# A Method for Ferulic Acid Production from Rice Bran Oil Soapstock Using a Homogenous System
## 1 Introduction  
Ferulic acid (FA) is an antioxidant widely used in the cosmetic industry applied in terms of Ultraviolet (UV) protection and to protect against various inflammatory diseases [1]. It also reduces the cholesterol levels in serum and liver, protects against coronary disease, and acts as antimicrobial and anti-inflammatory agents [2]. On the other hand, FA has been investigated for blocking the formation of nitrosamine from nitrites both in vitro and in vivo in humans and mice [3]. Besides, FAalso helps to prevent e.g., cardiovascular disease, diabetes, Alzheimer's, colon cancer and reduces blood cholesterol [2; 4; 5; 6; 7; 8; 9].  
FA is an ubiquitous phenolic compound in plant tissues such as citrus fruits, bananas, eggplant, cabbage, beetroot, broccoli, coffee [1; 10], corn bran, rice bran, flax shives, wheat [11], paddy straw [12], _Radix Angelicae sinensis_[13], and _Ligusticum chuanxiong_[14]. In cereal, FA is located in the bran. It also exists in ester forms such as steryl ferulates (\(\gamma\)-oryzanol), which was firstly recognized in 1954 in rice bran oil (RBO). \(\gamma\)-Oryzanol is a mixture of ferulate compounds, of which the four main ferulates are cycloartenyl ferulate, 24-methylene-cycloartenyl ferulate, campesteryl ferulate and \(\beta\)-sitosterolyl ferulate. Rice bran is unique source of \(\gamma\)-oryzanol [15]. In rice refining and processing, 96% of the \(\gamma\)-oryzanol contained in rice bran has been discarded as the by-products [16].  
The preparation of FA from RBO soapstock has received much attention, particularly in rice-producing countries such as India, China, Japan, Thailand, and the United States. One of patents on the FA manufacturing process has been filed by the TSUNO company (Japan) [17]. The process for FA production was as follows: alkaline hydrolysis of crude \(\gamma\)-oryzanol (purity 80%, 10 g), base catalyst of NaOH (5 g), water (20 mL), and solvent of isopropanol (20 g). Using the method, a molar yield of FA of 86% was obtained at 90 \({}^{\circ}\)C in 8 h. There have been many reports of the use of ultrasound irradiation to accelerate reactions and extraction [18; 19; 20; 21; 22; 23; 24]. However, no reports were found regarding the effect of ultrasound on hydrolysis of \(\gamma\)-oryzanol.  
Asian countries have the biggest capacity for rice production in the world. In Vietnam, the total amount of rice bran produced is about three million tons per year, but the potential inherent value of rice bran has not been fully exploited. In 2003, the first Vietnamese factory for RBO production with a capacity of 500 tons per day [25] was constructed in Can Tho City. The production of FA from \(\gamma\)-oryzanol contained in RBO soapstock is a promising manufacturing.  
In this study, we examined the FA production from \(\gamma\)-oryzanol standard using alkaline catalyst of potassium hydroxide (KOH) with homogeneous solvent (water/EtOH/EtOAc) system, and by assistance of ultrasonic irradiation. In order to obtain high yield of FA, the experiments were conducted by varying the parameters as follows: the initial concentrations of \(\gamma\)-oryzanol, the ratios of KOH to \(\gamma\)-oryzanol (\(\underline{wt}/\underline{wt}\)), the ratios of solvent EtOH to EtOAc (\(v/v\)), ultrasound frequencies, reaction temperatures, and the duration of reaction. The method developed was applied to hydrolysis of the \(\gamma\)-oryzanol-containing extracts (Ory-extract) from RBO soapstock. The _trans-cis_ isomerization of ferulic acid in the mixture after reaction was explored during one-month storage.