Natural products-current and future promising source of novel drugs: A review on their antimicrobial mechanism of actions

The emergence of antibiotic-resistant pathogenic bacteria has given rise to the needs of antimicrobial compounds that derived from natural products which less likely to cause pathogen resistance. The most profound and traditional example of the antimicrobial from the nature is antimicrobial peptides (AMPs) that serve as natural innate barriers limiting microbial infection or act as an integral component in response to inflammation or microbial infection. Cytoplasmic membrane, appeared as the first targeting action of these peptides pertaining to the amphipathicity and cationic-charged of the compounds in nature, which allow them to attach, translocate and eventually inserted into the inner region of the microbial cells. In fact, many studies have proven that some of the AMPs can even adopt more than one mechanism in inhibiting the microbial cells. This chapter aims to review and explain in depth the antimicrobial mechanism of actions of natural proteinaceous and non-proteinaceous compounds from various plant and animal sources. Preparation/extraction, treatment and purification of the extracted antimicrobial compounds will also be discussed.