[Comparative study on composition and content of β-(1→3)-D-glucan in different medicinal parts of Poria cocos]

Poria cocos is a commonly used bulk traditional Chinese medicinal material, with multiple parts used medicinally, such as Poriae Cutis, Rubra Poria, White Poria, and Poria cum Radix Pini. Polysaccharides are their main active components. Clarifying the composition and content differences of polysaccharides in different medicinal parts of P. cocos can provide a reference for processing and clinical application of P. cocos medicinal materials and decoction pieces. In this paper, high-performance gel permeation chromatography(HPGPC) and nuclear magnetic resonance(NMR) spectroscopy were employed to qualitatively compare the relative molecular mass distribution and chemical composition of alkali-soluble polysaccharides from different parts of crude P. cocos. The results showed that the composition of alkali-soluble polysaccharides in Rubra Poria and Poriae Cutis was consistent with that in White Poria, all of which were β-(1→3)-D-glucans. The relative molecular mass distribution was also relatively close, ranging approximately from 9.13×10~4 to 1.04×10~5. On the basis of the content determination method of β-(1→3)-D-glucan in P. cocos according to the 2025 edition of Chinese Pharmacopoeia, the preparation method of the test sample solution was optimized. Firstly, a desalination step was added, which can enable the test sample chromatogram to present only the chromatographic peak of glucose, thereby reducing the difficulty of separation. Secondly, this experiment discovered for the first time that under acidic conditions, the hydrolysis of β-(1→3)-D-glucan to glucose was accompanied by the generation of a small amount of 5-hydroxymethylfurfural(5-HMF) as a by-product. A more intense acid hydrolysis reaction condition indicated a greater conversion yield of 5-HMF. Therefore, according to the results of single-factor experiments and response surface methodology experiments, the acid hydrolysis time was shortened from 6 h to 1.5 h, which improved the analysis efficiency. After verification, the optimized method was simple and stable, and had good repeatability and accuracy. Then, the optimized quantitative method was used to evaluate the content of β-(1→3)-D-glucan in different parts of crude P. cocos and decoction pieces. The results demonstrated that the content of β-(1→3)-D-glucan in different medicinal parts of P. cocos was in the order of White Poria, Poria cum Radix Pini, Rubra Poria, and Poriae Cutis. Among the commercially available Poria decoction pieces, the content of β-(1→3)-D-glucan in the white and hard decoction pieces was higher than that in the dark and loose-textured decoction pieces.