Chemotype matters: NMR-guided profiling of Cinnamomum tamala essential oil and impact on antibacterial activity

Cinnamomum tamala (Indian bay leaf) is a widely used spice whose essential oils exhibit several pharmacological activities and the presence of several chemotypes, including eugenol, linalool, and cinnamaldehyde types. However, its quality and authenticity are frequently compromised by adulteration and compositional variability. Though comprehensive NMR-based profiling of these chemotypes remains limited, Nuclear Magnetic Resonance (NMR)-based phytometabolomics offer a robust platform for identifying and quantifying natural compounds in plant extracts including essential oils. Unlike mass spectrometry, which may not distinguish structural and configurational isomers, NMR enables precise compound characterization and quantitation even without authentic reference standards. This study aimed to apply NMR spectroscopy-based metabolomics for qualitative and quantitative profiling of C. tamala essential oils to identify chemotypic variations and to evaluate the antibacterial potential of these different chemotypes. Essential oils were extracted from C. tamala leaves collected from northern and eastern India via hydro-distillation. Quantitative ¹H NMR (qNMR) was used to determine the concentrations of major volatile compounds. Two-dimensional (2D) heteronuclear NMR and Principal Component Analysis (PCA) were employed for structural elucidation and chemotype discrimination. Sixteen volatiles were quantified, including eugenol, cinnamaldehyde, and linalool, which defined distinct chemotypes. PCA effectively differentiated oils based on metabolic fingerprints. Furthermore, minimum inhibitory concentration (MIC) of cinnamaldehyde, eugenol and linalool and their specific chemotypes were assessed using the broth microdilution method against Gram negative and Gram positive ATCC strains. Antibacterial assays revealed inhibitory potential of specific oil constituents. Taken together integration of ¹H qNMR with PCA offers a reliable approach for distinguishing regional and commercial variations and assessing safety, while antibacterial screening highlights the potential specific chemotype driven antibacterial activity and our data also suggest a cautionary note to select right chemotype of essential oils for intended applications.