Vol 11, Issue 2, 2018 Online - 2455-3891 Print - 0974-2441 SYNTHESIS AND BIOLOGICAL PROPERTIES OF PHARMACEUTICALLY IMPORTANT XANTHONES AND BENZOXANTHONE ANALOGS: A BRIEF REVIEW POOJA BEDI, RICHA GUPTA, TANAY PRAMANIK* Department of Chemistry, Faculty of Technology and Sciences, School of Chemical Engineering and Physical Science, Lovely Professional University, Phagwara, Punjab, India. Email: Tanay.pramanik@gmail.com Received: 06 September 2017, Revised and Accepted: 30 October 2017 ABSTRACT 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 such as fungi, ferns, and lichens. Synthetic analogs of xanthones have shown a large number of pharmacological properties such as antioxidant, anti-inflammatory, antidiabetics, antihistamine, antitumoral, antiulcer, and algicidal. Moreover, they also find usages in photodynamic therapy, laser technology, and dyes. This review lays stress on various solvents, catalyst and synthetic route for synthesis of xanthones, benzoxanthones analogs. The review has also focused on the classifications of xanthone as well as extensively studied biological properties of the xanthones and benzoxanthones analogs. Keywords: Multicomponent reactions, Xanthones, Benzoxanthones, Biological properties. INTRODUCTION During the past few decades, there has been widespread interest in multicomponent reactions (MCRs) due to their increasing importance in organic and medicinal chemistry [1-3]. MCRs are the processes in which three or more reactants are combined in a single step to yield products by combining suitable portions of all the reactants. These reactions are very effective in synthesizing highly functionalized small organic molecules from easily available starting materials in a single step and in short duration of time period. MCR also provides a higher overall percentage of yield. Thus these reactions reduces labor by reducing a number of synthetic operations such as extraction, purification, and generates lesser amount of waste as compare to conventional multistep reactions of a complex molecule [4-6]. A large number of MCRs are already known, and the searches for new MCRs are still on. One such reaction which belongs to MCR category is a synthesis of xanthones and its derivatives with extended conjugation, i.e., Benzoxanthones. Xanthones are naturally occurring polyphenolic compounds. Xanthone nucleus is the main framework of large number of natural and synthetic materials. These are parent of several natural yellow pigments. These comprise an important class of oxygenated heterocycles. Xanthone Skelton possesses good thermal oxidative and hydrolytic stability, that’s why these are considered as structural motif in high performance and engineering polymers [7]. Numerous derivatives of xanthones are isolated from higher plants, fungi, and lichens [8]. However, the naturally occurring xanthones are limited to a fewer number of substituent, so efforts are made to synthesize them from their constituent fragments. Xanthones and benzoxanthones constitute an important class of biologically active heterocycles. Due to their remarkable pharmacological and biological applications, their synthesis has drawn great attention in the field of medicinal and pharmaceutical chemistry. They possess antiviral [9], anti-inflammatory [10], antibacterial [11], antimalarial [12], anti-HIV [13], antimicrobial, antioxidant, and anticarcinogenic [14,15] activities. These are also used as an antagonist for paralyzing action of zoxazolamine [16]. Furthermore, these compounds can be used in photodynamic therapy [17], as dyes [18] in laser technology [19] and in fluorescent materials which are sensitive to pH for visualization of biomolecules [20]. Classification of xanthone Naturally occurring xanthones are broadly classified into six categories: 1. Simple oxygenated xanthone. 2. Xanthone glycosides. 3. Prenylated xanthone. 4. Bisxanthones. 5. Xantholignoids. 6. Miscellaneous xanthones. Simple oxygenated xanthone These xanthones carry simple hydroxyl, methoxy, and methyl groups. These are further subdivided into various categories such as mono, di, tri, tetra, penta, and hexa oxygenated depending on the level of oxygenation [21-23]. For example, 2-hydroxyxanthone (3), 2-hydroxy- 1-methoxyxanthone (4). Xanthone glycosides The xanthone in which sugar moiety is attached to xanthone nucleus is called xanthone glycosides. These are further of two types, i.e., C-glycosides and O-glycosides. In C-glycosides sugar moiety is attached to xanthone nucleus by C-C bond whereas in O-glycosides glycosidic linkage, i.e. C-O-C joins sugar moiety to xanthone. C-glycosides are fewer in number as compare to O-glycosides. For example, mangiferin (22) and isomangiferin are most common C-glycosides, and Swertia japonica (24) and gentioside are few O-glycosides. Prenylated xanthone These are the xanthones in which 5-carbon unit such as isoprenyl and 1,1-dimethylprop-2-enyl,3-hydroxy-3-methylbutyl [24-26] is attached as a substituent to xanthone nucleus, for example, © 2018 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons. org/licenses/by/4. 0/) DOI: http://dx.doi.org/10.22159/ajpcr.2018.v11i2.22426 Review Article