A useful quantitative model for determining the optical purity of praziquantel enantiomers based on near infrared spectroscopy with partial least squares

In this study, a new method was developed for the determination of praziquantel (PZQ) enantiomers in solution. Praziquantel, as a highly effective and low-toxic broad-spectrum antiparasitic drug developed in the 1970s, is the first choice for the etiology of schistosomiasis treatment recommended by the World Health Organization. It is by far the most effective anti-schistosomiasis drug. PZQ is a chiral drug with a chiral carbon atom and two enantiomers, of which R-PZQ is the main contributor of the anti-schistosome effect. The quantitative model was established based on near infrared (NIR) spectroscopy combined with the partial least square (PLS) method. Using sucrose as a chiral selector, the collected spectral information was processed by the second derivative and Savitzky-Golay smoothing filter, and comprehensively analyzed in the two bands of 1816.9–1884.3 nm and 1405.3–1425.4 nm to establish a good PLS regression model. Internal cross-validation of the model was carried out. In principle, the enantiomeric excess could be determined as low as 1.33%. The mole fraction of S-PZQ determined by HPLC was used as a reference method, and three batches of samples from the same manufacturer were used for independent external validation with an error of ± 4%. The results showed that this quantitative model could be used to determine the enantiomer content of the chiral drug PZQ. It realized the rapid and sensitive analysis of PZQ tablets and provided a new strategy for the quality analysis of chiral drugs.