Recent acquisitions on naturally occurring oxyprenylated secondary plant metabolites

Abstract

Oxyprenylated secondary metabolites have been regarded, for several years, merely as biosynthetic intermediates of C-prenylated compounds and only in the last decade were characterized as phytochemicals able to exert interesting and effective biological activities. Considering the length of the carbon chain attached to the oxygen atom, three types of prenyloxy skeletons can be identified: those having 5 (isopentenyl), 10 (geranyl), or 15 (farnesyl) carbon atoms. Isopentenyloxy and geranyloxy chains are quite abundant in nature, while farnesyloxy ones are by far less common. The skeleton may consist only of carbon and hydrogen or may contain oxygen atoms, usually in the form of alcohols, ethers, carboxylic acids, or ketone functionalities, and less frequently nitrogen and halogen atoms. To date, about 350 oxyprenylated derivatives were isolated from natural sources, mainly plants, fungi, and bacteria, including marine organisms, and shown to exert a variety of valuable and promising biological activities. In the last 5 years, several new phytochemical and pharmacological data about the title secondary metabolites were reported in the literature. The aim of this review is to make a survey of the most recently published data and properties of these important and interesting class of natural products, some of which have been obtained from plants that have long been used for proven or supposed medical properties, according to some ancient ethnomedical traditions.