Process-Induced Modifications in Total Soluble Matter, Antioxidant Activity, Metabolomic Profile, and Microstructure of Turmeric (Curcuma longa L.) Extracts Under Ultrasound-Assisted Ethanol Extraction.

This study investigated the effects of ultrasound-assisted extraction (UAE), ethanol concentration (0%, 20%, 50%, 80%, and 99.5%), temperature (30°C, 50°C, and 70°C), and time on turmeric extraction by analyzing total soluble matter (TSM), antioxidant activity, and metabolomic profiles using ultra-performance liquid chromatography (UPLC)-QTOF-MS and multivariate analysis. TSM generally increased with temperature and ethanol concentration, reaching its highest value at 50% ethanol and 70°C (20.44 g/100 g); under these conditions, TSM plateaued by 60 min and remained stable up to 200 min. Four-way analysis of variance (ANOVA) confirmed significant condition-dependent effects on TSM, whereas the UAE-CE (conventional extraction) differences in antioxidant activity were primarily associated with ethanol concentration (p < 0.001). UAE generally produced higher TSM and antioxidant activities than CE, with the greatest improvement observed at 30°C and intermediate ethanol concentrations (50%-80%). Representative scanning electron microscopy and quantitative image analysis demonstrated that extensive structural disruption with 99.5% ethanol caused severe surface opening but did not achieve the highest TSM, whereas UAE with 80% ethanol induced moderate tissue permeabilization and more complex boundary morphology, yielding superior extraction performance. Heatmap and principal component analysis (PCA) analyses revealed solvent- and method-dependent variation in metabolite profiles. Qualitatively, UAE at 30°C recovered a comprehensive curcuminoid and lipid profile comparable to CE at the same temperature. Following rigorous false discovery rate (FDR) correction, statistically significant differences were restricted to a limited compound subset, demonstrating that UAE maintains overall metabolic integrity under mild thermal conditions. Ultimately, these findings support the potential of low-temperature UAE parameters for efficient recovery of functional turmeric bioactives.