This study investigated the astringency of Camellia ptilophylla green tea, using Yunnan large-leaf green tea as a control. Sensory evaluation and turbidity and fluorescence quenching methods based on artificial saliva were combined to compare the astringency intensities of the two teas. High performance liquid chromatography (HPLC) was employed to analyze changes in the concentration of the major polyphenols after artificial saliva treatment identifying the major astringent polyphenol monomers. The interactions between these polyphenols and a salivary protein model were further explored using fluorescence spectroscopy and molecular docking. Non-targeted metabolomics based on high-resolution mass spectrometry was used to identify other astringent polyphenols. The results showed that C. ptilophylla green tea exhibited stronger astringency than did Yunnan large-leaf tea, with gallocatechin gallate, 1,2,4,6-tetragalloyl glucose, and gallocatechin-3,5-digallate identified as the major astringent polyphenols. These polyphenols interacted with the salivary protein model predominantly through hydrophobic interactions and hydrogen bonding. Additionally, myricetin, emodin and taxifolin also showed high binding affinity to the salivary protein model. This study provides insights into the chemical basis for the astringency of C. ptilophylla green tea and lays the groundwork for further research into the mechanism underlying its astringency and for exploring strategies to improve its flavor.

To reveal the chemical composition profile of Camellia ptilophylla, a rare natural low-caffeine tea variety, nontargeted metabolomics based on high-resolution mass spectrometry (HR-MS) was employed to identify the metabolite composition of green tea and black tea from C. ptilophylla and C. sinensis var. assamica. Additionally, the metabolomic differences between the two types of tea and between the two tea varieties were analyzed using principal component analysis (PCA), cluster analysis (CA), and orthogonal partial least squares-discriminant analysis (OPLS-DA). Differential metabolites were identified using standards and database. A total of 152 metabolites were identified in the four tea samples, the major ones being flavonoids (42%). These metabolites were categorized into four clusters. The metabolomic difference between C. ptilophylla and C. sinensis var. assamica was more pronounced than that between green and black teas. Notably, 24 metabolites including theasinensin B isomers, theobromine and 14 flavonoids such as tetrahydroxyxanthone and epitheaflagallin 3-O-gallate, which were more abundant in C. ptilophylla green tea than in C. sinensis green tea, were considered as the characteristic metabolites of C. ptilophylla green tea. In black tea from C. ptilophylla, 40 characteristic metabolites were identified including 25 flavonoids such as gallocatechin-3,5-digallate, tetrahydroxyxanthone and dihydromyricetin; 4 tannins such as theaflavin 3-gallate, theasinensin A isomers and theaflavin 3,3’-digallate; and theobromine. This study provides a reference for further exploration of bioactive compounds in C. ptilophylla.