Assay of free ferulic acid and total ferulic acid for quality assessment of Angelica sinensis.
Activity of Chinese Danggui (DG), the processed root of Angelica sinensis (Oliv.) Diels, is linked to the ferulic acid content but the stability of ferulic acid during extraction for medicinal use is not known. The stabilities of ferulic acid and coniferyl ferulate were evaluated in the extracts of DG using a variety of extraction solvents. These included various combinations and proportions of methanol, water, formic acid, 1 M aqueous hydrochloric acid and 2% sodium hydrogen carbonate (NaHCO3) in water. Coniferyl ferulate was found liable to hydrolyze into ferulic acid in neutral, strongly acidic and basic solvents, where heat and water could facilitate this hydrolysis. However, the hydrolysis was relatively resisted in weakly organic acid. Based on the stability evaluation, two new terms, namely: free ferulic acid and total ferulic acid, were suggested and defined. Free ferulic acid refers to the natural content of ferulic acid in herbs. Total ferulic acid means the sum of free ferulic acid plus the amount of related hydrolyzed components. Meanwhile, the high-performance liquid chromatographic (HPLC) method was developed to assay free ferulic acid and total ferulic acid in DG using methanol-formic acid (95:5) and methanol-2% NaHCO3 in water (95:5) as extraction solvents, respectively. Ten DG samples were investigated on their contents of free and total ferulic acid. The results indicated that the amount variety of free ferulic acid was larger than that of their counterparts, and the ratio of total ferulic acid to free ferulic acid was 4.07 +/- 2.73 (mean +/- SD, n = 10). The chemical assay of DG using total ferulic acid content would be a better choice to assess the herbal quality and was recommended.
Lu
Guang-Hua
GH
Research and Development Division, School of Chinese Medicine, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China.
Chan
Kelvin
K
Leung
Kelvin
K
Chan
Chi-Leung
CL
Zhao
Zhong-Zhen
ZZ
Jiang
Zhi-Hong
ZH
D029971:Angelica sinensis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003373:Coumaric Acids / Q000032:analysis* / Q000302:isolation & purification*; D004355:Drug Stability; D004365:Drugs, Chinese Herbal / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry; D011786:Quality Control; D015203:Reproducibility of Results
D003373:Coumaric Acids; D004365:Drugs, Chinese Herbal; C044571:coniferyl ferulate; C004999:ferulic acid