Variations in morphology, physiology, and multiple bioactive constituents of Lonicerae Japonicae Flos under salt stress

Lonicerae Japonicae Flos (LJF) is an important traditional Chinese medicine for the treatment of various ailments and plays a vital role in improving global human health. However, as unable to escape from adversity, the quality of sessile organisms is dramatically affected by salt stress. To systematically explore the quality formation of LJF in morphology, physiology, and bioactive constituents' response to multiple levels of salt stress, UFLC-QTRAP-MS/MS and multivariate statistical analysis were performed. Lonicera japonica Thunb. was planted in pots and placed in the field, then harvested after 35 days under salt stress. Indexes of growth, photosynthetic pigments, osmolytes, lipid peroxidation, and antioxidant enzymes were identified to evaluate the salt tolerance in LJF under different salt stresses (0, 100, 200, and 300 mM NaCl). Then, the total accumulation and dynamic variation of 47 bioactive constituents were quantitated. Finally, Partial least squares discrimination analysis and gray relational analysis were performed to systematically cluster, distinguish, and evaluate the samples, respectively. The results showed that 100 mM NaCl induced growth, photosynthetic, antioxidant activities, osmolytes, lipid peroxidation, and multiple bioactive constituents in LJF, which possessed the best quality. Additionally, a positive correlation was found between the accumulation of phenolic acids with antioxidant enzyme activity under salt stress, further confirming that phenolic acids could reduce oxidative damage. This study provides insight into the quality formation and valuable information to improve the LJF medicinal value under salt stress.