Higher plants produce secondary metabolites involved in defense
mechanisms against herbivores, pests and pathogens. These phytochemicals have also
potential healthy properties on human organism, including antioxidant, antiinflammatory
and anti-microbial. The pressure to discover and develop new and
effective anti-infectious substances has grown due to the intensification of new and reemerging
infectious diseases as well as the increasing resistance to the antibiotics in
current clinical use. There are several approaches to control diseases caused by
microorganisms, and one of them is the use of natural bioactive chemicals that can
combat the infection. The essential oils, polyphenols and glycosidic glucosinolates
extracted from various species (e.g. medicinal and aromatic plants) have shown
promising anti-microbial activity against several pathogens responsible for human
diseases. Some of these diseases include mouth diseases as periodontitis, urinary
infections, acne, stomach cancer and ulcers associated with Helicobacter pylori, wound
infections and gastric infections. Beyond the in vitro and in vivo studies, several
compounds from the plant secondary metabolites have been subjected to clinical trials
in order to validate their efficacy as anti-infectives (e.g. proanthocyanidins, a
polyphenol, that have been tested against periodontitis or tea tree oil 4% against
methicillin-resistant Staphylococcus aureus – MRSA) for future prescription. As most
of these compounds have poor water solubility and are easily oxidized a chemical
transformation which may alter their anti-infective properties, new strategies are being considered both to protect these phytochemicals against oxidation and to enhance their
bioavailability and delivery to the desired organs. This chapter summarizes and discuss
the most promising phytochemicals that are being used to treat human diseases, antimicrobial
mechanisms, the results of clinical trials and the new approaches based on
nanoencapsulation strategies to deliver and target these compounds in vivo.
Keywords: Anti-infective properties, Bioavailability, Clinical trials, Essential
oils, Glucosinolates, In vivo anti-microbial activity, Nanoencapsulation, Phenolic
acids, Polyphenols, Proanthocyanidins.
