Sustainable Bioactive Salts Fully Composed of Natural Products for Enhanced Pharmaceutical Applicability

Phenolic acids are attractive plant-derived bioactive substances owing to their wide range of pharmaceutical properties for the prevention of various human diseases as well as their applications in adjuvant therapy. However, phenolic acids exhibit poor water solubility, which limits their bioavailability and applications. In this study, phenolic acids were combined with matrine to form salts. Matrine is an alkaloid from a traditional Chinese herb that also has abundant pharmaceutical features and was employed to enhance the water solubility and pharmaceutical applicability of phenolic acids. Five bioactive salts, i.e., matrinium syringate, matrinium vanillate, matrinium protocatechuate, matrinium caffeinate, and matrinium gallate, were synthesized and characterized. The results show that all the salts have a hydrogen-bonding-stabilized orthorhombic crystal structure and exhibit a synergistic effect between the anions and cations. Compared with their raw materials, the salts display reduced melting points, higher water solubility (several to hundreds of times greater), lower cytotoxicity for normal human cells, as well as better anticancer, antibacterial, antioxidant, and anti-inflammatory capabilities, accompanied by relatively high thermal stability (>140 °C). This indicates that formation of salts by combining phenolic acids and matrine is an effective method for enhancing pharmaceutical applicability, which may be further used to develop new nutrients or drugs.