Distribution profiles of 12 isoflavone monomers in Chinese soybeans from saline-alkali and ordinary soils and subsequent supercritical CO₂ extraction optimization.

Soy isoflavones are bioactive compounds with multiple physiological benefits, and saline-alkali-grown soybeans represent a promising underutilized resource. This study analyzed 12 isoflavone monomers in 69 soybean samples from ordinary/saline-alkali soils. Cultivated soybeans from saline-alkali soil had a slightly higher median content (2550 mg/kg) than those from ordinary soil (2422 mg/kg). Wild soybeans from saline-alkali soil showed higher accumulation (4025 mg/kg) with a much higher proportion of bioactive aglycones (12.5% vs. 0.76% in cultivated). However, the small sample size and the absence of ordinary soil controls make these findings preliminary. Furthermore, supercritical CO₂ extraction was optimized via single-factor experiments and response surface methodology using wild soybeans. Optimal conditions (35 MPa, 49 °C, 1.85 h, 30 mesh, and 1,4 g/mL) yielded 1607 mg/kg isoflavones, with the aglycone yield increasing by 7.4 times and solvent consumption decreasing by 84.6%. These findings suggest that saline-alkali soybeans are valuable resources, and the green extraction method supports their high-value utilization in functional foods.