Design and Synthesis of Protocatechuic Acid Derivatives for Potential Tumoricidal Effect against Hematological Malignancies

We have investigated the tumoricidal potential of derivatives of protocatechuic acid (PCA) against tumor cells of hematological malignancies (lymphoma and myeloma). PCA (3,4-dihydroxy benzoic acid) belongs to the class of phenolic acids that naturally occur in many plant-derived foods, including olives and white grapes. PCA is a major metabolite of anthocyanin and shows strong in vitro and in vivo antioxidant activity. Novel derivatives of PCA were synthesized by adopting several different strategies, including the formation of amide derivatives, conjugation of carbohydrate moieties employing click reaction, and esterification of PCA with the inclusion of chlorine to form additional derivatives. PCA and its derivatives significantly reduced the viability and long-term growth of the myeloma cells in a dose-dependent manner. Furthermore, the PCA and its derivatives demonstrated dose-dependent tumor cell death via the significant release of lactate dehydrogenase following exposure. The PCA chloride derivative was significantly more effective compared to the other derivatives tested. PCA and its derivatives induce apoptosis of the lymphoma cells and downregulate the expression of PD-L1, suggesting its possible role in disrupting the signaling of the checkpoint pathway, thus regulating the growth of the tumor cells of hematological malignancies. Together, our data demonstrated that PCA and its novel derivatives have therapeutic applications against hematological malignancies.