**5. Conclusions**

Cyanidin was the most abundant anthocyanidin in purple leaf Chinese cabbage, with an average content of 5741.20 mg/kg, accounting for 95.7% of the total anthocyanidins. The prediction models established using visible/NIR spectroscopy on the basis of PLSR after no scattering processing and first-order derivative pretreatment method were suitable and effective for accurate and fast quantification of cyanidin and total anthocyanidin contents in PCC. The result laid a foundation for the application of NIR, with its obvious timesaving, convenience, and organic solvents free advantages, in the fast prediction of anthocyanidins in vegetables and rapid screening of purple vegetable breeding materials.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/foods12091922/s1, Table S1: Contents of anthocyanidins in purple Chinese cabbage analyzed by high-performance liquid chromatography (mg/kg).

**Author Contributions:** Conceptualization, D.-S.Z. and H.-J.H.; software, G.-M.L.; validation, Y.-Q.W. and L.-P.H.; formal analysis, G.-M.L. and X.-Z.Z.; investigation, Y.-Q.W. and X.-Z.Z.; data curation, G.-M.L. and L.-P.H.; writing—original draft preparation, Y.-Q.W.; writing—review and editing, Y.-Q.W., L.-P.H. and H.-J.H.; supervision, D.-S.Z. and H.-J.H.; project administration, H.-J.H.; funding acquisition, D.-S.Z. and H.-J.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Key Research and Development Program of China (No. 2022YFD1200805), Innovation and Capacity Building Project of Beijing Academy of Agriculture and Forestry Sciences (KJCX20200213, KJCX 20210437), National Natural Science Foundation of China (No. 31872094), and Beijing Innovation Consortium of Agriculture Research System (BAIC01-2022).

**Data Availability Statement:** Data is contained within the article or supplementary material.

**Conflicts of Interest:** The authors declare no conflict of interest.
