Unraveling metabolic heterogeneity in black ginseng using integrated UPLC-MS and DESI-MSI with multivariate data analysis

Panax ginseng is widely utilized as a functional food ingredient. The steaming process is a critical treatment that profoundly alters the metabolic profiles and enhances the therapeutic properties of Panax ginseng . This study characterized ginsenosides, saccharides, and amino acids in eight ginseng samples using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and multivariate data analysis. A total of 224 ginsenosides were identified, with 128 compounds exclusively detected in black ginseng (BG). Quantitative analysis of 49 metabolites showed that BG was enriched in rare ginsenosides (e.g., Rg3, Rg5, and Rk1) and monosaccharides (glucose and fructose) but had lower levels of basic amino acids, particularly arginine. Partial least-squares discriminant analysis (PLS-DA) identified 10 key discriminative markers distinguishing BG from other varieties. Furthermore, desorption electrospray ionization mass spectrometry imaging (DESI-MSI) visualized the spatial distribution of these markers, revealing their preferential accumulation in the cambium and phloem tissues. These findings provide comprehensive insights into the phytochemical transformation of ginseng during mild thermal processing, facilitating the development of BG as a functional food ingredient and supporting quality control in the food industry.