HCl method and ∼83% higher than that of ethanol-only extraction). Additional profiling confirmed the presence of other isoflavones, including daidzein (18.6 mg/100 g) and glycitein (12.4 mg/100 g), broadening the bioactive composition. Powder manufacturing using pharmaceutical-grade talcum converted viscous extracts into free-flowing powders with optimal flow properties (e.g., angle of repose = 30.0°, compressibility index = 19.5%). The formulated capsules rapidly disintegrated (≤ 4 min), although weight variation failed to meet the pharmacopeial standards (observed deviation ±9–12%), highlighting the need for automated filling in scale-up. This methodology represents an alternative approach that offers scalable, environmentally sustainable, and regulatory-compliant options for genistein-based nutraceuticals. Future work must address stability testing, bioavailability studies, preliminary human pharmacokinetic assessments, and early-phase clinical validation strategies to confirm its clinical and industrial applicability.