Two New Xanthones from the Stems of Garcinia cowa

Cytotoxic and Antiangiogenetic Xanthones Inhibiting Tumor Proliferation and Metastasis from Garcinia xipshuanbannaensis

Eight prenylated xanthones including four new analogues were extracted and purified from the leaves of Garcinia xipshuanbannaensis. Multiple techniques including UV, 1D and 2D NMR, and HRESIMS were used to determine the structures of the isolated xanthones. These xanthones were evaluated for their cytotoxicity toward human cancer cells, and compound 4 exhibited activity against HeLa cells. A cytotoxic mechanism examination revealed the active compound induced cell apoptosis by arresting the cell cycle, increasing the levels of ROS, and inhibiting the expression of p-STAT3 in HeLa cells. In in vivo zebrafish experiments, compound 4 was found to block tumor proliferation and migration and have antiangiogenetic activity, and thus seems worthy of further laboratory evaluation.

Four new xanthones and their cytotoxicity from the stems of Garcinia schomburgkiana

Four new xanthones, named schomburgones C-F (1‒4), along with six known xanthones (5‒10) were isolated from the stems of Garcinia schomburgkiana. Their structures were determined by spectroscopic analysis especially 1D and 2D NMR spectroscopies. The isolated compounds were evaluated for their cytotoxicity against five human cancer cell lines. Furanoxanthones 4‒6 showed potent cytotoxicity against four cell lines (KB, HeLa S3, MCF-7 and Hep G2) with IC₅₀ values in the range of 0.18‒9.95 µM.

Cytotoxic phenolic constituents from Hypericum japonicum

Nine undescribed compounds, including five xanthone derivatives, two flavonoids, one 2-pyrone derivative, and one undescribed naturally occurring compound, along with 30 known phenolic compounds, were isolated from Hypericum japonicum. In addition, hyperjaponols A and B were identified as racemates. The structures and absolute configurations of the undescribed compounds were determined by comprehensive MS, NMR spectroscopy, and electronic circular dichroism (ECD) calculations. The cytotoxic effects of the isolated compounds on two human tumour cell lines (HEL and MDA-MB-231) were evaluated by the MTT assay. Eighteen compounds showed good inhibitory activities against the HEL cell line, with IC₅₀ values of 3.53-18.7 μM, while nine compounds exhibited moderate cytotoxicity against the MDA-MB-231 cancer cell line, with IC₅₀ values ranging from 4.92 to 10.75 μM. Their preliminary structure-activity relationship of the isolated compounds was also discussed.

A pair of new enantiomers of xanthones from the stems and leaves of Cratoxylum cochinchinense

Background

The simple and caged xanthones from Clusiaceae showed significant antineoplastic activity. This study aims to identify structural diverse xanthones and search for novel antitumor natural products from this family plants.

Methods

The structures of new compounds 1a and 1b were elucidated mainly through comprehensive NMR and MS spectroscopic data, and their absolute configurations were determined by the comparison of the experimental and calculated electronic circular dichroism.

Results

A pair of new xanthone enantiomers, (+)- and (-)-cracochinxanthone A (1a and 1b), along with thirty known analogues (2-31), were isolated from extracts of the stems and leaves of C. cochinchinense. Preliminary biological assay of some isolates against HL-60, PC-3, and MDA-MB-231 cancer cell lines.

Conclusion

Some isolated xanthones exhibited high sensitivity against three human malignant cell lines and the structure-activity relationship study showed that the prenyl and geranyl units may play an important role in antitumor activity.

Cytotoxic Xanthones from the Leaves of Garcinia Urophylla

Two new xanthones, 7-hydroxydesoxymorellin (1) and isocaledonixanthone D (2), and four known ones, gaudichaudione H, 1,7-dihydroxy-3-methoxy-2-(3-methyl-2-butenyl)xanthone, 1,5-dihydroxy-3-methoxy-2-(3-methyl-2-butenyl)xanthone, and 1,3,7-trihydroxy-2-(3-methyl-2-butenyl)xanthone, as well as lupeol were isolated from the leaves of Garcinia urophylla (Guttiferae). Their structures were determined using a combination of 1D (1H NMR, 13C NMR, DEPT) and 2D (COSY, gHSQC, gHMBC) NMR spectroscopic techniques. Among the isolates, 7-hydroxydesoxymorellin (1), gaudichaudione H, 1,5-dihydroxy-3-methoxy-2-(3-methyl-2-butenyl)xanthone, and 1,3,7-trihydroxy-2-(3-methyl-2-butenyl)xanthone demonstrated cytotoxic activities against breast (MCF-7), prostate (DU-145), and lung (NCI-H460) human cancer cell lines.

Cytotoxic Properties and Complete Nuclear Magnetic Resonance Assignment of Isolated Xanthones from the Root of Garcinia cowa Roxb

Objective:

To isolate compounds from the roots of Garcinia cowa and to evaluated their cytotoxic activity against breast (MCF-7), prostate (DU-145), and lung (H-460) cell lines.

Materials and Methods:

The ground air-dried root was sequentially macerated with hexane, dichloromethane (DCM), ethyl acetate (EtOAc), and methanol. The DCM soluble extract was fractionated by vacuum liquid chromatography, column chromatography, and radial chromatography over silica gel with hexane, EtOAc and methanol as eluent in progressively increasing polarity manner; to yield three compounds. Their structures were elucidated based on their spectroscopic data and their comparison with those of the literature. The cytotoxicity of isolated compounds was carried out against human cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay. The extract was added at various concentrations (0.1, 1, 10 and 100 mg/ml). The level of cytotoxicity was determined by calculating the level of IC₅₀ that was based on the percentage of the cell death following the 24 h incubation with the extract.

Results:

Phytochemical study on the roots of G. cowa yielded rubraxanthone (3), cowanine (4) and 1,5-dihydroxyxanthone (5). Compound 4 with an IC₅₀ value of 4.1 ± 1.0 μM, 5.4 ± 2.3 μM and 11.3 ± 10.0 μM against MCF-7, H-460, and DU-145, respectively while compound 3 was found to be in active.

Conclusion:

The results indicate that G. cowa roots could be important sources of natural cytotoxic compounds.

SUMMARY

Isolation of cytotoxic compounds from Garcinia cowa

Cowanine is the active constituent from the roots of Garcinia cowa

Complete nuclear magnetic resonance assignment of isolated compounds

MS fragmentation of rubraxanthone.

Xanthones from the Leaves of Garcinia cowa Induce Cell Cycle Arrest, Apoptosis, and Autophagy in Cancer Cells

Two new xanthones, cowaxanthones G (1) and H (2), and 23 known analogues were isolated from an acetone extract of the leaves of Garcinia cowa. The isolated compounds were evaluated for cytotoxicity against three cancer cell lines and immortalized HL7702 normal liver cells, whereby compounds 1, 5, 8, and 15-17 exhibited significant cytotoxicity. Cell cycle analysis using flow cytometry showed that 5 induced cell cycle arrest at the S phase in a dose-dependent manner, 1 and 16 at the G2/M phase, and 17 at the G1 phase, while 16 and 17 induced apoptosis. Moreover, autophagy analysis by GFP-LC3 puncta formation and western blotting suggested that 17 induced autophagy. Taken together, our results suggest that these xanthones possess anticancer activities targeting cell cycle, apoptosis, and autophagy signaling pathways.

Bioactive prenylated xanthones from the young fruits and flowers of Garcinia cowa

Five new xanthones, garciniacowones A-E (1-5), together with 14 known xanthones, 6-19, were isolated from the young fruits and fresh flowers of Garcinia cowa. The structures of 1-5 were elucidated by analysis of their 1D and 2D NMR spectra and mass spectrometric data. The compounds 1-19 were tested in vitro for their antimicrobial activity and for their ability to inhibit α-glucosidase. Compounds 16 and 17 showed the most potent α-glucosidase inhibitory activity, with IC50 values of 7.8 ± 0.5 and 8.7 ± 0.3 μM, respectively. Compounds 8, 9, and 19 showed antibacterial activity against Bacillus subtilis TISTR 088 with identical MIC values of 2 μg/mL, while 8, 10, and 19 exhibited antibacterial activity against Bacillus cereus TISTR 688 with identical MIC values of 4 μg/mL.

Proteasome-inhibitory and cytotoxic constituents of Garcinia lateriflora: absolute configuration of caged xanthones

A new biflavonoid (1), a new xanthone enantiomer (2), five new caged xanthones (3-7), and several known compounds were isolated from the stem bark of Garcinia lateriflora, collected in Indonesia. The structures of the new compounds were determined by analysis of spectroscopic data, and the absolute configuration of the caged xanthones was shown for the first time at carbons 5, 7, 8, 8a, 10a, and 27, by analysis of COSY and NOESY NMR and ECD spectra. The biflavonoids exhibited proteasome inhibitory activity, and the known compound, morelloflavone (8) was found to have the greatest potency (IC(50) = 1.3 muM). The caged xanthones were cytotoxic towards HT-29 cells, with the known compound, morellic acid (10) being the most active (ED(50) = 0.36 muM). However, when tested in an in vivo hollow fiber assay, it was inactive at the highest dose tested (20 mg/kg).

Cowaxanthone F, a new tetraoxygenated xanthone, and other anti-inflammatory and antioxidant compounds from Garcinia cowa

A new tetraoxygenated xanthone, cowaxanthone F (1), as well as four known compounds, morelloflavone (2), volkensiflavone (3), morelloflavone-7″-O-glucoside (fukugiside, 4), and 1,6-dihydroxyxanthone (5), were isolated from the crude acetone extract of the twigs of Garcinia cowa (Guttiferae). All compounds (1–5) were tested for antioxidant activity against DPPH (diphenylpicrylhydrazyl), hydroxyl, and superoxide radicals; only morelloflavone (2) and morelloflavone-7″-O-glucoside (4) exhibited high potency. Eight tetraoxygenated xanthones from the fruits of G. cowa , cowaxanthones A–D (6–9), cowanin (15), α-mangostin (16), mangostanin (17), and cowanol (18), were also investigated for anti-inflammatory activity using ethyl phenylpropiolate (EPP)-induced ear edema. Assessment at 30, 60, and 120 min revealed that cowaxanthones B–D (7–9), cowanin (15), and α-mangostin (16) exhibited significant anti-inflammatory activity when compared to phenylbutazone, while cowaxanthone A (6), mangostanin (17), and cowanol (18) showed less activity.

Bioassay-guided isolation of xanthones and polycyclic prenylated acylphloroglucinols from Garcinia oblongifolia

Bioassay-guided fractionation of the acetone extract of the bark of Garcinia oblongifolia has resulted in the isolation of three new xanthones, oblongixanthones A-C (1-3), three new polyprenylated benzoylphloroglucinols, oblongifolins E-G (4-6), and 12 known compounds. Oblongifolins I (5) and J (6) are the first natural products that have similar structural features to those of two known oxidation products of garcinol. The structures of the new compounds 1-6 were characterized by spectroscopic data interpretation. All isolates were assayed for their apoptosis-inducing effects against HeLa-C3 cells. Oblongifolin C (16) was found to be the most potent apoptotic inducer of the compounds evaluated.

Dulxanthone A induces cell cycle arrest and apoptosisvia up-regulation of p53 through mitochondrial pathway in HepG2 cells

Natural products derived from plants provide a rich source for development of new anticancer drugs. Dulxanthone A was found to be an active cytotoxic component in Garcinia cowa by bioactivity-directed isolation. Studies to elucidate the cytotoxic mechanisms of dulxanthone A showed that dulxanthone A consistently induced S phase arrest and apoptosis in the most sensitive cell line HepG2. Furthermore, p53 was dramatically up-regulated, leading to altered expression of downstream proteins upon dulxanthone A treatment. Cell cycle related proteins, such as cyclin A, cyclin B, cyclin E, cdc-2, p21 and p27 were down-regulated. Some apoptosis correlated proteins were also altered following the drug treatment. Bcl-2 family members PUMA was up-regulated while Bcl-2 and Bax were down-regulated. However, the expression ratio of Bax/Bcl-2 was increased. This resulted in the release of cytochrome C from the mitochondria to the cytosol. Concurrently, Apaf-1 was stimulated with p53 by dulxanthone A. In result, cytochrome C, Apaf-1 and procaspase-9 form an apoptosome, which in turn triggered the activation of caspase-9, caspase-3 and downstream caspase substrates. Lamin A/C and PARP were down-regulated or cleaved, respectively. Moreover, cell cycle arrest and apoptosis in HepG2 cells induced by dulxanthone A were markedly inhibited by siRNA knockdown of p53. In summary, dulxanthone A is an active cytotoxic component of G. cowa. It induces cell cycle arrest at lower concentrations and triggers apoptosis at higher concentrations via up-regulation of p53 through the intrinsic mitochondrial pathway in HepG2 cells. Dulxanthone A is therefore likely a promising preventive and/or therapeutic agent against Hepatoma.