Structure-Based Non-targeted Mass Spectrometry Imaging Analysis of Dried Long Pepper (Piper longum)

Many studies have applied multivariate analysis to mass spectrometry imaging data to differentiate structures in a sample based on the information of compound spatial distribution. However, the actual distribution of individual compounds remains poorly documented, especially in plant samples. Here, a detailed non-targeted approach for plant sample analysis has been applied for the study of compound distribution in the medicinal species long pepper, which has a complicated internal structure. Principal component analysis discriminated between the seed and pericarp regions, resulting in peaks that were closely associated with each region. The investigation of these peaks revealed slight but potentially important distribution differences between them, despite sharing the same accumulation profile in a region. Furthermore, piperamides such as piperine and piperlonguminine are among the compounds closely associated with the pericarp region. This is the first study to report the utilization of principal component analysis for spatial feature extraction and the localization of piperamides in dried long pepper.