Chemistry Proceedings

Natural products are an important source of chemically diverse metabolites with potential antimicrobial applications. Origanum vulgare L. is an aromatic and medicinal species known to contain phenolic compounds, flavonoids, and terpenoids associated with antibacterial activity. This study evaluated the influence of sequential extraction with solvents of increasing polarity (n-hexane, ethyl acetate, and methanol) on the antibacterial activity of O. vulgare leaf extracts against Escherichia coli and Staphylococcus aureus using the agar disk-diffusion method. Extracts were tested at 25, 50, 100, and 200 µg/mL. None of the extracts inhibited E. coli. In contrast, the ethyl acetate and methanol extracts inhibited S. aureus, with inhibition zones ranging from 7mm to 1.1 mm and from 9 to 12 mm, respectively; the n-hexane extract was inactive. The methanol extract produced the largest inhibition zone (12 mm at 200 µg/mL). These results indicate that antibacterial activity varied with both solvent polarity and bacterial species and support further phytochemical characterization of the active extracts to identify the metabolites associated with the observed activity.

Phyla dulcis (Trevir.) Moldenke, commonly known as “hierba dulce”, is a medicinal plant traditionally used in Mexican ethnomedicine to treat various ailments. However, its antimicrobial potential and chemical constituents remain insufficiently explored. In this study, the antimicrobial activity of hexane, ethyl acetate, and methanolic extracts of P. dulcis was evaluated against Staphylococcus aureus using the agar diffusion method. Extracts were tested at concentrations ranging from 12.5 to 200 μg/μL, and the inhibition zones were compared with those produced by standard antibiotics used as positive controls. The extracts showed concentration-dependent inhibitory effects, with the ethyl acetate and methanolic extracts displaying the most promising activity. The observed antimicrobial response suggests that semipolar and polar fractions may contain bioactive secondary metabolites responsible for the inhibitory effects against S. aureus. These findings support the potential of P. dulcis as a source of antimicrobial compounds and encourage further phytochemical studies aimed at isolating and characterizing its active constituents.

Multicomponent reactions (MCRs) lead to products in a single step starting from three or more components with high atom efficiency and conversion. They are used in medicinal chemistry and drug discovery usually for small-molecule library generation and structure–activity relationship investigations. However, recently, as covalent protein labeling became more and more popular, the application of MCRs in chemical biology and at protein labeling emerged as a new approach. The small-molecule reactants form a covalent bond with a specific amino acid side chain of the target protein that is in most cases Lys or N-terminus and in a few occasions Asp or Glu. We report the first steps towards multicomponent protein labeling via systematic investigation of MCRs in those Lys, which could be one of the reactants.