Extracted directly from plants
Ferulic acid can be obtained from plants in three ways: one is obtained from the combination of ferulic acid and some small molecules, the other is obtained from plant cell walls, and the third is obtained through tissue culture. Ferulic acid in plants is mostly cross-linked with polysaccharides and lignin through ester bonds or self-esterified or etherified to form di-ferulic acid. Generally, the ester bond is broken by the alkali method and enzymatic method to release ferulic acid, and then a suitable solvent is used. to extract.
1. Alkaline hydrolysis method
The ferulic acid in the cell wall can be released by using 4% sodium hydroxide to react at room temperature for 24 hours under the condition of nitrogen flow. Recent studies have found that by increasing the extraction temperature and adding suitable protective agents, most of the ferulic acid in wheat bran can be released in a relatively short time. Using low concentration sodium hydroxide solution, most of the ferulic acid in wheat bran can be released at appropriate extraction temperature, and adding sodium sulfite during the extraction process can increase the recovery rate of ferulic acid. Due to the complex composition of lye, especially containing pigment substances, at present, the separation method of ferulic acid in lye is mainly by activated carbon adsorption. Oryzanol contains the structural unit of ferulic acid, exists in the form of an ester, and is easy to decompose, therefore, can first hydrolyze oryzanol with alkali, then prepare ferulic acid by the method of acidification, and the operation of its reactive hydrolysis oryzanol to prepare ferulic acid It is convenient, the yield is as high as 85.7%, and the by-products are pineapple alcohols. And oryzanol has a wide source, large output, and moderate price.
2. Ferulic acid esterase method
Ferulic acid esterase refers to an enzyme that can liberate ferulic acid from methyl ferulate, oligosaccharide ferulate, and polysaccharide ferulic acid. Fungi, bacteria, and yeast all secrete ferulic acid esterase. Using Aspergillus niger as a strain, a mixed enzyme preparation containing ferulic acid esterase and arabinoxylans was prepared by liquid submerged fermentation, and the mixed enzyme preparation was used to act on the de-starch wheat bran. The degradation rate of wheat bran was 55.46%.
3. Plant tissue culture method
Using the plant tissue culture method is an important way to obtain ferulic acid. Some studies have shown that certain plant tissue cultures can produce higher yields of ferulic acid derivatives. For example, the cell suspension culture of sugar beet and corn can obtain water-soluble glucosyl ferulate, sucrose ferulate, etc., and the content can be as high as 20.0 μmol/g callus (dry weight). In the direct extract, the content of ferulic acid is relatively low, and further purification is required.
The chemical synthesis method of ferulic acid uses vanillin as the basic raw material, and the main organic reactions used are the Wittig-Horner reaction and the Kneoevenagel reaction.
1. Synthesis of ferulic acid by Wittig-Horner reaction
Triethyl phosphite acetate and acetyl vanillin undergo Wittig-Horner reaction in a strong base system and then acidify with concentrated hydrochloric acid to obtain ferulic acid. This method needs to protect the phenolic hydroxyl group in advance, otherwise, due to the presence of a strong base, the formation of sodium phenolate will inhibit the reaction between the carbonyl group and the carbanion, and it is also prone to side reactions to generate impurities.
2. Kneoevenagel reaction to synthesize ferulic acid
A small amount of organic base is added to the pyridine solvent as a catalyst, and the Kneoevenagel reaction of vanillin and malonic acid occurs to generate ferulic acid. The catalysts include piperidine and aniline. However, the reaction time of this method is long, up to three weeks, and the obtained mixture is trans and cis ferulic acid.
The biosynthesis method uses several microorganisms to convert ferulic acid precursors into ferulic acids, such as eugenol cinnamate extracted from clove oil into ferulic acid. Biosynthesis is a clean and efficient synthesis method, but a method for mass production has not yet been developed.