Xanthones are one of the biggest classes of compounds in natural product chemistry. A number of xanthones have been isolated from natural sources of higher plants, fungi, ferns, and lichens. They have gradually risen to great importance because of their medicinal properties. This review focuses on the types, isolation, characterization, biological applications, and biosynthesis of naturally occurring xanthones isolated so far. Different physicochemical and instrumental methods such as liquid-solid and liquid-liquid extraction, TLC, flash chromatography, column chromatography, IR, 1H NMR and 13C NMR spectroscopy, GLC, HPLC, GC, and LCMS have been widely used for isolation and structural elucidation of xanthones. Hepatoprotective, anticarcinogenic, antileprosy, antimalarial, antioxidant, anticholinergic, mutagenicity, radioprotective, immunomodulatory, antibone resorption, antiparasitic, neuraminidase inhibitory, anticomplement, antibacterial, antifungal, algicidal, anti-HIV, cardioprotective, antitumoral, antidiabetes, antihyperlipidemic, antiatherogenic, anti-inflammatory, antiulcer, antidiabetic, hypolipidemic, analgesic, antiasthmatic, antihistaminic, antiamoebic, diuretic, antidiarrheal, larvicidal, and ovicidal activities have been reported for natural occurring xanthones. To a certain extent, this review provides necessary foundation for further research and development of new medicines.

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Naturally Occurring Xanthones: Chemistry and Biology

The family Gentianaceae includes about 1700 species over 90 genera. These plants are known to biosynthesise, in particular, rare polyphenolic pigments known as xanthones. They also produce flavonoids, as well as monoterpene glycosides (secoiridoids) which are their bitter principles. Numerous phytochemical studies have involved these constituents due to their pharmacological and chemotaxonomic relevance. The strategies used for the isolation of the different constituents of the Gentianaceae as well as their chemical characterisation are discussed, and different analytical methods (LC-MS, LC-UV-PDA and LC-NMR) used for the profiling of these constituents in different species of the Gentianaceae are presented. Examples are also given how these approaches are used to establish chemotaxonomic relationships between species with discussion on chemotaxonomic aspects mainly focused on two subtribes, the Gentianinae and Swertiinae.

Profiling, Isolation, Chemical Characterisation and Distribution of Gentianaceae Constituents

Gentianaceae have a long history of use as traditional remedies for the treatment of various ailments. The medicinal properties of crude herbal drug are attributed to bitter glycosides, flavonoids, and xanthones, the main plant secondary metabolites. These plant-derived molecules, especially naturally occurring xanthones, possess a broad spectrum of bioactivity, being anticarcinogenic, antimicrobial, neuroprotective, antidiabetic, and cardioprotective. Most Gentianaceae species are rare and endangered by uncontrolled overharvesting and influences of various environmental factors (habitat loss, climate change, and invasive species spreading). The decline of Gentianaceae species poses a high risk to the loss of an enormous diversity of potentially bioactive compounds. In this chapter we will summarize the pharmacological activities of identified secondary metabolites from endangered species belonging to four Gentianaceae genera (Gentiana, Gentianella, Centaurium, and Swertia), as well as the importance of biodiversity conservation in the context of their biotherapeutic potential.

Secondary metabolites from endangered Gentiana, Gentianella, Centaurium, and Swertia species (Gentianaceae): promising natural biotherapeutics

Neuroprotective Xanthones and Their Biosynthesis in Shoot Cultures of Hoppea fastigiata (Griseb.) C.B. Clarke

Xanthones are a class of secondary metabolites produced by plant organisms. They are characterized by a wide structural variety and numerous biological activities that make them valuable metabolites for use in the pharmaceutical field. This review shows the current knowledge of the xanthone biosynthetic pathway with a focus on the precursors and the enzymes involved, as well as on the cellular and organ localization of xanthones in plants. Xanthone biosynthesis in plants involves the shikimate and the acetate pathways which originate in plastids and endoplasmic reticulum, respectively. The pathway continues following three alternative routes, two phenylalanine-dependent and one phenylalanine-independent. All three routes lead to the biosynthesis of 2,3′,4,6-tetrahydroxybenzophenone, which is the central intermediate. Unlike plants, the xanthone core in fungi and lichens is wholly derived from polyketide. Although organs and tissues synthesizing and accumulating xanthones are known in plants, no information is yet available on their subcellular and cellular localization in fungi and lichens. This review highlights the studies published to date on xanthone biosynthesis and trafficking in plant organisms, from which it emerges that the mechanisms underlying their synthesis need to be further investigated in order to exploit them for application purposes.

https://www.mdpi.com/2223-7747/12/4/694/pdf?version=1675500649

Rivaille P

Papers

[On gentiacauleine, a new tetra-substituted xanthone, aglycone of gentiacauloside of Gentiana acaulis L].