In-situ detection and imaging of Areca catechu fruit alkaloids by MALDI-MSI

Arecoline, the predominant alkaloid in the fruit of Areca catechu, is considered the fourth most consumed addictive drug in the world, after nicotine, alcohol, and caffeine. Additionally, the areca nut (AN) is widely used in traditional and herbal medicines. Therefore, performing an exact analysis of alkaloids will provide evidence for more optimal applications of AN. Here, we performed matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) and image 10 physiologically active alkaloids in situ (arecoline, arecaidine, caffeine, cotinine, guvacine, guvacoline, hordenine, sophoridine, trigonelline, and vicine) in areca fruits at three different developmental stages. The ion images obtained by MALDI-MSI describe in detail the spatial distributions in different tissues of the fresh fruit of A. catechu, i.e., exocarp, mesocarp, endocarp, episperm, endosperm, and embryos. Liquid chromatography coupled with tandem MS (LC-MS/MS) was also carried out to verify the relative abundance and confirm the quantitative distribution of these alkaloids in Pericarpium Arecae and Semen Arecae. In this study, 3,4-dimethoxycinnamic acid (DMCA) was evaluated as a new matrix for enhanced low-MW compound detection by MALDI-MSI in A. catechu fruit for the first time. New insights into the physiological activities and pharmaceutical properties of areca fruits for further applications can be obtained.