Page - (000235) - in Biomedical Chemistry: Current Trends and Developments

3.1.3 Peptides for Biomedicine To fulfil their therapeutic function, most drug-like compounds must pass through the cellular membrane to enter a cell. Small molecules that obey Lipinski’s rule of five (no more than 5 hydrogen bond donors, not more than 10 hydrogen bond acceptors, a molecular mass less than 500 Da and an octanol-water partition coefficient not greater than 5) have a reasonable chance of penetrating the cell membrane. However, an increasing number of therapeutics, such as biologics, cannot be considered ‘small molecules’ and these therapeutic are often unable to enter the cell unassisted (Liskamp, 2014). One of the vehicles used to facilitate the passage of these compounds into cells are peptides. Peptides and proteins play a central role in numerous biological and physiological processes in living organisms: they are involved as hormones and neurotransmitters in intercellular communication, act as antibodies in the immune system to protect organisms against foreign invaders, and are also involved in the transport of various substances through biological membranes. Peptides have significant advantages over other small molecules in terms of specificity/affinity for targets and toxicity profiles, and over antibodies in terms of tissue penetration owing to their smaller size. A large number of peptide-based drugs are now being marketed and the number of candidates entering clinical evaluation in recent years is steadily increasing. Therefore, the synthesis of such structures has been a major focus of organic chemistry for over a century in order to improve the prospects for synthetic therapeutic peptides. In this section, the relevance of peptides in biomedicine will be discussed. 3.1.3.1 Antimicrobial Peptides (AMPs) Parasitic diseases are most common in tropical regions with poverty and undeveloped health care systems. Many parasitic diseases have been out of focus on national and international agendas and increasing drug resistance combined a lack of vaccines in several countries make this very alarming. To combat this reality, it is imperative to understand the relationship between insect and host associated to parasitic disease.