The recent changes in demographic trends of society as well as the emergence of new research amalgamations of nutritional and pharmaceutical sciences have provided great opportunities for the utilisation of plant food products. There is currently significant interest in the nutraceutical industry, and the search for new health-exhibiting and somewhat toxicity-inducing naturally occurring plant compounds is on the rise. Bioactive components in plants are essentially secondary metabolites that can display pharmacological or toxicological response in humans and animals alike. These metabolites are produced concomitantly with the primary biosynthetic compounds that are responsible for plant growth, development, signalling and protection, and once ingested can produce beneficial health effects on many levels. Furthermore, the beneficial health properties of bioactive compounds are primarily due to their possession of exceptional antioxidant properties when applied in relatively small amounts. This unique feature extends to the majority of their conjugate metabolites to a similar extent as observed in their pure forms. Most of the plant species are capable of producing these compounds from relatively small levels to exceptionally high concentrations however, the variety of externally controlled factors are also influential for the levels found in plants themselves. The aim of this chapter is to provide an introduction to key plant bioactive compounds classification, description of some most important plant bioactive compounds as well as putative mechanisms of action that these bioactive compounds possess and their significance in the use in today's nutraceutical industry.