Spatial mapping of metabolite distribution in Dendrobium officinale stems across different ages by MALDI-MSI

Dendrobium officinale Kimura & Migo, is a medicinal food homology plant (MFH), which has been gaining increasing attention and favor due to its nutritional and medicinal values. Sugars, alkaloids, and flavonoids are the main active substances in D. officinale and are closely related to medicinal effects. A comprehensive understanding of the spatiotemporal dynamics of metabolites' distribution is essential for optimizing harvest time and investigating biosynthetic mechanisms of D. officinale. However, the spatial distribution data on key medicinal compounds (sugars, alkaloids, flavonoids) in D. officinale from three different years stems remain limited. In this study, we employed matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to analyze metabolic profiles in three different year stems, identifying 1039 metabolites with distinct localization patterns. The analysis revealed the presence of carbohydrates (2.12 %), alkaloids (8.95 %), and flavonoids (3.46 %), displaying the highest accumulation of these bioactive compounds in three stem samples, which were more consistent with the results of physiological indicators (total alkaloids and flavonoids content). The mass spectrometry imaging further demonstrated that sugars are distributed more uniformly in D. officinale stems across different ages. Alkaloids were found to be distributed throughout the stems, with higher abundance observed in the vascular zone. Flavonoids were found to be more abundant in proximity to the stem epidermis and within the vascular bundle region. These resulting data provide a theoretical foundation for the subsequent in-depth investigation of the biosynthetic process of D. officinale metabolites.