Azadirachta indica (neem): a plant of multiple biological and pharmacological activities

Azadirachta indica, commonly called neem or ‘dogonyaro’ in Nigeria, is a plant that has found varied use in ecological, medicinal and agricultural sectors. Biological and pharmacological activities attributed to different parts and extracts of these plants include antiplasmodial, antitrypanosomal, antioxidant, anticancer, antibacterial, antiviral, larvicidal and fungicidal activities. Others include antiulcer, spermicidal, anthelminthic, antidiabetic, anti-implantation, immunomodulating, molluscicidal, nematicidal, immunocontraceptive, insecticidal, antifeedant and insect repellant effects. But toxicological activities such as allergic, genotoxic, cytogenetic and radiosensitizing effects have also been reported in humans and some economic animals, particularly, aquatic organisms, chicks and goats. Bioassay-guided studies and phytochemical analyses utilizing modern state-of-the-art techniques such as HPLC–MS, GC–MS, NMR and Infra Red spectroscopy have revealed that phytocompounds like azadirachtins, nimocinol, isomeldenin, azadirachtol (a tetranortriterpernoid), 2,3′-dehydrosalanol gedunin, nimbin, nimolicinol, odoratone, azadironolide, isoazadironolide, naheedin and mahmoodin are responsible for the varied biological, pharmacological and toxicological properties observed. In this paper, we review how a developing country like Nigeria can harness the numerous opportunities presented by the multi-biological and multi-pharmacological nature of A. indica to solve some of her myriad problems, including those in the agricultural, health and economic sectors.