Metabolomics-Based Identification of α-Glucosidase Inhibitors from Pometia pinnata Stem Bark Using LC-HRMS and...

Pometia pinnata J.R. Forst. & G. Forst. is traditionally used throughout tropical Asia and the Pacific to manage diabetes-associated hyperglycemia. However, the metabolites responsible for its α-glucosidase inhibitory activity (AGI) remain poorly characterized. This study aimed to identify putative AGI-associated metabolites from P. pinnata stem bark through metabolomics-based prioritization and tentative annotation using untargeted LC-HRMS, followed by molecular docking to assess their interactions with α-glucosidase. Thirty ethyl acetate-methanol gradient fractions were analyzed by orthogonal partial least squares (OPLS) to prioritize LC-HRMS features associated with AGI activity, followed by molecular docking of the tentatively annotated metabolites against Saccharomyces cerevisiae α-glucosidase (3A4A) and human maltase-glucoamylase (3TOP). The 75% ethyl acetate in methanol fraction showed the strongest AGI, with an IC₅₀ of 5.53 μg/mL. Five AGI-associated metabolites, namely scopoletin, 3,4-dihydroxybenzaldehyde, fisetin, 4-methoxycinnamic acid, and lindetannin, were tentatively annotated in P. pinnata stem bark based on LC-HRMS/MS data. To the best of our knowledge, these annotations have not previously been reported in P. pinnata stem bark. Among these candidates, fisetin showed the most favorable binding interactions with both target enzymes. Metabolomics-guided isolation, followed by NMR analysis, confirmed the structure of scopoletin, although the isolated compound showed weak AGI activity (IC₅₀ > 200 μg/mL). The marked difference between the parent fraction and isolated scopoletin indicates that scopoletin alone is unlikely to account for the observed activity and that other constituents may contribute. Nevertheless, this study provides a promising metabolomics-guided framework for prioritizing and tentatively annotating candidate AGI-associated metabolites in the stem bark of P. pinnata.