Chemical markers for quality control of bran-fried sulfur-fumigated Paeoniae Radix Alba.

In traditional Chinese medicine practice, crude herbs are often subjected to traditional processing (Paozhi in Chinese) for a special medicinal purpose. Bran-frying is one of processing methods for Paeoniae Radix Alba (PRA). Previous studies found that paeoniflorin and paeoniflorin sulfonate, a principle bioactive compound and its sulfur-fumigation induced characteristic sulfur-containing derivative, could be used together with sulfur dioxide residue as chemical markers for the quality control of sulfur-fumigated PRA crude material. In this paper, the feasibility of these three markers used for the quality control of bran-fried sulfur-fumigated PRA was further investigated. First, homemade samples of sulfur-fumigated PRA with different sulfur-fumigation duration (0.5-6 h) were bran-fried, and stored for 12 months. Second, the contents of sulfur dioxide residue, paeoniflorin and paeoniflorin sulfonate were dynamically quantified respectively. Third, the variation of the marker contents and their correlation during bran-frying and storage was evaluated. A validation was conducted using commercial bran-fried PRA samples. The results showed that bran-frying caused an averaged reduction of 20% in the content of sulfur dioxide residue, and during the first two months of storage the content of sulfur dioxide residue was decreased by up to 27%, then the content was tending towards stability for the subsequent ten months of storage (RSD = 3.92%). Meanwhile, paeoniflorin and paeoniflorin sulfonate were relatively stable, the contents of which were not affected by bran-frying processing and 12 months of storage. The correlations between the contents of sulfur dioxide residue and paeoniflorin/paeoniflorin sulfonate were obviously influenced by storage duration. Since sulfur dioxide residue is a safety marker, while paeoniflorin and paeoniflorin sulfonate can reflect the inner quality and the impact extent of sulfur-fumigation on the quality of bran-fried PRA respectively, these three chemicals might be used together as markers for the quality control, and consequently to ensure the safety and efficacy of bran-fried PRA.