Naturally occurring prenylated flavonoids from African Erythrina plant species

Flavonoids refer to a large class of secondary metabolites with a unique skeleton comprising two aromatic rings linked together by a C₃ unit. This class of compounds is largely distributed in plants and rarely occurs in fungi. Some of these compounds are directly bonded to prenyl units. Prenyl groups are C-5 carbon units derived from the mevalonate pathway, are reported to substantially improve the biological activities of diverse classes of secondary metabolites. Prenylated flavonoids display a broad spectrum of biological activities, including antibacterial, antioxidant, anticancer, antidiabetic and antiviral activities. Some flavonoids have already been formulated as either medicines or dietary supplements and are currently used in the management of certain medical conditions. The continuous search for bioactive molecules is a global concern; and encapsulating the contribution of each continent and/or country in terms of available resources should be a priority. This paper aims to methodically summarize the bioactive prenylated flavonoids characterized from plants of the genus Erythrina growing in Africa, as well as their distribution in the genus. Approximately 289 prenylated flavonoids have been isolated and characterized exclusively from plants belonging to the genus Erythrina growing in Africa, covering all the subclasses of flavonoids bearing prenyl group(s), namely, flavanones, flavones, chalcones, isoflavanones, isoflavones, isoflavans, isoflav-3-enes, pterocarpans and pterocarpenes isolated from 1981 to date. This review encompasses the data gathered from 202 peer-reviewed articles and covers the source, isolation, distribution of Erythrina plant species throughout the continent, structure elucidation of prenyl moieties, biological activities as well as the in silico tests where available towards some targets in drug discovery.