Characterizing the Molecular Signatures of Plant Polyphenols with Therapeutic Potential against Calcium Oxalate Stone Pathogenesis

Abstract

The pathological crystallization of calcium oxalate monohydrate (COM) holds paramount significance within the context of human kidney stone ailment. Previous studies have suggested that polyphenols extracted from traditional Chinese medicinal herbs effectively inhibit COM crystallization, whereas the relationship between the molecular structure and their inhibitory performance remains to be elucidated. In this study, we examined a library of natural polyphenol plant extracts to investigate the influence of type, number, spatial arrangement, and length of functional groups on inhibition performance, thereby addressing a key gap in the rational design and selection of high-efficacy stone inhibitors. We combined bulk crystallization assays and microfluidic growth-kinetics measurements in aqueous solution and artificial urine with in vitro evaluations of crystal adhesion and cytotoxicity in human proximal renal tubular epithelial (HK-2) cells, as well as validation in a murine model, to systematically assess the efficacy of polyphenolic derivatives in vitro and in vivo. Our results highlight the trihydroxyl motif and ester functionalities as critical determinants of COM inhibition, consistent with preferential binding to specific crystal faces and suppression of crystal growth. Among the polyphenols, methyl gallate and ethyl gallate markedly reduced crystal–cell adhesion and crystal-induced cytotoxicity, while ethyl gallate further exhibited superior in vivo efficacy by reducing renal stone deposition, inflammation, and tubular injury. Taken together, these findings identify ethyl gallate as a promising therapeutic lead and support its further preclinical development for the management of calcium oxalate kidney stones.