Plants living in an environment with high bacterial density were long suspected to have protective mechanisms against infections. Due to this reason, natural products were explored initially because of their broad therapeutic values in traditional medical practice. Since these plants can be consumed by humans, the active compounds that are having therapeutic activities should be safe toward human cells. However, as science progressed, toxicological studies were performed on these active compounds to avoid their toxicity. The interest to identify and understand the biological functions and the mode of action responsible for their therapeutic roles has been escalated. To date, biologically active constituents of natural products, especially plant-derived ones, have led to the discovery of new drugs used for the treatment of numerous diseases. However, the absence of an immune system in plants, unlike humans and animals against the invaders, demanded researchers to speculate other defense mechanisms to defeat the pathogens (Koh et al. 2013), and manipulation of quorum sensing (QS) systems is considered to be a mode of defense by the plants against pathogens. © Springer India 2015.