Indole (C8H7N) is a weakly basic molecule consisting of a pyrrole ring fused to a benzene nucleus, and ten π electrons move throughout the structure. The basic environment of indole alkaloids is thought to be caused by the delocalization of the lone pair of nitrogen electrons into the free circulation of the π electronic system. This results in indole becoming protonated at the C-3 position, which is thermodynamically more stable.Indole alkaloids have gained popularity due to their diverse pharmacological activities. Indole alkaloids have been identified in several prominent plant families, including Apocynaceae, Rubiaceae, Nyssaceae, and Loganiaceae, among others. Some of the identified indole alkaloid compounds have been highly effective in pre-clinical and clinical studies. Thousands of compounds containing the indole nucleus have been isolated from plant sources. Their pharmacological activities were assessed, with some now being examined in clinical trials and some already approved for therapeutic use in humans. Indole alkaloids are often characterized by their potent biological activities, which are relevant to the field of medicine, including anticancer, antibacterial, antiviral, antimalarial, antifungal, anti-inflammatory, antidepressant, analgesic, hypotensive, anticholinesterase, antiplatelet, antidiarrheal, spasmolytic, antileishmanial, lipid-lowering, antimycobacterial, and antidiabetic activities.