Medicinal plants constitute the base of health care systems in many societies. The recovery of the knowledge and practices associated with these plant resources are part of an important strategy linked to the conservation of biodiversity, discovery of new medicines, and the bettering of the quality of life of poor rural communities. Research in phytosciences, an emerging multidisciplinary science, is almost unlimited, with several aspects to be discussed. Therefore, the focus of the present review is mainly on the antimicrobial and antioxidant properties of bioactive phytocompounds resultant of our research with crude plant extracts and essential oils of medicinal plants belonging to different families, used in various infectious disorders. The results obtained in the last years warrant the present review, discussing not only the use of several medicinal plants against bacteria, yeast, filamentous fungi and protozoa, but also their mechanisms of action, interactions with macromolecules and potential for toxicity in mammalian cells. Problems related to the efficacy of the isolation techniques and stability of bioactive compounds are also commented on. In addition, this review aims to emphasize the greatest importance to investigate plant species that have not been the subject of pharmacological studies, although their popular uses have been reported.