Natural Antimicrobials from Plants Used as Food Preservatives

Plant-derived antimicrobial compounds are emerging as promising alternatives to synthetic preservatives in the food industry due to their efficacy against a broad spectrum of pathogenic and spoilage microorganisms, as well as their consumer acceptance. This review critically examines the main classes of bioactive phytochemicals, including essential oils, polyphenols, alkaloids, terpenoids, and saponins, comparing their relative antimicrobial effectiveness and highlighting representative examples. Notably, essential oils rich in thymol or carvacrol have shown strong inhibitory activity against Listeria monocytogenes and Salmonella spp., while polyphenols and alkaloids exhibit moderate to strong activity depending on concentration and food matrix. Their mechanisms of action include cell membrane disruption, inhibition of key enzymes, and interference with DNA or protein synthesis. Applications in food systems (i.e., incorporation into coatings, emulsions, or controlled-release formulations) demonstrate potential for extending shelf life and enhancing safety. However, practical implementation is challenged by matrix-dependent efficacy, compound stability, sensory impact, and regulatory and toxicological considerations. By synthesizing current knowledge, identifying the most promising compound classes, and highlighting key limitations, this review provides a critical framework to guide future research and the development of effective, sustainable natural preservatives in the food industry.