Valorization of Industrial Byproduct‑Rice Bran Acid Oil: Direct Extraction and Evaluation of Ferulic Acid and Phytosterols/Triterpene Alcohols for Cosmetic Applications

Purpose Rice bran acid oil (RBAO) is a free fatty acid-containing byproduct derived from the neutralization step of rice bran oil refnery. It is usually used as a low-value product for animal feed. Given the large amount of bioactive compound, γ-oryzanol, in the RBAO, there is the opportunity to redeploy RBAO as a source for other high-value products. The present study aims to develop a simple alkaline hydrolysis method that could concurrently produce ferulic acid (FA) and phytosterols/ triterpene alcohols (PTs) from the γ-oryzanol in the RBAO. The biological activities of FA and PTs were then evaluated for their suitability as cosmetic ingredients.

Methods The molar ratios of RBAO to KOH and the hydrolysis reaction time were investigated at 80 °C. The hydrolyzed products were chemically characterized by high-performance size-exclusion chromatography and were subsequently purifed to remove impurities. The biological activities including sun protection factor, antioxidant activity, tyrosinase inhibition and collagenase activities were evaluated.

Results The study shows that the RBAO to KOH ratio of 1:15 with 15 min reaction time gave the highest FA yield. The purifcation procedure resulted in FA and PTs purities of 96.93% and 90.23%, respectively. The FA demonstrated potent cosmetic properties (UV absorption, antioxidant activities, tyrosinase and collagenase inhibitory efects) that compared favorably with that of commercial FA. On the other hand, the PTs showed little activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals.

Conclusion This work presents a simple, fast and energy-efcient methodology for the simultaneous production of FA and PTs from RBAO. The RBAO-derived FA is suitable for cosmetic applications, while the PTs showed weak inhibitory activity on DPPH radicals