Geographical-origin discrimination and volatile oil quantitative analysis of Zanthoxylum bungeanum Maxim. with a portable near-infrared spectrometer
Zanthoxylum bungeanum Maxim. (Z. bungeanum), widely grown in Asian countries, is a popular food additive and traditional Chinese medicine (TCM) in China. The aim of this study was to evaluate the applicability of a portable near-infrared (NIR) spectrometer for the quality control of Z. bungeanum. The portable NIR spectrometer was used to obtain the spectra of 75 samples from different origins. The reference values of the volatile oil content of Z. bungeanum were determined by the steam distillation method according to Pharmacopeia 2015. Based on linear discriminant analysis (LDA), a qualitative model for the geographical-region identification of Z. bungeanum was established. The qualitative analysis model was used to identify the origin of 75 samples and from these, the samples from the three origins could be clearly distinguished. Among these, the samples were discriminated with 96.67% rate of accuracy, and only two samples in the validation set were judged incorrectly. Moreover, a quantitative analysis model was established by using partial least square regression (PLSR) along with the reference value of the volatile oil content determined with a validated steam distillation method. For the built quantitative model, different approaches were used to pretreat the NIR spectra of the samples, and the results showed that the coefficient of determination (R2) of the validation set and the root mean square error of prediction (RMSEP) values of the optimal model were 0.81 and 0.46, respectively. In summary, all the results obtained from the qualitative and quantitative models demonstrated that the use of a portable NIR spectrometer could be considered as a rapid and effective way to perform the quality control of Z. bungeanum.