Ferulic acid has anti-oxidation and anti-radiation properties. In this article, several methods for preparing ferulic acid will be introduced.
Direct extraction from plants
Ferulic acid can be obtained from plants in three ways: one is obtained from a combination of ferulic acid and some small molecules. The second is obtained from the plant cell wall. The third is obtained through tissue culture. In plants, ferulic acid is cross-linked with polysaccharides and lignin by ester bonds or self-esterified or etherified to form diferulic acid. Generally, the ester bond is used to release ferulic acid by alkali and enzymatic method, and then a suitable solvent is used. Perform extraction.
1. Alkaline solution
Ferulic acid in the cell wall can be released by reacting 4% sodium hydroxide at room temperature for 24 hours under nitrogen. Recent studies have found that most of the ferulic acid in wheat bran can be released in a relatively short period of time by increasing the extraction temperature and adding a suitable protective agent. Ou Shiyi and other low-concentration sodium hydroxide solution can release most of the ferulic acid in the wheat bran at the appropriate extraction temperature. The addition of sodium sulfite during the extraction process can increase the recovery rate of ferulic acid. Due to the complex composition of the lye, especially the pigment material, at present, the separation method of ferulic acid in the lye mainly adopts the activated carbon adsorption method. The structural unit containing ferulic acid in oryzanol exists in the form of ester and is easy to decompose. Therefore, it can be used to hydrolyze oryzanol with alkali, and then ferulic acid is used to prepare ferulic acid. The reaction method is to hydrolyze oryzanol to prepare ferulic acid. Convenient, the yield is up to 85.7%, and the by-product is ringwood pineapple alcohol.
2. Ferulic acid esterase method
Ferulic acid esterase refers to an enzyme that can release ferulic acid from methyl ferulate, oligosaccharide ferulic acid ester and ferulic acid. Fungi, bacteria and yeast all secrete ferulic acid esterase. Therefore, using Aspergillus niger as a strain, a mixed enzyme preparation containing ferulic acid esterase and arabinoxylanase was prepared by liquid submerged fermentation method, and a mixed enzyme preparation was applied to the de-starched wheat bran, and it was found to be degraded by 3 times. The degradation rate of post-wheat bran is 55.46%.
3. Plant tissue culture method
The use of plant tissue culture 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, cell suspension culture of sugar beet and corn can obtain water-soluble glucose ester of ferulic acid, sucrose ferulate, etc., and the content can be as high as 20.0unol/g.
Callus (dry weight). In the direct extract, the ferulic acid content is relatively low and further purification is required.
The chemical synthesis method of ferulic acid is based on vanillin. The main organic reactions are Wittig-Horner reaction and Kneoevenagel reaction.
1. Wittig-Horner reaction for the synthesis of ferulic acid
Triethyl phosphite acetate and acetyl vanillin undergo a Wittig-Horner reaction in a strong base system, and acidified with concentrated hydrochloric acid to obtain ferulic acid. This method requires pre-protection of the phenolic hydroxyl group. Otherwise, due to the presence of a strong base, the formation of sodium phenolate inhibits the reaction between the carbonyl group and the carbanion, and is also prone to side reactions to form impurities.
2. Synthesis of ferulic acid by Kneoevenagel reaction
A small amount of organic base is added as a catalyst in the pyridine solvent, and Kneoevenagel reacts with vanillin and malonic acid to form ferulic acid. The catalysts include piperidine and aniline. However, this method has a long reaction time of up to three weeks and is obtained as a mixture of trans and cis ferulic acid.
Biosynthesis is the conversion of ferulic acid precursor to ferulic acid by several microorganisms (Arthrobacter Blobiformis), such as the conversion of eugenol cinnamate extracted from clove oil to ferulic acid. Biosynthesis is a clean and effective synthetic method.
Separation and purification method
There are currently not many methods for purifying ferulic acid. There are mainly solvent extraction methods and adsorption methods.
1. Solvent extraction method
Commonly used solvents for extracting ferulic acid are mainly ethanol, ethyl acetate and the like. The principle is to extract ferulic acid in the extract by using a solvent having a high solubility to ferulic acid, and then distilling off the solvent under reduced pressure to obtain a ferulic acid product. The method is simple, but the yield is low and the energy consumption is large, which is the most commonly used method for purifying ferulic acid.
2. adsorption method
The adsorption method is a purification method which is currently studied more. The principle is that the ferulic acid in the solution is adsorbed and enriched by adding an adsorbent material, and then the adsorbed ferulic acid is eluted by an eluent. Couteau was screened from adsorption media such as activated carbon, polystyrene cross-linked resin, and PVPP. The study showed that activated carbon has a high adsorption capacity for ferulic acid (22 g per 100 g of adsorption), does not bind monosaccharide molecules, and is easy to elute. The advantage is the best adsorption medium. After the adsorption of activated carbon is completed, the adsorbed ferulic acid can be eluted with ethanol. In addition, activated carbon is also an excellent adsorbent material. After the extract is adsorbed by activated carbon, when the activated carbon reaches adsorption saturation, the pure ferric acid can be obtained from the extract by elution.
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