Recent Trends and Perspectives for the Extraction of Natural Products
In this chapter we present and discuss the most recent trends and perspectives on the extraction of natural products. This was made considering: (i) the natural‐origin extracts/target compounds that are currently being more studied and extracted (as well as in their potential applications); (ii) the most recently extracted vegetable raw materials that can be explored as sources for the envisaged target compounds; (iii) the current and most promising strategies regarding the extraction methodologies that are expected to be further developed and employed on the extraction of natural products; and (iv) the novel/alternative solvents, solvent mixtures and extraction additives that could be beneficially used in the above referred extraction methodologies. To accomplish this task, we performed a literature search (covering the period between 2000 and 2011) and used several specific search descriptors in order to verify the above referred trends in the extraction of natural products. Results showed that, in recent years, there has been a clear renewed/increased interest in the extraction of natural products and in their advantageous applications, namely as food supplements, phytomedicines, nutraceuticals, cosmetics and natural pesticides. The most used natural‐origin raw materials to obtain these natural products were terrestrial plant‐origin raw materials. In addition, there was a greater interest in the extraction from plant residues/wastes, from marine organisms and from microorganisms. In terms of the most employed natural products extraction methods, supercritical fluid extraction methods seemed to keep the interest of researchers, while other methods, such as ultrasound, microwave, pressurized‐liquid, sorptive and combined/hyphenated extraction techniques, have gained more attention in recent years. Finally, a recent interest was also observed in using novel extraction solvents (or solvent mixtures) that may improve process safety and sustainability, and/or that may improve extraction yields, selectivities and stabilities of the target compounds. Moreover, it is expected that the observed trends will be maintained in the near future as they were mostly motivated by recent consumer demands and by safety, environmental and regulatory issues.