Structure–activity relationships of diverse xanthones against multidrug resistant human tumor cells

Inhibition of Seizure-Like Paroxysms and Toxicity Effects of Securidaca longepedunculata Extracts and Constituents in Zebrafish Danio rerio

Plants used in traditional medicine in the management of epilepsy could potentially yield novel drug compounds with antiepileptic properties. The medicinal plant Securidaca longepedunculata is widely used in traditional medicine in the African continent, and epilepsy is among several indications. Limited knowledge is available on its toxicity and medicinal effects, such as anticonvulsant activities. This study explores the potential in vivo inhibition of seizure-like paroxysms and toxicity effects of dichloromethane (DCM) and ethanol (EtOH) extracts, as well as isolated xanthones and benzoates of S. longepedunculata. Ten phenolic compounds were isolated from the DCM extract. All of the substances were identified by nuclear magnetic resonance spectroscopy. Assays for toxicity and inhibition of pentylenetetrazole (PTZ)-induced seizure-like paroxysms were performed in zebrafish larvae. Among the compounds assessed in the assay for maximum tolerated concentration (MTC), benzyl-2-hydroxy-6-methoxy-benzoate (MTC 12.5 μM), 4,8-dihydroxy-1,2,3,5,6-pentamethoxyxanthone (MTC 25 μM), and 1,7-dihydroxy-4-methoxyxanthone (MTC 6.25 μM) were the most toxic. The DCM extract, 1,7-dihydroxy-4-methoxyxanthone and 2-hydroxy-1,7-dimethoxyxanthone displayed the most significant inhibition of paroxysms by altering the locomotor behavior in GABAA receptor antagonist, PTZ, which induced seizures in larval zebrafish. The EtOH extract, benzyl benzoate, and benzyl-2-hydroxy-6-methoxy-benzoate unexpectedly increased locomotor activity in treated larval zebrafish and decreased locomotor activity in nontreated larval zebrafish, seemingly due to paradoxical excitation. The results reveal promising medicinal activities of this plant, contributing to our understanding of its use as an antiepileptic drug. It also shows us the presence of potentially new lead compounds for future drug development.

Xanthones and benzophenones isolated from the endophytic fungus Penicillium sp. ct-28 of Corydlis tomentella and their cytotoxic activity

One new xanthone, griseophenexanthone A (1), one new benzophenone, digriseophene A (2), and 14 previously reported compounds were isolated from the culture of Penicillium sp. ct-28, an endophytic fungus of Corydlis tomentella. The structures of the isolated compounds were identified by an extensive analysis of HRESIMS, 1D and 2D NMR. MTT assay showed that six xanthones (1 and 3-7) significantly inhibited cell proliferation in four cancer cell lines, with IC₅₀ values ranging from 18.12 ± 2.42 to 85.55 ± 7.66 μM. Our results showed that slight structural changes led to obvious activity differences among these compounds. We also investigated the effects of the six xanthones on cell cycle and apoptosis in human hepatoma HepG2 cells. Compound 7 caused cell cycle arrest at G1 phase, compounds 5 and 6 caused cell cycle arrest at S phase, whereas compounds 1, 3 and 4 had no effects on cell cycle distribution. All six xanthones induced apoptosis in dose-dependent manners in HepG2 cells accompanied by degradation of PARP and activation of caspase 3. The structure-activity relationship analysis revealed that the effects of these xanthones on cell cycle and apoptosis in HepG2 cells were closely related to the substituent groups on their skeleton. Our studies provide novel insights for the structural optimization of xanthones in the development of new anticancer drugs.

SMILES-based QSAR and molecular docking study of xanthone derivatives as α-glucosidase inhibitors

Increasing diabetic population is one of the major health concerns all over the world. Inhibition of α-glucosidase is a clinically proved and attractive strategy to manage diabetes. In this study, robust and reliable QSAR models to predict α-glucosidase inhibitory potential of xanthone derivatives are developed by the Monte Carlo technique. The chemical structures are represented by SMILES notation without any 3D-optimization. The significance of the index of ideality correlation (IIC) with applicability domain (AD) is also studied in depth. The models developed using CORAL software by considering IIC criteria are found to be statistically more significant and robust than simple balance of correlation. The QSAR models are validated by both internal and external validation methods. The promoters of increase and decrease of activity are also extracted and interpreted in detail. The interpretation of developed models explains the role of different structural attributes in predicting the pIC₅₀ of xanthone derivatives as α-glucosidase inhibitors. Based on the results of model interpretation, modifications are done on some xanthone derivatives and 15 new molecules are designed. The α-glucosidase inhibitory activity of novel molecules is further supported by docking studies.

Tandem synthesis of 4-aminoxanthones is controlled by a water-assisted tautomerization: a general straightforward reaction

Iminolactone-aminofuran tautomerization is the rate-determining step in the multicomponent synthesis of xanthones from 3-carbonylchromones, isocyanides and dienophiles.

Synthesis and antitumor, antityrosinase, and antioxidant activities of xanthone

Ten substituted 1,3-dihydroxyxanthones were synthesized in one step. The yields ranged from 40 to 76%. Compounds 8-10 were first reported. Next, the compounds' in vitro anti-proliferative activities against nine human cancer cell lines, antityrosinase, and antioxidant activities were evaluated. Compounds 1, 4, 6-7, and 9-10 exhibited enhanced cytotoxicity against certain cancer cells. Compounds 2, 8, 9, and 10 inhibited tyrosinase activity to a certain extent. In addition, compound 4 exhibited the best antioxidant activity, which was consistent with theoretical calculations. These results demonstrated that compounds 1-2, 4, and 6-10 were promising leads for further investigation.

Design, synthesis and cardiovascular evaluation of some aminoisopropanoloxy derivatives of xanthone

A series of aminoisopropanoloxy derivatives of xanthone has been synthesized and their pharmacological properties regarding the cardiovascular system has been evaluated. Radioligand binding and functional studies in isolated organs revealed that title compounds present high affinity and antagonistic potency for α₁-(compound 2 and 8), β-(compounds 1, 3, 4, 7), α₁/β-(compounds 5 and 6) adrenoceptors. Furthermore, compound 7, the structural analogue of verapamil, possesses calcium entry blocking activity. The title compounds showed hypotensive and antiarrhythmic properties due to their adrenoceptor blocking effect. Moreover, they did not affect QRS and QT intervals, and they did not have proarrhythmic potential at tested doses. In addition they exerted anti-aggregation effect. The results of this study suggest that new compounds with multidirectional activity in cardiovascular system might be found in the group of xanthone derivatives.