Robert B. Bates

Structure and Characterization of Flavolipids, a Novel Class of Biosurfactants Produced by Flavobacterium sp. Strain MTN11

ABSTRACT Herein we report the structure and selected properties of a new class of biosurfactants that we have named the flavolipids. The flavolipids exhibit a unique polar moiety that features citric acid and two cadaverine molecules. Flavolipids were produced by a soil isolate, Flavobacterium sp. strain MTN11 (accession number AY162137 ), during growth in mineral salts medium, with 2% glucose as the sole carbon and energy source. MTN11 produced a mixture of at least 37 flavolipids ranging from 584 to 686 in molecular weight (MW). The structure of the major component (23%; MW = 668) was determined to be 4-[[5-(7-methyl-(E)-2-octenoylhydroxyamino)pentyl]amino]-2-[2-[[5-(7-methyl-(E)-2-octenoylhydroxyamino)pentyl]amino]-2-oxoethyl]-2-hydroxy-4-oxobutanoic acid. The partially purified flavolipid mixture isolated from strain MTN11 exhibited a critical micelle concentration of 300 mg/liter and reduced surface tension to 26.0 mN/m, indicating strong surfactant activity. The flavolipid mixture was a strong and stable emulsifier even at concentrations as low as 19 mg/liter. It was also an effective solubilizing agent, and in a biodegradation study, it enhanced hexadecane mineralization by two isolates, MTN11 (100-fold) and Pseudomonas aeruginosa ATCC 9027 (2.5-fold), over an 8-day period. The flavolipid-cadmium stability constant was measured to be 3.61, which is comparable to that for organic ligands such as oxalic acid and acetic acid. In summary, the flavolipids represent a new class of biosurfactants that have potential for use in a variety of biotechnological and industrial applications.

Stability studies of tetracycline in methanol solution.

The stability of tetracycline in methanol solution was investigated by UV-visible spectroscopy, HPLC and TLC methods. After dissolution in methanol, tetracycline decomposed rapidly under the influence of light and atmospheric oxygen, forming more than fourteen different degradation products. None of the previously reported degradation products, such as the epi- and anhydro-compounds, were detected as the final degradation products. The molecular structures for eight of the compounds were suggested by their product-ion mass spectra. A degradation sequence was proposed for the reactions of tetracycline with methanol. A new HPLC-MS mobile phase was developed, which solved the clogging problem at the interface between the HPLC and MS chamber and enabled a high separation efficiency.

Grindelane diterpenoids from Grindelia campórum and Chrysothamnus paniculatus

Abstract The structures of nine grindelic acid related diterpenes isolated as methyl esters from Grindelia camporum and Chrysothamnus paniculatus , were elucidated based on their spectral properties.

Detoxification of the phytoalexins maackiain and medicarpin by fungal pathogens of alfalfa

Abstract Nine fungal pathogens of alfalfa ( Medicago sativa ) (lucerne) were assayed for their ability to metabolize the pterocarpanoid phytoalexins (−)maackiain and (−)medicarpin. All of the alfalfa fungal isolates were able to metabolize both (−)maackiain and (−)medicarpin. Six different initial reaction products were observed, and often a single isolate produced multiple metabolic products. All the products have been previously described, except for those produced by Cercospora medicaginis . This fungus hydroxylated the pterocarpans at the 1a carbon to form a 1a[ R ]OH-dienone, in which the hydroxyl group is trans to the bridgehead protons, and is the 1a epimer of the previously described cis form of the compound. (−)Maackiain and both of the 1a hydroxylated epimers were tested for toxicity on isolates of Nectria haematococca mating population I and Saccharomyces cerevisiae that do not degrade maackiain or its 1aOH-dienone products. Both epimers were less toxic than maackiain, and the trans epimer was less toxic than the cis form.

Characterization of Anti — HIV Lignans

Abstract Fractions from Larrea tridentata with anti-HIV-1 activity (specifically, inhibition of HIV Tat transactivation) were analyzed by GC/MS and NMR and found to contain lignans 1a-i and 2a-d . Assay-guided purification by countercurrent chromatography established 1g (mal.4) to be especially active. Compounds 1b-f, h, i and 2d are new.

A Phytochemical investigation of Alchornea latifolia

A phytochemical investigation of the chloroform leaf extract of Alchornea latifolia has been undertaken. Along with the triterpenoids taraxerone, friedelin, epifriedelinol, and taraxerol, the plant also contains seco-3,4-friedelin (dihydroputranjivic acid) (1) and seco-3,4-taraxerone (2). These A-ring-opened triterpenoids show in vitro cytotoxic activity against Hep-G2 and A-431 human cancer cell lines and are potent inhibitors of topoisomerase II.

Isolation of lignans from Schisandra chinensis with anti-proliferative activity in human colorectal carcinoma: Structure-activity relationships.

Separate benzocyclooctadiene lignans were isolated from the berries of Schisandra chinensis in milligram quantities on analytical reverse phase (RP) HPLC by an automated repeat-injection method and shown to have anti-proliferative activity against human colorectal cancer cells. Structures of the compounds were determined by a combination of NMR and mass spectrometry. Stereospecific NMR assignments for gomisin-N and deoxyschisandrin, gave more complete and accurate data than previously reported, based on 600MHz 2D HSQC, DQF-COSY and HMBC data. Comparison of coupling constants and HMBC crosspeak intensities with calculated and X-ray crystal structures confirmed their stereochemistry and conformation. Analysis of structure-activity relationships revealed the importance of key structural determinants. The S-biphenyl configuration of gomisin N, the most active lignan, correlated with increased anti-proliferative activity, while the presence of a hydroxyl group at the C7 position reduced or abolished this activity. Increased activity was also observed when a methylenedioxy group was present between C12 and C13. The percent yield of the most active compounds relative to the starting plant materials was 0.0156% for deoxyschisandrin and 0.0173% for gomisin N. The results of these studies indicate that automated repeat-injection method of analytical HPLC may provide a superior alternative to the standard semi-preparative HPLC techniques for separation of complex mixtures.

Structure and reactions of a cyanogenetic lipid from Cordia verbenacea DC. seed oil

Abstract Cordia verbenacea DC. (Boraginaceae) seed oil consists of a mixture of cyanogenetic, nonglycerol diesters (35%) and ordinary triglycerides. The nitrogen-containing esters are composed of two ordinary fatty acid moieties (predominantly C 20 ) esterified with a five-carbon dihydroxynitrile containing a terminal methylene grouping. All attempts to isolate this diol in an unesterified form resulted in mixtures of unstable products. The diesters form hydrogen cyanide on treatment with base and also yield formaldehyde upon mild alkaline oxidation. Hydrogen uptake is erratic, and varying degrees of hydrogenolysis with formation of monoesters occur when platinum or palladium is used as catalyst. Hydrolysis of the diesters with barium hydroxide gives a mixture of products which appear to be unsaturated hydroxy lactams. γ-Lactones with one acyl group attached are generated by refluxing the diesters with glacial acetic acid containing sulfuric acid as a catalyst.

Dolastatin 11 Connects Two Long-pitch Strands in F-actin to Stabilize Microfilaments

Dolastatin 11, a drug isolated from the Indian Ocean sea hare Dolabella auricularia, arrests cytokinesis in vivo and increases the amount of F-actin to stabilize F-actin in vitro, like phalloidin and jasplakinolide. However, according to the previous biochemical study, the binding of dolastatin 11 to F-actin does not compete with that of phalloidin, suggesting that the binding sites are different. To understand the mechanism of F-actin stabilization by dolastatin 11, we determined the position of bound dolastatin 11 in F-actin using the X-ray fiber diffraction from oriented filament sols. Our analysis shows that the position of dolastatin 11 is clearly different from that of phalloidin. However, these bound drugs are present in the gap between the two long-pitch F-actin strands in a similar way. The result suggests that the connection between the two long-pitch F-actin strands might be a key for the control of F-actin stabilization.

Cardenolides and a lignan from Asclepias subulata

Abstract Four new glycosides (three cardenolides and a lignan), nine previously reported cardenolide glycosides and a known triterpenoid were isolated from the ethyl acetate extract of the aerial parts of Asclepias subulata . The elucidation of the structures and stereochemistry of the new glycosides has been accomplished using mainly 1 H and 13 C NMR and mass (EI and FAB) spectral data of their acetyl derivatives and comparison of these data with those of known glycosides from the same plant as well as from other plants. The new compounds were identified as 16α-hydroxycalactin, 3β-(β- D -glucopyranosyloxy)-19-car coroglaucigenin 3β- D -glucoside and 4-(β- D -glucopyranosyloxy)-larciresinol.