Study of plant species with antimicrobial activity

This doctoral thesis investigates the antibacterial and antiviral activities of plant extracts and agro-industrial by-products. The study is divided into two main sections. The first part involved the phytochemical analysis of plant extracts, with the isolation and identification of metabolites through chromatographic techniques (flash chromatography, RP-HPLC) and structural elucidation (NMR, ESI-MS). A total of nine compounds, including two new diterpenes, were isolated from the exudate of Commicarpus grandiflorus (A. Rich.) Standl. (Nyctaginaceae); among them, commicarpotriol showed activity against Streptococcus mutans. Zanthoxylum rhoifolium Lam. (Rutaceae) extracts yielded twenty-nine metabolites, including three new sesquiterpenes and a novel α-ionone, although the extracts did not show significant antibacterial activity. In contrast, Euphorbia paganorum A. Chev. (Euphorbiaceae) extracts yielded eleven diterpenes, including five novel. At 500 μg/mL, the n-hexane and chloroform extracts reduced the viability of Bacillus clausii, Shigella dysenteriae, S. mutans, Listeria monocytogenes, and Enterococcus faecalis. The second section applies Orbitrap-based metabolomic analysis. A supercritical CO₂ soybean (Glycine max (L.) Merr.) extract, rich in N-acylethanolamines, proved virucidal against Zika virus. Grape pomace (Vitis vinifera L.) extract inhibited Influenza A and HSV-2 at 3 mg/mL. Finally, Baharat spice blends showed synergistic antimicrobial effects, with trace metal levels within WHO/FAO limits. Overall, this thesis highlights the value of phytochemical and metabolomic analyses in identifying novel bioactive compounds.