Understanding the mechanistic functioning of bioactive compounds in medicinal plants

Abstract

Modern synthetic medicines and antibiotics made its appearance less than 150 years ago, prior to which humans used to rely on herbal medicine for thousands of years. Plants produce secondary metabolites for their defense and signalling purposes, which exhibit a wide array of biological and pharmacological properties. These secondary metabolites conquer a large portion of currently available medicines. While diverse in their sheer number and utility, most of these bioactive compounds generally interact with few main targets in the cell like proteins, nucleic acids, and membrane. Plant phenols and flavonoids are essential sources of antioxidants like quercetin and antipyretics like aspirin. Atypical amino acids like myriocin and ranges of alkaloids like quinine, opiates, paclitaxel, and vincristine serve as plant-derived medicines. Lysergic acids used as hallucinogens and digoxin (glycoside) used in the treatment of heart failure are some other examples of important herbal drugs. Secondary metabolites like alkaloids are generally target-specific; however, others like phenolic compounds and terpene derivatives act on a wider variety of proteins through hydrophilic, hydrophobic, and ionic interactions, bringing about a change in their three-dimensional structure and imparting their bioactivity. Plant pharmaceuticals are not placebo but rational medicine with biochemically verified mode of action. The present book chapter discusses the mode of action of herbal medicines in general, along with specific biochemistry-approved mechanism for some of the important plant-derived pharmaceuticals.