The importance of natural products in the pharmaceuticalindustrycannot be abated because it playsvital role in the prevention and treatments of diseasessuch as cancer, malaria, pile etc. These natural products which include alkaloid, flavonoid, phenol, saponin and tannin are bioactive compounds in plant and essential in plant metabolic activities. All of these have been tested for their huge medicinal properties and therefore could serve as an alternative medicine in treatment of myriad ailments. Although, through the modern-day technologies, these bioactive compounds have been separated from the plants and synthesized into capsules and tablets for easy administration, usage and storage, there is a need to create awareness on the side-effects associated with excess or abuse of medicinal plants and to encourage rational use of natural resources for sustainability. Thus, this review gives an overview on pharmacological importance of named alkaloids, methods of extraction and purification of alkaloids in plant, laying emphasis on side-effects associated to the abuse of alkaloids or alkaloid derivative drugs.