Unveiling spatial distribution of flavonoids and polysaccharides in four-year-old Polygonatum cyrtonema Hua rhizome via MALDI-MSI

Polygonatum cyrtonema Hua has been attracting attention of Asian countries as a traditional herbal medicine. Unveiling the spatial distribution accumulation of key metabolites is of great worth for investigating its nutritional and medicinal values. However, their spatial distribution information during different growth period (four-year-old) in rhizome has not been extensively explored, due to the lack of efficient analytical techniques. In this study, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is employed to visualize the spatial distribution of metabolites in different growth period rhizome sample (Y1, Y2, Y3, Y4). From the mass spectrum imaging, the flavonoids (chalcone, Artemetin, Peganetin, Kaempferol and Icariin) and carbohydrates (Cellobiose, 1-Kestose, Sucrose acetate isobutyrate, D-Galactose, α, β-Trehalose, Raffinose, β-Cyclodextrin were distributed evenly throughout the entire rhizome. Additionally, several flavonoids were down regulated with (27.03 %) in Y2 sample, which indicated that they apparently played protective roles in growth development in response to abiotic and biotic stress. From the collected molecular imaging data, flavonoids were observed toward the edges of rhizome and up-regulated in response to high UV radiation, indicating ability of protection against oxidative stress. Contrarily, polysaccharides dispersed increasing visualization per growth period. Comparative analysis indicated metabolites abundance thoroughly in Y4 sample, due to adopting defense against environmental stress. This study reveals an overview of the spatial distribution and accumulation of key metabolites in four-year-old P. cyrtonema rhizome, that highlight their significant roles in physiological processes as well as their potential medicinal value. Using MALDI-MSI, we characterize differential expression of flavonoids and carbohydrates. The results shows adaptive responses to environmental stress, that revealing new aspects to the nutritional and therapeutic properties.