**5. Conclusion**

This review emphasizes the importance of secondary metabolites from various sources like plants, microorganisms including bacteria, actinobacteria, and fungi and its classification, production and applications in various fields. Since there is a constant and crucial requirement for new pharmaceutical agents to fight cancers, cardiac disorders, pests, cytotoxic, mosquitoes, infectious diseases, and autoimmune disorders of both animals and plants as climate changes provide conditions favorable to repeated outbreaks of these events. The battle against any disease is a vibrant symmetry between advances in chemotherapy and natural selection on infectious or invasive agents. If the scientific community is to put constant importance in this never ending effort, then new sources of bioactive secondary metabolites with novel activities must be found. Secondary metabolites are one of their essential means of growth and defense, and these metabolites are readily available for discovery. Secondary metabolites with noteworthy biological activity are considered as an alternative to most of the synthetic drugs and other commercially valuable compounds.
