Spatial metabolomics reveals the spatiotemporal dynamics of sugars and anthocyanins during Lycium ruthenicum fruit ripening

ABSTRACT Lycium ruthenicum Murr. is a notable botanical resource that has been shown to possess substantial antioxidant activity. The primary antioxidant compounds present in the substance under investigation are carbohydrates and anthocyanins. In order to investigate the dynamics of these metabolites during fruit development, berries were categorised into three stages: young fruit (LR1), colour transition (LR2), and mature fruit (LR3). A thorough investigation has been conducted, which has revealed a significant accumulation of bioactive compounds and an enhancement in functionality. In fruits LR3, the levels of total polysaccharides, total anthocyanins, and antioxidant activity reached 1.61-fold, 3.5-fold, and 1.75-fold those of the fruits LR1, respectively. The spatial distribution of metabolites within fruit tissues is critical for enhancing postharvest quality, yet this aspect remains unexplored in L. ruthenicum . In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging (MALDI-MSI) was employed to analyse metabolic profiles at three stages of fruit development. In the course of the analysis, 638 metabolite-related features were putatively annotated; of these, 6.6% were carbohydrates, 9.2% were polyketides, and 19.7% were shikimate and phenylpropanoids, including four putatively annotated anthocyanin components. The application of mass spectrometry imaging in conjunction with untargeted metabolomics has revealed that monosaccharides primarily accumulate in the pulp and peel, exerting a direct influence on flavour. The transition of anthocyanins (e.g. pelargonidin-3-glucoside) from a concentrated epidermal distribution to a homogeneous distribution was observed as the content increased, reaching a peak in fruit LR3. This pattern is closely associated with postharvest color uniformity. It is noteworthy that the overlapping spatial distribution of specific sugars and anthocyanins implies a potential association in antioxidant defense. On this basis, we propose the hypothesis that sugar supply promotes the glycosylation and accumulation of anthocyanins. These findings deepen the understanding of metabolite distribution in L. ruthenicum and provide a new direction for spatial regulation of fruit quality.