Solvent-dependent metabolite profile and in vitro biological activity of frangipani (Plumeria rubra) leaf extracts.

This study aimed to investigate the influence of different solvents on the extraction of bioactive compounds and the resulting biological activities of P. rubra leaves. Extracts were obtained via maceration using methanol, ethanol, ethyl acetate, and hexane, and evaluated for total phenolic content (TPC), antioxidant activity (via DPPH radical scavenging and β-carotene bleaching), antidiabetic activity (via α-glucosidase inhibition), and antibacterial activity against Staphylococcus aureus, Salmonella typhimurium, and Escherichia coli. The extracts were also analyzed using Fourier-transform infrared (FTIR) and liquid chromatography high-resolution mass spectrometry (LC-HRMS) to identify key functional groups and metabolite profiles. Methanol extract exhibited the highest TPC (482.22 mg GAE/g) and α-glucosidase inhibitory activity (91.23%), while ethanol extract showed superior antioxidant activity. All extracts demonstrated antibacterial effects, with the methanol extract showing the strongest inhibition against S. aureus (10.71 mm). LC-HRMS revealed that hexane extract contains mostly fatty acids and triterpenoids, while the primary compound, ursolic acid, was present in methanol, ethanol, and ethyl acetate at comparable quantities. Further chemometric analysis highlighted distinct metabolite profiles and identified pheophorbide A as a primary discriminant for extract classification. Our findings suggest that P. rubra leaves, particularly when extracted with polar solvents, are a promising source of natural antioxidants, antidiabetic agents, and antimicrobials for applications in pharmaceuticals, nutraceuticals, and functional foods. In addition, the solvent-dependent phytochemical profiles can provide direction for further optimization of solvent composition for targeted metabolite extraction.

Supplementary information: The online version contains supplementary material available at 10.1007/s13205-025-04533-w.