Abstract
Background/Objectives: Microcrystalline cellulose (MCC) is a commonly used pharmaceutical excipient. At present, the catalytic potential of MCCs for the degradation of active pharmaceutical ingredients (APIs) has not been paid adequate attention. This study aims to investigate the representativeness of the pH value of an MCC determined in accordance with the pharmacopeia method to the acidity on its surface. Methods: We tested the differences between the catalytic activities of different MCCs and their supernatant prepared in accordance with the pharmacopeia method for the hydrolysis of ginsenoside Re, which is relatively stable in neutral or weak alkaline aqueous solutions but sensitive to acid. The sulfur content of the sulfuric acid-prepared MCC was measured using an ICP-OES. Results: All of the five tested commercially available and two self-prepared MCCs have been found to significantly promote the hydrolysis of ginsenoside Re. But their supernatants were neutral and chemically inert to Re. The sulfur content of the MCC prepared in this experiment using sulfuric acid hydrolysis was determined to be 109.60 µg/g, which is equivalent to 186 to 465 µM of sulfuric acid on the surface. Conclusions: The pH value of an MCC determined in accordance with the pharmacopeia method is not representative of the acidity on its surface. The primary reason should be that there is immobilized acid that is not so easily dissociated into the media. Ginsenoside Re is sensitive and applicable as a probe for the evaluation of the catalytic potential of pharmaceutically used MCCs.