Research advances for the extraction, analysis and uses of anthraquinones: A review

Abstract A current economic trend is to highlight natural resources, and many plant species are rich sources of anthraquinones. The latter are natural compounds that have various biological properties with subsequent positive and/or negative effects, and have found industrial application as natural dyes. The potential of anthraquinones to inhibit or prevent fungal and bacterial growth are two interesting biological properties, but many other properties are attributed to them, such as antioxidant, anticancer, anti-inflammatory, laxative and many others. Each biological property attributed to anthraquinone derivatives is listed with several research works. These last ones are described in terms of materials and results. The intensity of research focused on natural compounds valuation from natural and suitable substances has been growing over the past few decades. In term of publications, anthraquinones have been the most studied in China with around 1/2 of publications (44%). The article mainly provides a handy overall of different extraction methods, analysis techniques, whereas bioactive properties and industrial applications from various plant species containing anthraquinone derivatives are also reported. Numerous extraction and analysis methods are reviewed: Ultrasonic assisted, microwave, pressurisated fluid and supercritical fluid extraction, for the first, capillary electrophoresis, thin layer, liquid, gaseous, countercurrent and supercritical fluid chromatography for the second. Each technique is fundamentally explained and several studies dedicated to anthraquinones have been explored, describing both the part of the studied plant in which are located the anthraquinones (roots, leaves, seeds, flowers) and the physico-chemical properties of these compound (volatility, acidity). The influence of parameters to optimize extraction and analysis methods are carefully described, and advantages of modern approaches are reported with regards to traditional ones, in terms of time and solvent consuming and efficiency. Finally, the most of the studied plants containing anthraquinone derivatives were from mainly 3 families (81%): Polygonaceae , Rubiaceae and Fabaceae . The best known as anthraquinones are: rhein, aloe emodin, emodin, physcion, chrysophanol that are described in most studies and given as responsible of several biological properties. For industrial applications, these compounds are used as natural dyes to replace synthetic chemicals in formulation in order to prevent some side effects.