Study on relationship between color characteristics of rhubarb charcoal in heating process and contents of 14 chemical components

Abstract

A method based on high performance liquid chromatography(HPLC) was developed for simultaneous content determination of 14 components in rhubarb charcoal. After 18 batches of raw rhubarb materials were heated at different temperatures and time points, the contents of 14 components(5 categories) were determined, including gallic acid, 5-hydroxymethylfurfural(5-HMF), 5 kinds of free anthraquinone, 5 kinds of bound anthraquinone and 2 kinds of sennosides. In the analysis of sample color characteristics combined with principal component analysis(PCA), it was found that 18 batches of samples can be grouped into five categories, with the traditional traits "black charred on the surface, dark brown inside" as the standard. Samples of category A, B, C and D were "less" carbonized, and category E samples were carbonized "moderately or a little bit excessively". The corresponding components sennoside and combined anthraquinone showed a one-way decreasing pattern, and the contents of free anthraquinone, gallic acid and 5-HMF showed an increasing pattern before decreasing. The results showed that the contents of free anthraquinone and gallic acid in the samples were larger than those in raw materials while the contents of glycosides and combined anthraquinone were lower than those in raw materials when the samples were "less" "moderately" or "a little bit excessively" carbonized. The two change modes of the component contents of the studied samples have good robustness, and have a reference value for more comprehensive evaluation and control of different heating conditions from the perspective of chemical characterization on the color and content of rhubarb charcoal and the change mode of the content of other carbon medicines.