Antibacterial and antifungal activity of sulfur-containing compounds from Petiveria alliacea

Abstract A total of 18 organosulfur compounds originating from Petiveria alliacea L. roots have been tested for their antibacterial and antifungal activities. These represent compounds occurring in fresh homogenates as well as those present in various macerates, extracts and other preparations made from Petiveria alliacea. Of the compounds assayed, the thiosulfinates, trisulfides and benzylsulfinic acid were observed to be the most active, with the benzyl-containing thiosulfinates exhibiting the broadest spectrum of antimicrobial activity. The effect of plant sample preparation conditions on the antimicrobial activity of the extract is discussed

The amino acid precursors and odor formation in society garlic (Tulbaghia violacea Harv).

Abstract Identification and isolation of (R S R C )-S-(methylthiomethyl)cysteine-4-oxide from rhizomes of Tulbaghia violacea Harv. is reported. The structure and absolute configuration of the amino acid have been determined by NMR, MALDI-HRMS, IR, and CD spectroscopy. Its content varied in different parts of the plant (rhizomes, leaves, and stems) between 0.12 and 0.24 mg g À1 fr. wt, being almost equal in the stems and rhizomes. In addition, S-methyl-and S-ethylcysteine derivatives have been detected in minute amounts (< 3 mg g À1 fr. wt) in all parts of the plant. The enzymatic cleavage of the amino acid and subsequent odor formation are discussed. 2,4,5,7-Tetrathiaoctane-4-oxide, the primary breakdown product, has been detected and isolated for the first time.

Inhibition of Biofilm Formation, Quorum Sensing and Infection in Pseudomonas aeruginosa by Natural Products-Inspired Organosulfur Compounds

Using a microplate-based screening assay, the effects on Pseudomonas aeruginosa PAO1 biofilm formation of several S-substituted cysteine sulfoxides and their corresponding disulfide derivatives were evaluated. From our library of compounds, S-phenyl-L-cysteine sulfoxide and its breakdown product, diphenyl disulfide, significantly reduced the amount of biofilm formation by P. aeruginosa at levels equivalent to the active concentration of 4-nitropyridine-N-oxide (NPO) (1 mM). Unlike NPO, which is an established inhibitor of bacterial biofilms, our active compounds did not reduce planktonic cell growth and only affected biofilm formation. When used in a Drosophila-based infection model, both S-phenyl-L-cysteine sulfoxide and diphenyl disulfide significantly reduced the P. aeruginosa recovered 18 h post infection (relative to the control), and were non-lethal to the fly hosts. The possibility that the observed biofilm inhibitory effects were related to quorum sensing inhibition (QSI) was investigated using Escherichia coli-based reporters expressing P. aeruginosa lasR or rhIR response proteins, as well as an endogenous P. aeruginosa reporter from the lasI/lasR QS system. Inhibition of quorum sensing by S-phenyl-L-cysteine sulfoxide was observed in all of the reporter systems tested, whereas diphenyl disulfide did not exhibit QSI in either of the E. coli reporters, and showed very limited inhibition in the P. aeruginosa reporter. Since both compounds inhibit biofilm formation but do not show similar QSI activity, it is concluded that they may be functioning by different pathways. The hypothesis that biofilm inhibition by the two active compounds discovered in this work occurs through QSI is discussed

Pushing the temporal resolution in absorption and Zernike phase contrast nanotomography: Enabling fast in situ experiments

Hard X-ray nanotomography enables 3D investigations of a wide range of samples with high resolution (<100 nm) with both synchrotron-based and laboratory-based setups. However, the advantage of synchrotron-based setups is the high flux, enabling time resolution, which cannot be achieved at laboratory sources. Here, the nanotomography setup at the imaging beamline P05 at PETRA III is presented, which offers high time resolution not only in absorption but for the first time also in Zernike phase contrast. Two test samples are used to evaluate the image quality in both contrast modalities based on the quantitative analysis of contrast-to-noise ratio (CNR) and spatial resolution. High-quality scans can be recorded in 15 min and fast scans down to 3 min are also possible without significant loss of image quality. At scan times well below 3 min, the CNR values decrease significantly and classical image-filtering techniques reach their limitation. A machine-learning approach shows promising results, enabling acquisition of a full tomography in only 6 s. Overall, the transmission X-ray microscopy instrument offers high temporal resolution in absorption and Zernike phase contrast, enabling in situ experiments at the beamline

Electron population dynamics in resonant non-linear x-ray absorption in nickel at a free-electron laser

Free-electron lasers provide bright, ultrashort, and monochromatic x-ray pulses, enabling novel spectroscopic measurements not only with femtosecond temporal resolution: The high fluence of their x-ray pulses can also easily enter the regime of the non-linear x-ray–matter interaction. Entering this regime necessitates a rigorous analysis and reliable prediction of the relevant non-linear processes for future experiment designs. Here, we show non-linear changes in the L3-edge absorption of metallic nickel thin films, measured with fluences up to 60 J/cm2. We present a simple but predictive rate model that quantitatively describes spectral changes based on the evolution of electronic populations within the pulse duration. Despite its simplicity, the model reaches good agreement with experimental results over more than three orders of magnitude in fluence, while providing a straightforward understanding of the interplay of physical processes driving the non-linear changes. Our findings provide important insights for the design and evaluation of future high-fluence free-electron laser experiments and contribute to the understanding of non-linear electron dynamics in x-ray absorption processes in solids at the femtosecond timescale

Cysteine sulfoxide derivatives in Petiveria alliacea

Abstract Two diastereomers of S-benzyl-l-cysteine sulfoxide have been isolated from fresh roots of Petiveria alliacea. Their structures and absolute configurations have been determined by NMR, MALDI-HRMS, IR and CD spectroscopy and confirmed by comparison with authentic compounds. Both the R S and S S diastereomers of the sulfoxide are present in all parts of the plant (root, stem, and leaves) with the latter diastereomer being predominant. Their total content greatly varied in different parts of the plant between 0.07 and 2.97 mg g À1 fr. wt, being by far the highest in the root. S-Benzylcysteine has also been detected in trace amounts (&lt; 10 mg g À1 fr. wt) in all parts of the plant. This represents the first report of the presence of S-benzylcysteine derivatives in nature.

Discovery and Characterization of a Novel Lachrymatory Factor Synthase in Petiveria alliacea and Its Influence on Alliinase-Mediated Formation of Biologically Active Organosulfur Compounds1[W][OA]

A novel lachrymatory factor synthase (LFS) was isolated and purified from the roots of the Amazonian medicinal plant Petiveria alliacea. The enzyme is a heterotetrameric glycoprotein comprised of two α-subunits (68.8 kD each), one γ-subunit (22.5 kD), and one δ-subunit (11.9 kD). The two α-subunits are glycosylated and connected by a disulfide bridge. The LFS has an isoelectric point of 5.2. It catalyzes the formation of a sulfine lachrymator, (Z)-phenylmethanethial S-oxide, only in the presence of P. alliacea alliinase and its natural substrate, S-benzyl-l-cysteine sulfoxide (petiveriin). Depending on its concentration relative to that of P. alliacea alliinase, the LFS sequesters, to varying degrees, the sulfenic acid intermediate formed by alliinase-mediated breakdown of petiveriin. At LFS:alliinase of 5:1, LFS sequesters all of the sulfenic acid formed by alliinase action on petiveriin, and converts it entirely to (Z)-phenylmethanethial S-oxide. However, starting at LFS:alliinase of 5:2, the LFS is unable to sequester all of the sulfenic acid produced by the alliinase, with the result that sulfenic acid that escapes the action of the LFS condenses with loss of water to form S-benzyl phenylmethanethiosulfinate (petivericin). The results show that the LFS and alliinase function in tandem, with the alliinase furnishing the sulfenic acid substrate on which the LFS acts. The results also show that the LFS modulates the formation of biologically active thiosulfinates that are downstream of the alliinase in a manner dependent upon the relative concentrations of the LFS and the alliinase. These observations suggest that manipulation of LFS-to-alliinase ratios in plants displaying this system may provide a means by which to rationally modify organosulfur small molecule profiles to obtain desired flavor and/or odor signatures, or increase the presence of desirable biologically active small molecules