Bioactive Marine Xanthones: A Review

The marine environment is an important source of specialized metabolites with valuable biological activities. Xanthones are a relevant chemical class of specialized metabolites found in this environment due to their structural variety and their biological activities. In this work, a comprehensive literature review of marine xanthones reported up to now was performed. A large number of bioactive xanthone derivatives (169) were identified, and their structures, biological activities, and natural sources were described. To characterize the chemical space occupied by marine-derived xanthones, molecular descriptors were calculated. For the analysis of the molecular descriptors, the xanthone derivatives were grouped into five structural categories (simple, prenylated, O-heterocyclic, complex, and hydroxanthones) and six biological activities (antitumor, antibacterial, antidiabetic, antifungal, antiviral, and miscellaneous). Moreover, the natural product-likeness and the drug-likeness of marine xanthones were also assessed. Marine xanthone derivatives are rewarding bioactive compounds and constitute a promising starting point for the design of other novel bioactive molecules.

An Update on the Anticancer Activity of Xanthone Derivatives: A Review

The annual number of cancer deaths continues increasing every day; thus, it is urgent to search for and find active, selective, and efficient anticancer drugs as soon as possible. Among the available anticancer drugs, almost all of them contain heterocyclic moiety in their chemical structure. Xanthone is a heterocyclic compound with a dibenzo-γ-pyrone framework and well-known to have “privileged structures” for anticancer activities against several cancer cell lines. The wide anticancer activity of xanthones is produced by caspase activation, RNA binding, DNA cross-linking, as well as P-gp, kinase, aromatase, and topoisomerase inhibition. This anticancer activity depends on the type, number, and position of the attached functional groups in the xanthone skeleton. This review discusses the recent advances in the anticancer activity of xanthone derivatives, both from natural products isolation and synthesis methods, as the anticancer agent through in vitro, in vivo, and clinical assays.

Synthesis and Biological Evaluation of Xanthone Derivatives as Anti-Cancer Agents Targeting Topoisomerase II and DNA

Topoisomerase is one of the most important targets of anticancer drugs. In order to develop effective and low-toxic topoisomerase inhibitors, a series of xanthone derivatives have been designed and synthesized using the principles of skeleton transition. In vitro growth inhibition experiments of human breast cancer(MCF-7), gastric cancer (MGC-803), and cervical cancer(Hela) cell lines were used to evaluate the compound's anti-tumor cell proliferation activity. Most of the compounds showed anti-tumor growth activity, and also showed low toxicity to human normal cells L929. In the enzyme activity inhibition experiment, compounds 7d and 8d showed the best inhibitory activity. The DNA binding studies disclosed that the most potent compounds 7d and 8d can intercalate into DNA, induce apoptosis in MGC-803 cells and arrested at G2/M phase. Molecular docking showed that compounds 7d and 8d could bind with topoisomerase II and DNA through hydrogen bonds and π-stacking interactions.

Novel Xanthone Derivatives Impair Growth and Invasiveness of Colon Cancer Cells In Vitro

Natural xanthones are a large group of compounds from which promising anticancer properties could be further developed by chemical modifications. This study aimed to investigate the influence of four novel xanthone derivatives based on a naturally occurring xanthone skeleton on the invasiveness of colon cancer cells in vitro. First, the concentrations required to inhibit growth of three colorectal cancer cell lines to 50% (GI50) of all the studied compounds, as well as the natural xanthones used as a reference (gambogic acid and α-mangostin), have been established (MTS reduction test). Next, the assays determining several aspects of the GI25 xanthones influence on colorectal cancer cells, including cytotoxicity, migration and invasion potential, interaction with extracellular matrix and endothelial cells, as well as expression of selected invasiveness related genes have been performed. Our results demonstrate that these novel xanthone derivatives impair colorectal cancer proliferation, motility, adhesion to extracellular matrix and to endothelial cells, and also induce apoptosis and cell death. Moreover, their activity is comparable to cisplatin and 5-fluorouracil, used as reference compounds. Conducted research indicates our compounds for further research and development as novel drugs in colorectal cancer treatment.

Synthesis of 1-Hydroxy-3-O-Substituted Xanthone Derivatives and their Structure-activity Relationship on Acetylcholinesterase Inhibitory Effect

Xanthones are valuable compounds in drug design and development, attributed to their multi-dimensional pharmacological properties, including anti-cancer, anti-bacterial, anti-malarial, anti-inflammatory and anti-cholinesterase. This study focused on the synthesis of 1,3-dihydroxyxanthone (1) and its new 1-hydroxy-3-O-substituted derivatives with alkyl (2a-2f), alkenyl (2g-2k), alkynyl (2l-2n) and alkylated phenyl (2o-2r) groups and were synthesised in a high percentage yield of >70%, except for 2l and 2p. Their structures were confirmed by MS, NMR and FTIR spectroscopic techniques. The evaluation of acetylcholinesterase (AChE) inhibitory activities showed that all the substituted xanthones (2a-2r) are more potent than 1. Compounds 2g and 2j are the strongest AChE inhibitors with the IC50 values of 20.8 and 21.5 μM and their enzyme kinetic analyses indicated that these derivatives possess a mixed-mode inhibition, where they targeted both the active sites and allosteric sites of AChE. Molecular docking study revealed that 2g binds favourably to the active site of AChE via π–π stacking and hydrogen bonding, in addition to π-alkyl interaction and alkyl interaction from the substituent group. The xanthone derivatives are identified as potential lead compounds for further development of Alzheimer’s disease treatments.

Design, Synthesis, Computational and Biological Evaluation of Two New Series of 1, 3- and 1,6-dihydroxy xanthone Derivatives as Selective COX-2 Inhibitors

Background: Over the years, the xanthone nucleus has been serving as an interesting scaffold for the design of derivatives aiming at anti-inflammatory drug development. Objective: The objective of the current work was to design and synthesize two series of novel 3-(5'-substituted pentyloxy)-1-hydroxy xanthone & 6-(5'-substitutedpentyloxy)-1-hydroxy xanthone derivatives. The designed compounds were examined in vivo for anti-inflammatory activity. The effect of the synthesized xanthone derivatives on the serum expression of IL-10 and TNF-α was evaluated to understand the underlying molecular mechanisms. Method: The title compounds were virtually designed and screened for ADME/T properties and docked onto the COX-2 protein. The synthesis of the xanthone derivatives was achieved by the condensation of salicylic acid derivatives and a suitable phenol in presence of a mixture of phosphorus pentoxide–methanesulfonic acid as an acylation catalyst. The compounds were evaluated for in vivo anti-inflammatory activity by carrageenan induced paw edema method and serum expression of cytokines was evaluated using ELISA assays. Results: The selected compounds exhibited docking scores ranging between -10.7 to -6.8 (Kcal/mol) respectively as compared with standard Celecoxib (-7.9 Kcal/mol) and the non-selective COX inhibitor Indomethacin (-6.4 Kcal/mol). Among the tested compounds 9u have shown the highest activity with 65.6 % reduction in edema (69.8% for Celecoxib). Immunoassay results showed a significant drop in serum TNF-α and an elevation in serum IL-10. Conclusion: The findings highlight the fact that some of the synthesized xanthone derivatives displayed marked anti-inflammatory activity which can be further investigated to render efficient and novel non-ulcerogenic anti-inflammatory agents.

From Natural Products to New Synthetic Small Molecules: A Journey through the World of Xanthones

This work reviews the contributions of the corresponding author (M.M.M.P.) and her research group to Medicinal Chemistry concerning the isolation from plant and marine sources of xanthone derivatives as well as their synthesis, biological/pharmacological activities, formulation and analytical applications. Although her group activity has been spread over several chemical families with relevance in Medicinal Chemistry, the main focus of the investigation and research has been in the xanthone family. Xanthone derivatives have a variety of activities with great potential for therapeutic applications due to their versatile framework. The group has contributed with several libraries of xanthones derivatives, with a variety of activities such as antitumor, anticoagulant, antiplatelet, anti-inflammatory, antimalarial, antimicrobial, hepatoprotective, antioxidant, and multidrug resistance reversal effects. Besides therapeutic applications, our group has also developed xanthone derivatives with analytical applications as chiral selectors for liquid chromatography and for maritime application as antifouling agents for marine paints. Chemically, it has been challenging to afford green chemistry methods and achieve enantiomeric purity of chiral derivatives. In this review, the structures of the most significant compounds will be presented.