Synthesis and Cytotoxic Activity of Benzo[a]pyrano[3,2-h] and [2,3-i]xanthone Analogues of Psorospermine, Acronycine, and Benzo[a]acronycine

Deconstructive annulation mediated one-pot synthesis of xanthene derivatives

Direct conversion of naphthoxazines to diverse xanthene derivatives was achieved under one-pot operation through deconstructive annulation methodology. Sequential oxidative C(sp3)-O/C(sp3)-N cleavage followed by intramolecular/intermolecular annulation reaction was carried out under aerobic reaction conditions. Mechanistic analyses performed on the substrate revealed that the C(sp3)-O bond cleavage supersedes the C(sp3)-N bond scission. The in situ generated Betti base intermediate through the C(sp3)-O cleavage was successfully isolated. Based on a molecular docking investigation, the intermolecular annulated products demonstrated good α-glucosidase inhibitory properties.

Xanthone-1,2,4-triazine and Acridone-1,2,4-triazine Conjugates: Synthesis and Anticancer Activity

A total of 21 novel xanthone and acridone derivatives were synthesized using the reactions of 1,2,4-triazine derivatives with 1-hydroxy-3-methoxy-10-methylacridone, 1,3-dimethoxy-, and 1,3-dihydroxanthone, followed by optional dihydrotiazine ring aromatization. The synthesized compounds were evaluated for their anticancer activity against colorectal cancer HCT116, glioblastoma A-172, breast cancer Hs578T, and human embryonic kidney HEK-293 tumor cell lines. Five compounds (7a, 7e, 9e, 14a, and 14b) displayed good in vitro antiproliferative activities against these cancer cell lines. Compounds 7a and 7e demonstrated low toxicity for normal human embryonic kidney (HEK-293) cells, which determines the possibility of further development of these compounds as anticancer agents. Annexin V assay demonstrated that compound 7e activates apoptotic mechanisms and inhibits proliferation in glioblastoma cells.

Design and synthesis of gambogic acid analogs as potent cytotoxic and anti-inflammatory agents

Prenyl- and pyrano-xanthones derived from 1,3,6-trihydroxy-9H-xanthen-9-one, a basic backbone of gambogic acid (GA), were synthesized and evaluated for in vitro cytotoxic effects against four human cancer cell lines (KB, KBvin, A549, and DU-145) and anti-inflammatory activity toward superoxide anion generation and elastase release by human neutrophils in response to fMLP/CB. Among them, prenylxanthones 7-13 were generally less active than pyranoxanthones 14-21 in both anticancer and anti-inflammatory assays. Furthermore, two angular 3,3-dimethypyranoxanthones (16 and 20) showed the greatest and selective activity against the KBvin multidrug resistant (MDR) cell line with IC(50) values of 0.9 and 0.8 μg/mL, respectively. An angular 3-methyl-3-prenylpyranoxanthone (17) selectively inhibited elastase release with 200 times more potency than phenylmethylsulfonyl fluoride (PMSF), the positive control.

Cytotoxic activity and DNA-binding properties of xanthone derivatives

In this study, the interactions of different groups substituted xanthone derivatives with calf thymus DNA (ct DNA) have been investigated by spectrophotometric methods and viscosity measurements. Results indicate that xanthone derivatives can intercalate into the DNA base pairs by the plane of xanthone ring and the various substituents may influence the binding affinity with DNA according to the calculated quenching constant values and the melting temperature of DNA. Furthermore, three tumor cell lines including esophagus squamous cancer cell line (ECA109), stomach cancer cell line (SGC7901) and lung cancer cell line (GLC-82) have been used to evaluate the cytotoxic activities of xanthone derivatives by MTT (microculture tetrazolium) method. Analysis show that the oxiranylmethoxy or piperidinylethoxy substituted xanthones exhibit more effective cytotoxic activity against three cancer cells than the other substituted xanthones. The effects on the inhibition of tumor cells in vitro agree with the studies of DNA-binding.

Antitumor psoropermum xanthones and sarcomelicope acridones: privileged structures implied in DNA alkylation

Fused isopropylfuran and dimethylpyran units are privileged structures present in numerous bioactive natural products exemplified, in the field of anticancer drugs, by the furanoxanthone psorospermin and the pyranoacridone acronycine. Psorospermin binds to the N-7 position of the guanine units in the presence of topoisomerase II. In contrast, acronycine derivatives such as cis-1,2-diacetoxy-1,2-dihydrobenzo[b]acronycine alkylate the 2-amino group of DNA guanine residues in the minor groove. Hybrid compounds associating the acridone or benzo[b]acridone chromophore of acronycine derivatives and the epoxyfuran alkylating unit present in psorospermin also display very potent antiproliferative activities, alkylating DNA guanine units at position N-7 in the major groove, as natural xanthones belonging to the psorospermin series.

Synthesis of xanthone derivatives with extended π-systems as α-glucosidase inhibitors: Insight into the probable binding mode

A series of novel xanthone derivatives with extended pi-systems, that is, benzoxanthones 2-4, and their structurally perturbed analogs 5-9 have been designed and synthesized as alpha-glucosidase inhibitors. Their inhibitory activities toward yeast's alpha-glucosidase were evaluated with the aim to enrich the structure-activity relationship. The results indicated that benzoxanthones 2-4 were capable of inhibiting in vitro yeast's alpha-glucosidase 17- to 28-fold more strongly than xanthone derivative 1 that has smaller conjugated pi-system. Benzoxanthone 8, bearing angularly fused aromatic rings, and reduced benzoxanthone 5 showed decreased activities, strongly suggesting that linearly conjugated pi-systems play a crucial role in the inhibition process. O-Methylation of 3-OH of benzoxanthone 2 and nitration at C4 position led to a large decrease in the activity. This indicates that 3-OH of benzoxanthone was crucial to the inhibitory activity, primarily as an H-bonding donor. The present results suggest that pi-pi stacking effect and H-bonding make substantial contributions to elicit the inhibitory activities of this general class of inhibitors.