Abstract: In this study, the effects of NaOH concentration, liquid-to-solid ratio, ethyl acetate extraction time and extraction times on phenolic acid extraction from wheat were investigated. The extraction conditions were optimized by response surface methodology. A method based on high performance liquid chromatography-mass spectrometry (HPLC-MS) was used to quantify phenolic acid content in wheat grains varieties from different areas. The results showed that the concentration of NaOH, the ratio of liquid to solid, the extraction time of ethyl acetate and the times of extraction had significant effects on the extraction amount of phenolic acid from wheat grains. The optimum condition was: NaOH 1.56 mol/L, the ratio of liquid to material 15.52:1, the extraction time 17.33 min, and the extraction twice. Under this condition, the extraction amount of phenolic acids reached 1055.99 mg/kg. There are 9 kinds of phenolic acids in wheat, including gallic acid, protocatechuic acid, 4-hydroxybenzoic acid, vanillic acid, caffeic acid, eugenoic acid, p-coumaric acid, sinapic acid and ferulic acid. Ferulic acid is the main phenolic acid, accounting for73.07%-89.10% of the total phenolic acid in wheat varieties of this study. Ningmai 14 in Jianghuai area has the highest total phenolic acid content, with an average of 1001.12 mg/kg, and had the significant difference with Baomai No. 6 and Huaimai 33 in the sane area. The total phenolic acid content of Xinmai 26 in Huanghuai wheat area was the highest, with an average value of 1016.03 mg/kg, which was significantly different from that of Aikang 58 and Bainong 207 in this area. It can be seen that the difference of wheat varieties in different producing areas has great influence on phenolic acid content.

Key words: Wheat, phenolic acid, HPLC-MS, method optimization