Comprehensive Multiscale Characterization, in vivo Antioxidant Activity, and Subacute Toxicity Assessment of Pearl Powder.

Ethnopharmacological relevance Pearl powder has been used for centuries in Traditional Chinese Medicine for its detoxifying, regenerative, and anti-aging properties. This study evaluates the antioxidant efficacy and safety of pearl powder derived from Hong Kong pearl oysters ( Pinctada imbricata ). Aim of the study The present study aimed to perform a comprehensive multiscale physicochemical characterization of pearl powder and to investigate it’s in vivo antioxidant activity and subacute oral toxicity in C57BL/6J mice. Materials and methods The powder was characterized using Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM), atomic force microscopy (AFM), BET surface area analysis, and X-ray photoelectron spectroscopy (XPS). In vivo antioxidant activity was assessed in male C57BL/6J mice (n = 12 per group) administered pearl powder orally at 250, 500, and 1000 mg/kg body weight daily for 4 weeks using FRAP, TEAC, ORAC, and MDA assays. A 28-day subacute toxicity study was conducted according to OECD Guideline 407 (500–1000 mg/kg b.w., n=5/sex/group). Results Dose-dependent increases in FRAP, TEAC, and ORAC, together with reduced MDA levels, were observed especially in liver, kidney, and spleen (p < 0.05 to p < 0.0001). The toxicity study showed no mortality, clinical signs, or histopathological changes. Minor non-adverse biochemical variations lacked supporting pathology, establishing a No Observed Adverse Effect Level (NOAEL) of 500 mg/kg b.w. Conclusion These findings demonstrate pearl powder’s potent antioxidant activity with a favorable safety profile, supporting its development as a natural therapeutic agent for oxidative stress-related conditions. Nonetheless, confirmation through clinical studies will be important to substantiate these preclinical observations.