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.