Antifungal activity of extracts and prenylated coumarins isolated from Baccharis darwinii Hook & Arn. (Asteraceae)

The petroleum ether extract of Baccharis darwinii showed activity against Cryptococcus neoformans and dermatophytes. Bioactivity-guided fractionation of Baccharis darwinii has resulted in the isolation of three coumarins: 5'-hydroxy aurapten (anisocoumarin H, 1), aurapten (7-geranyloxycoumarin, 2) and 5'-oxoaurapten (diversinin, 3). The structures of these compounds were characterized by spectroscopic methods. These compounds were evaluated for their antimicrobialactivity against a panel of each, bacteria and fungi. Compound 3 showed the best activities against Microsporum gypseum, Trichophyton rubrum and Trichophyton mentagrophytes with MICs = 15.6 microg/mL, followed by compound 1 whose MICs against the same fungi were 62.5 microg/mL. In addition they showed fungicidal rather than fungistatic activity. Both compounds showed moderate activity (MICs = 125 microg/mL) against Cryptococcus neoformans. This is the first report of the presence of compound 1 in B. darwinii.

Purification and identification of antibacterial phenolics from Tripodanthus acutifolius leaves

AIMS

To perform an activity-guided purification, identification and quantification of antibacterial compounds from Tripodanthus acutifolius infusion. To validate the antibacterial activity of purified substances.

METHODS AND RESULTS

Bioautographic methods were employed as screening assays for purifying bioactive substances. Purification procedures included sephadex LH-20 column chromatography and reverse phase HPLC. Identification was achieved by spectroscopic methods (UV-Vis, MS, NMR and polarimetry) and chromatographic assays (paper chromatography and HPLC). Antibacterial activity was studied by microdilution, colony count and photometric assays, Sytox green stain and transmission electron microscopy (TEM). Four glycoflavonoids (rutin, nicotiflorin, hyperoside and isoquercitrin) and an unusual phenylbutanoid glycoside (tripodantoside) were purified and identified. Tripodantoside was found at 6.59 +/- 0.82 g per 100 g of dry leaves. The flavonoids showed bactericidal effect at a concentration of 4 mg ml(-1) against Staphylococcus aureus and Pseudomonas aeruginosa strains from American Type Culture Collection, while tripodantoside was almost four times more active than those compounds, with a minimum bactericidal concentration = 1.024 mg ml(-1) against these strains. Tripodantoside aglycone showed bacteriolytic effects on the assayed strains, causing evident damages on cell wall and membrane, while tripodantoside did not exhibit those effects.

CONCLUSIONS

The antibacterial activity of T. acutifolius infusion would be partially attributed to the purified glycoflavonoids and mainly to tripodantoside.

SIGNIFICANCE AND IMPACT

The high extraction yield and the antibacterial activity exhibited by tripodantoside makes this chemical structure of interest to support further studies dealing with chemical modifications to increase the antibacterial activity or to seek another activities.

Chemically engineered extracts: bioactivity alteration through sulfonylation

The chemical composition and the biomolecular properties of a series of crude plant extracts were altered without previous knowledge of their detailed chemical composition.

Chemically engineered extracts as an alternative source of bioactive natural product-like compounds

The access to libraries of molecules with interesting biomolecular properties is a limiting step in the drug discovery process. By virtue of a long molecular evolution process, natural products are recognized as biologically validated starting points in structural space for library development. We introduce here a strategy to generate natural product-like libraries. A semisynthetic mixture of compounds was produced by diversification of a natural product extract through the chemical transformation of common chemical functionalities in natural products into chemical functionalities rarely found in nature. The resulting mixture showed antifungal activity against Candida albicans, whereas the starting extract did not show such activity. Bioguided fractionation led to the isolation of a previously undescribed active semisynthetic pyrazole. The result illustrates how biological activity can be generated by designed chemical diversification of a natural product mixture, and represents the proof of principle of an alternative strategy for producing natural product-like libraries from natural products libraries.

An unusual homoisoflavanone and a structurally-related dihydrochalcone from Polygonum ferrugineum (Polygonaceae)

The homoisoflavanone 5,7-dihydroxy-6-methoxy-3-(9-hydroxy-phenylmethyl)-chroman-4-one (1) and its structurally related 2',4',6'-trihydroxy-3'-methoxy-alpha-hydroxymethyl-beta-hydroxy-dihydrochalcone (2) along with the known pashanone (3), flavokawin B (4) and cardamonin or alpinetin chalcone (5) pinostrobin (6) and 5,8-dimethoxy-7-hydroxychroman-4-one (7) were isolated from dry leaves of Polygonum ferrugineum (Polygonaceae). To our knowledge, this is the first report of the isolation of a homoisoflavanone from the Polygonum genus and the Polygonaceae family, and could be an important chemotaxonomic finding. In addition, the pattern of substitution of this homoisoflavanone is different from others previously reported.

Enantiospecific Syntheses ofC(5)-Functionalized Precursors of Artemisinin Derivatives

Enantiomerically pure compounds as precursors for the synthesis of hydroxylated derivatives of artemisinin/arteether have been prepared from (+)-(S)-carvone and (+)-car-2-ene.

Isolation of antifungal saponins from Phytolacca tetramera, an Argentinean species in critic risk

The methanolic extract of the berries of Phytolacca tetramera, an Argentinean species submitted to a great anthropic impact, and therefore in critic risk of extinction, not previously studied, showed antifungal activity against opportunistic pathogenic fungi. Through fractionation of the extract followed by agar dilution assays, three monodesmosidic triterpenoid saponins have been isolated from the butanolic extract of P. tetramera. The structures were established as phytolaccosides: B [3-O-beta-D-xylopiranosyl-phytolaccagenin], E [3-O-beta-D-glucopyranosyl-(1-->4)-beta-D-xylopiranosyl-phytolaccagenin]. and F [3-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranosyl-(1-->2)-beta-D-xylopyranosyl-phytolaccagenic acid]. The three saponins belong to the olean-type triterpenoid saponins, with 28,30 dicarboxylic groups and an olefinic double bond on C-12. Phytolaccosides B and E but not phytolaccoside F, showed antifungal activities against a panel of human pathogenic opportunistic fungi. Phytolaccoside B was the most active compound and showed the broadest spectrum of action. The most sensitive fungus was Trichophyton mentagrophytes.

The cytochrome c gene from the green alga Chlamydomonas reinhardtii. Structure and expression in wild-type cells and in obligate photoautotrophic (dk) mutants

The expression of the Chlamydomonas reinhardtii cytochrome c gene was studied at the steady-state mRNA level. The inclusion of acetate under illumination produced a marked increase in cytochrome c transcripts. This effect was not affected by two inhibitors of mitochondrial energy metabolism. Three different obligate photoautotrophic mutants with defective mitochondria showed normal levels of induction, suggesting that utilization of acetate for respiration is not required for this process. Light, in the presence or absence of acetate, also promoted an increase in cytochrome c transcript levels. This effect could be abolished by treatment of the cells with an inhibitor of the photosynthetic electron transport chain, suggesting that light acts through photosynthesis to promote the induction. In addition, a genomic clone encompassing the Chlamydomonas cytochrome c gene has been isolated and analyzed. The gene contains three introns, two of which are located at positions similar to those in the rice and Arabidopsis cytochrome c genes, indicating the existence of an evolutionary link. It is concluded that the cytochrome c gene from C. reinhardtii is subject to metabolic regulation through a mechanism that responds to the intracellular level of either acetate or a compound derived from its metabolization through a pathway different from mitochondrial respiration.

Complex formation between D-lactobionate and bivalent metal ions. Studies in solution and in the solid state

The equilibrium reactions between deprotonated D-lactobionic acid (4-O-β-D-galactopyranosyl-D-gluconic acid) and cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and mercury(II) have been studied by potentiometric and spectrophotometric methods in aqueous solution. All measurements have been carried out at a temperature of 20.0 ± 0.1 °C and at an ionic strength of 0.100 M (NaNO3) with the corresponding stability constants calculated by applying computational methods. The interactions between the proposed cations with deprotonated D-lactobionic acid were compared with those corresponding to D-gluconic acid. Compounds of type: Co(C12H21O12)2•2H2O•C2H5OH, Ni(C12H21O12)2•2H2O•C2H5OH, Cu(C12H21O12)2•2H2O•C2H5OH, Zn(C12H21O12)2•2H2O•C2H5OH, and Cd(C12H21O12)2•2H2O•0.5C2H5OH have been isolated. These metal–sugar salts were characterized by elemental, thermogravimetric, and susceptibility analyses and FT-IR, UV–visible absorption, diffuse reflectance, and 13C NMR spectroscopies. Keywords: D-lactobionate, metal complexes, equilibrium constants, potentiometry, solid state studies.

Synthesis of Diastereoisomeric 2-Benzyl-1,2-diphenylindans

The diastereoisomeric 2-benzyl-1,2-diphenylindan-1-ols were prepared and subjected to deoxygenation reactions under a variety of conditions to obtain 2-benzyl-1,2-diphenylindan. The stereochemistry of these compounds has been characterized on the basis of chemical and spectroscopic evidence.