Rapid Identification of the Quality of Eucommiae Cortex During the Whole Process of Salt Processing Based on Chromaticity and Near-Infrared Spectroscopy

Background As one of the traditional Chinese medicines, Eucommiae Cortex (EC) was often prepared with salt in the clinic to enhance its efficacy. However, its processing degree had always been judged by "experience," and the quality of EC decoction pieces after processing could not be accurately controlled.Objectives This study aims to establish a qualitative model and a quantitative model in the salting process of EC, which could quickly determine its processing degree and internal quality.Materials and Methods First, determine the chromaticity values and the contents of geniposidic acid, chlorogenic acid, geniposide, pinoresinol diglucoside, and hyperoside in 123 batches of differently processed EC, and analyze their correlations. The results showed that the chromaticity values had different degrees of correlation with the components. The orthogonal partial least squares discriminant analysis (OPLS-DA) method was used to establish the chromaticity qualitative discriminant model and the near-infrared (NIR) qualitative discriminant model. The two qualitative models well distinguished the samples of four categories: raw EC, processing less, salt eucommia, processing too much, and the model verification results were good. Finally, an NIR quantitative model was established by using the partial least squares (PLS) method, combined with chroma value, content, and NIR spectroscopy.Results There were different degrees of correlation between the chromaticity values and the components. The qualitative and quantitative discriminant models established were good enough to distinguish the four types of samples: raw eucommia, insufficient processing, salt eucommia, and excessive processing, and the model verification results were good.Conclusions The intrinsic characteristic component content and chroma value of EC in the salting process could be predicted simultaneously by the model, which provided a rapid determination method for the quality control of EC in the processing process.