Organ-Specific Distribution of Antimycobacterial Neolignans in Piper rivinoides and UHPLC-HRMS/MS Analysis of Its...

This multidisciplinary study investigates Piper rivinoides, a Brazilian medicinal species, focusing on its chemical composition and antimycobacterial potential. UHPLC-HRMS/MS of leaves, stems, branches, and roots revealed 58 compounds, including neolignans, lignanamides, triterpenes, flavonoids, and carotenoids. Fourteen metabolites, notably benzofuran neolignans and pentacyclic triterpenes are annotated here for the first time. Quantitative analyses by HPLC-DAD-UV showed that eupomatenoid-5, eupomatenoid-6, and conocarpan were most abundant in leaves, reaching amounts approximately twice those found in branches and stems and about ten times higher than in roots, supporting the optimal defense theory and organ-specific accumulation of bioactive metabolites. Biological assays against Mycobacterium tuberculosis strains H37Rv and M299 revealed strong inhibitory activity for the leaf extract and isolated neolignans. Eupomatenoid-5 and eupomatenoid-6 achieved inhibition comparable to rifampicin, with low MIC₅₀ values, while conocarpan exhibited moderate activity. Antimycobacterial effects were more pronounced against the H37Rv strain, although relevant inhibition was also observed for the hypervirulent M299 strain. These findings highlight P. rivinoides as a rich source of benzofuran neolignans and promising antimycobacterial properties. The integration of advanced mass spectrometric analyses with bioassays demonstrates the value of combining chemical and biological approaches to uncover novel natural products. The putative identification of new neolignans and triterpenes, along with the confirmation of potent antimycobacterial activity, provides a robust foundation for further studies on biosynthesis, structure-activity relationships, and potential biotechnological applications.