Synthese von enantiomerenreinen Violaxanthinen und verwandten Verbindungen

Concise and Practical Total Synthesis of (+)-Abscisic Acid

(+)-Abscisic acid 1 was obtained in a concise total synthesis from ethyl 2,6,6-trimethyl-4-oxocyclohex-2-ene-1-carboxylate (2) with 41% overall yield in seven steps. A hydroxyl group was stereoselectively introduced by Sharpless asymmetric epoxidation; then, the side chain was appended with dimethyl 2-(propan-2-ylidene)malonate (7); subsequently, selective decarboxylation of diacid 8 established the Z-configuration of the conjugated acid 1.

Enantioselective synthesis of (−)-phaseic acid

A short, enantioselective synthesis of a newly identified ABA receptor agonist (−)-phaseic acid is described.

Spectrophotometric Analysis of Pigments: A Critical Assessment of a High-Throughput Method for Analysis of Algal Pigment Mixtures by Spectral Deconvolution

The Gauss-peak spectra (GPS) method represents individual pigment spectra as weighted sums of Gaussian functions, and uses these to model absorbance spectra of phytoplankton pigment mixtures. We here present several improvements for this type of methodology, including adaptation to plate reader technology and efficient model fitting by open source software. We use a one-step modeling of both pigment absorption and background attenuation with non-negative least squares, following a one-time instrument-specific calibration. The fitted background is shown to be higher than a solvent blank, with features reflecting contributions from both scatter and non-pigment absorption. We assessed pigment aliasing due to absorption spectra similarity by Monte Carlo simulation, and used this information to select a robust set of identifiable pigments that are also expected to be common in natural samples. To test the method’s performance, we analyzed absorbance spectra of pigment extracts from sediment cores, 75 natural lake samples, and four phytoplankton cultures, and compared the estimated pigment concentrations with concentrations obtained using high performance liquid chromatography (HPLC). The deviance between observed and fitted spectra was generally very low, indicating that measured spectra could successfully be reconstructed as weighted sums of pigment and background components. Concentrations of total chlorophylls and total carotenoids could accurately be estimated for both sediment and lake samples, but individual pigment concentrations (especially carotenoids) proved difficult to resolve due to similarity between their absorbance spectra. In general, our modified-GPS method provides an improvement of the GPS method that is a fast, inexpensive, and high-throughput alternative for screening of pigment composition in samples of phytoplankton material.

Wilsonols A-L, megastigmane sesquiterpenoids from the leaves of Cinnamomum wilsonii

Twelve new megastigmane sesquiterpenoids, wilsonols A-L (1-12), were isolated from the leaves of Cinnamomum wilsonii, along with seven known analogues (13-19). The structures of compounds 1-12 were established by spectroscopic analyses. The absolute configurations of 1-5 were determined by single-crystal X-ray diffraction analysis with Cu Kα irradiation, and the absolute configurations of 6-12 were determined by the modified Mosher's method. Compounds 1-9 and 13-19 were evaluated for in vitro cytotoxicity against five human cancer cell lines, HL-60, SMMC-7721, A-549, MCF-7, and SW-480, and compared against the Beas-2B immortalized (noncancerous) human bronchial epithelial cell line. Compound 13 exhibited IC50 values ranging from 2.5 to 12 μM and selectivity indices of >10 against SMMC-7721, A-549, and MCF-7 cell lines. Selected compounds were evaluated for in vitro immunomodulatory activity.

Anti-inflammatory effects of violaxanthin isolated from microalga Chlorella ellipsoidea in RAW 264.7 macrophages

Violaxanthin is a major carotenoid of microalgae Chlorella ellipsoidea and is also found in dark-green leafy vegetables, such as spinach. In this study, the anti-inflammatory effect of violaxanthin isolated from C. ellipsoidea was examined using lipopolysaccharide (LPS)-stimulated RAW 264.7 mouse macrophage cells. In addition, the anti-inflammatory activity and mechanism of action of purified violaxanthin was assessed using various assays, such as quantitative real-time polymerase chain reaction (PCR), Western blotting, and electrophoretic-mobility shift assay (EMSA). The results of this combined analysis revealed that violaxanthin significantly inhibited nitric oxide (NO) and the prostaglandin E₂ (PGE₂). Interestingly, violaxanthin effectively inhibited LPS-mediated nuclear factor-κB (NF-κB) p65 subunit translocation into the nucleus, suggesting that the violaxanthin anti-inflammatory activity may be based on inhibition of the NF-κB pathways. In conclusion, violaxanthin of C. ellipsoidea holds promise for use as a potential anti-inflammatory agent for either therapeutic or functional adjuvant purposes.

Structure of three new carotenoids with a 3-methoxy-5-keto-5,6-seco-4,6-cyclo-beta end group from the seeds of Pittosporum tobira

Three new carotenoids with a 3-methoxy-5-keto-5,6-seco-4,6-cyclo-beta end group (1-3) have been isolated from the seeds of Pittosporum tobira. Their structures were elucidated by detailed analyses of nuclear magnetic resonance and UV data.