Purification, characterization, and cellular antioxidant activity of 4,4‐dimethylsterols and 4‐desmethylsterols

A mixture of 4,4‐dimethylsterols (TA) and 4‐desmethylsterols (PS) was produced as valuable byproducts during the large‐scale production of ferulic acid by γ‐oryzanol. However, the utilization of both byproducts is impeded by this mixed form. This study has developed a novel method for separating TA and PS through a one‐step separation procedure using flash chromatography. The optimal conditions were as follows: mobile phase of hexane‐ethyl acetate (9:1, vol/vol), the flow rate of 40 ml/min, loading volume of 20 ml, run time of 20 min. Under optimized conditions, TA with a yield of 41.8% ± 2.8% with a purity of 93.4% ± 0.4% was obtained, and 36.8% ± 1.7% and 98.2% ± 0.8% for that of PS. Their chemical structures were further confirmed by ultraviolet spectroscopy (UV), Fourier‐transform infrared spectroscopy (FT‐IR), and gas chromatography–mass spectrometry (GC–MS). The time‐fluorescence value curve indicated that TA and PS had inhibitory effects on peroxyl radical‐induced 2′,7′‐dichlorofluorescin (DCFH) oxidation. The results showed that TA had higher cellular antioxidant activity (CAA) than PS. TA was more suitable as a potential natural antioxidant. The present study provides a convenient method for high‐purity TA and PS production, which will improve the value‐added byproducts from the large‐scale production of ferulic acid.