Comparative analysis of rapid quality evaluation of Salvia miltiorrhiza (Danshen) with Fourier transform near-infrared spectrometer and portable near-infrared spectrometer

Abstract The root of Salvia miltiorrhiza, has wide applications in clinical practice such as the treatment of cardiovascular and cerebrovascular diseases. Due to the diversity of geographical origins and difference in quality, rapid and nondestructive methods such as near infrared spectroscopy (NIRS) technique for quality analysis are highly needed. Besides, because of its portability, the portable near-infrared spectrometer is suitable for the on-site detection of Chinese medicinal materials. It is not clear how far its performance differs from conventional analytical-grade NIR spectrometers. Therefore, in this study, a Fourier transform near-infrared spectrometer and a portable near-infrared spectrometer were both employed and compared in developing a rapid and nondestructive method for discrimination of geographical origins, determination of four active components (ACs, including tanshinone II A, cryptotanshinone, tanshinone I and salvianolic acid B) and evaluation of antioxidant activity (AA) in vitro. The geographical origins were discriminated by using partial least squares-discriminant analysis (PLS-DA) and the satisfactory discrimination results can be obtained by both instruments. PLS regression was applied to establish the quantification models for ACs and AA by NIRS. The correlation coefficients in the prediction set (Rp2) of Fourier transform near-infrared spectroscopy (FT-NIRS) for all ACs were above 0.93 with small prediction error and residual prediction deviation (RPD) values all greater than 3. While, the micro near-infrared spectroscopy (MicroNIRS) models performed slightly worse: the Rp2 values for most components can reach 0.92 with RPD values higher than 3, which was still enough for prediction, but for cryptotanshinone, the prediction error was larger and it may be difficult to guarantee accurate prediction results with limited samples. In the prediction of AA, since the reference values of AA were influenced by reaction contingency and experimental manipulation, several variable selection methods were then used to improve the evaluation of AA, and the RPD value of FT-NIRS can be increased from 3.3 to 4.1, while model of MicroNIRS became worse after variable selection due to the limited number of spectral variables and low resolution. According to the comparative analysis of the two instruments, this study could provide a useful reference and basis for instrument performance and accessible accuracy when performing rapid quality analysis of S. miltiorrhiza by NIRS.