Cytotoxic constituents from the roots of Tovomita brevistaminea

13C NMR dereplication-assisted isolation of bioactive polyphenolic metabolites from Clusia flava Jacq

Presently it is estimated that many of the approximately 4000 new natural products isolated every year following complicated, long, and expensive isolation processes are already known; because of this, developing new strategies for locating secondary metabolites of interest in complex extracts or fractions is important. Currently, chromatographic and spectroscopic techniques are being used to optimize the isolation and identification of natural products. In this investigation we have used 13C NMR dereplication analyses for the quick identification of a number of triterpenes (friedelin, lupeol, betulinic acid), sterols (euphol, β-sitosterol) and fatty acids (palmitic acid) present in semipurified fractions obtained from the stem bark extract of Clusia flava and to assist in the isolation of the bioactive metabolites trapezifolixanthone and paralycolin A. The complete and correct assignment of the 1H and 13C NMR spectroscopic data for paralycolin A is reported for the first time and the antioxidant and antiAGEs activity of both metabolites is described.

Label-free biosensing of lignans for therapeutics using engineered model surfaces

The label-free interaction analysis of macromolecules and small molecules has increasing importance nowadays, both in diagnostics and therapeutics. In the blood vascular system, human serum albumin (HSA) is a vital globular transport protein with potential multiple ligand binding sites. Characterizing the binding affinity of compounds to HSA is essential in pharmaceutics and in developing new compounds for clinical application. Aryltetralin lignans from the roots of Anthriscus sylvestris are potential antitumor therapeutic candidates, but their molecular scale interactions with specific biomolecules are unrevealed. Here, we applied the label-free grating-coupled interferometry (GCI) biosensing method with a polycarboxylate-based hydrogel layer with immobilized HSA on top of it. With this engineered model surface, we could determine the binding parameters of two novel aryltetralin lignans, deoxypodophyllotoxin (DPT), and angeloyl podophyllotoxin (APT) to HSA. Exploiting the multi-channel referencing ability, the unique surface sensitivity, and the throughput of GCI, we first revealed the specific biomolecular interactions. Traditional label-free kinetic measurements were also compared with a novel, fast way of measuring affinity kinetics using less sample material (repeated analyte pulses of increasing duration (RAPID)). Experiments with well-characterized molecular interactions (furosemide to carbonic-anhydrase (CAII) and warfarin, norfloxacin to HSA) were performed to prove the reliability of the RAPID method. In all investigated cases, the RAPID and traditional measurement gave similar affinity values. In the case of DPT, the measurements and relevant modeling suggested two binding sites on HSA, with dissociation constant values of K_d1 = 1.8 ± 0.01 μM, K_d2 = 3 ± 0.02 μM. In the case of APT, the experiments resulted in K_d1 = 9 ± 1.7 μM, K_d2 = 28 ± 0.3 μM. The obtained binding values might suggest the potential medical application of DPT and APT without further optimization of their binding affinity to HSA. These results could be also adapted to other biomolecules and applications where sample consumption and the rapidity of the measurements are critical.

Nitric oxide inhibitory xanthones from the pericarps of Garcinia mangostana

Mangosteen (Garcinia mangostana, Clusiaceae) is called "queen of fruit" in Southeast Asia. In the current study, three dimeric xanthones, garcinoxanthones A-C, and four monomeric xanthones, garcinoxanthones D-G, together with 18 known xanthones, were isolated from the pericarps of G. mangostana, collected in Thailand. The structures of garcinoxanthones A-G were elucidated by analysis of their 1D and 2D NMR and other spectroscopic data, and their absolute configurations were determined by the CD spectra. All seven compounds were tested for nitric oxide (NO) inhibitory activity on lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Garcinoxanthones B and C significantly inhibited NO production with IC₅₀ values of 11.3 ± 1.7 and 18.0 ± 1.8 μM, respectively, which were comparable with the positive control indomethacin (IC₅₀ 3.9 ± 0.3 μM). Moreover, garcinoxanthone B suppressed inducible NO synthase expression in a dose-dependent manner. These results reveal the presence of rare dimeric xanthones in G. mangostana and their NO inhibitory effect on LPS-stimulated murine macrophage cells.

Phytochemistry and Pharmacology of the Genus Tovomita

The genus Tovomita (Fam. Clusiaceae) comprises 45 species mainly found in tropical regions of Central and South America. Most of the species of the title genus have been used for centuries as natural remedies. Phytochemicals isolated from Tovomita spp. include prenylated and unprenylated benzophenones and xanthones. The aim of this review is to examine in detail from a phytochemical and pharmacological point of view what is reported in the past and current literature about the properties of phytopreparations and individual active principles obtained from plants belonging to the Tovomita genus.

Antimicrobial prenylated benzoylphloroglucinol derivatives and xanthones from the leaves of Garcinia goudotiana

Bioassay-guided fractionation using antimicrobial assay of the crude acetonic extract of Garcinia goudotiana leaves and of its five partitions led to the isolation of two new prenylated benzoylphloroglucinol derivatives, goudotianone 1 (1) and goudotianone 2 (2), in addition to two known compounds including one xanthone, 1,3,7-trihydroxy-2-isoprenylxanthone (3), and one triterpenoid, friedelin (4). Their structures were elucidated on the basis of different spectroscopic methods, including extensive 1D- and 2D-NMR spectroscopy and mass spectrometry. The crude acetonic extract, the methylene chloride and ethyl acetate partitions, and some tested compounds isolated from this species (1-3) demonstrated selective significant antimicrobial activities against Gram-positive bacteria, in particular Staphylococcus lugdunensis, Enterococcus faecalis and Mycobacterium smegmatis. The potential cytotoxic activities of these extracts and compounds were evaluated against human colon carcinoma HT29 and human fetal lung fibroblast MRC5 cells.

Two new xanthones from Calophyllum nodusum (Guttiferae)

The air-dried powdered stem bark of Calophyllum nodusum (Guttiferea) collected from Sandakan (Sabah, Malaysia), was extracted sequentially with hexane, chloroform and methanol. The solvents were removed by rotary evaporator to give dark viscous extracts. Detailed and repeated chromatographic separation of the extracts lead to isolation of two new xanthones, identified as nodusuxanthone (1a) and trapezifolixanthone A (2). Other common terpenoids such as betulinic acid, lupeol, stigmasterol and friedelin were also isolated from the extracts and identified. The structures of the compounds were established by detailed spectral analysis and comparison with previously reported data.

Relationships between inhibitory activity against a cancer cell line panel, profiles of plants collected, and compound classes isolated in an anticancer drug discovery project

In an attempt to determine the relationships between the plant profiles (country of collection, taxonomy, plant part) and the compound classes isolated with cytotoxic activity against a panel of human tumor cell lines, the data compiled from a 15-year anticancer drug-discovery project were subjected to an analysis of variance (ANOVA). The results indicate significant trends in cytotoxic activity relative to collection location, taxonomy, plant part, and compound classes isolated. Plant collections were made in tropical forests in six countries, with collections from Ecuador resulting in higher activity than those from Indonesia and Peru. Interestingly, collections from Florida were not statistically different than those from the countries with higher biodiversity. One hundred and forty-five families were represented in the collections, with the Clusiaceae, Elaeocarpaceae, Meliaceae, and Rubiaceae having low ED50 (half maximal effective dose) values. Especially active genera included Aglaia, Casearia, Exostema, Mallotus, and Trichosanthes. Roots and below-ground plant materials were significantly more active than above-ground materials. Cucurbitacins, flavaglines, anthraquinones, fatty acids, tropane alkaloids, lignans, and sesquiterpenoids were significantly more active than xanthones and oligorhamnosides. The results from this study should serve as a guide for future plant collection endeavors for anticancer drug discovery.

Antibacterial and cytotoxic activity of Brazilian plant extracts--Clusiaceae

Twelve extracts obtained from nine plants belonging to six different genera of Clusiaceae were analyzed against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Enterococcus faecalis) bacteria using the microdilution broth assay. Tovomita aff. longifolia, T. brasiliensis, Clusia columnaris, Garcinia madruno, Haploclathra paniculata, and Caraipa grandifolia extracts showed significant results against the bacteria. The organic extract obtained from the leaves of T. aff. longifolia showed minimal inhibitory concentration (MIC) = 70 microg/ml and minimal bactericidal concentration (MBC) = 90 microg/ml against E. faecalis and the organic extract made with the stem of C. columnaris showed MIC = 180 microg/ml and MBC = 270 microg/ml against P. aeruginosa. None of the antibacterial extracts showed lethal activity against brine shrimp nauplii. On the other hand, both aqueous and organic extracts obtained from the aerial organs of Vismia guianensis that were cytotoxic to brine shrimp nauplii did not show a significant antibacterial activity in the assay.

Dichromenoxanthones from Tovomita brasiliensis

Two dichromenoxanthones [1,6-dihydroxy-6',6'-dimethylpyrano(2',3':3,4)-6'',6''-dimethylpyrano(2'',3'':7,8)xanthone (brasilixanthone A) and 1,6-dihydroxy-6',6'-dimethylpyrano(2',3':2,3)-6'',6''-dimethylpyrano(2'',3'':7,8)xanthone (brasilixanthone B)], along with betulinic acid, friedelin, sitosterol and stigmasterol were isolated from the roots and stems of Tovomita brasiliensis. Their structures were characterized on the basis of 1H and 13C NMR spectral data, including 2D NMR experiments.

New bioactive aromatic compounds from Vismia guianensis

Five benzophenones, vismiaguianones A-E, and two benzocoumarins, vismiaguianins A and B were isolated from the CHCl3 extract of the roots of Vismia guianensis by bioassay-directed fractionation using the DNA strand-scission assay and KB cell line. Of the isolates obtained, vismiaguianone B exhibited DNA strand-scission activity, whereas vismiaguianones D and E and vismiaguianin A were found to be significantly cytotoxic.