Synergy-driven anti-inflammatory, analgesic, and antipyretic effects of HPLC-standardized Cassia tora extract and nanochitosan: Chou-Talalay CI/DRI and IL-6/PGE₂ mechanism

Inflammation is a major pathological process underlying pain and fever, and plant-derived agents may provide multitarget therapeutic benefits, although their use is often limited by poor dose efficiency and variability in phytochemical composition. This study aimed to standardize an ethanolic seed extract of Cassia tora and determine whether formulation as extract-loaded nanochitosan could enhance its anti-inflammatory, analgesic, and antipyretic activities compared with the free extract, blank nanochitosan, and a non-associated physical mixture at equivalent extract doses. The extract was standardized by high-performance liquid chromatography fingerprinting and marker quantification, followed by formulation into nanochitosan. In male Swiss mice (n = 6–10/group), in vivo synergy was evaluated on serum interleukin-6 in carrageenan-induced paw inflammation using Chou-Talalay analysis, with further assessment of paw edema, nociception, yeast-induced pyrexia, and serum prostaglandin E₂. Extract-loaded nanochitosan formed stable monodisperse nanoparticles with high encapsulation efficiency, sustained 24 h release, and better storage stability than the physical mixture, which showed aggregation and sedimentation. The formulation produced the greatest dose-sparing synergy and significantly improved edema, pain, and fever outcomes, accompanied by suppression of interleukin-6 and prostaglandin E₂. These findings indicate that nanochitosan loading enhanced the pharmacological activity of standardized Cassia tora extract, possibly through modulation of the interleukin-6–prostaglandin E₂ pathway.