Total synthesis of pinellic acid, a potent oral adjuvant for nasal influenza vaccine. Determination of the relative and absolute configuration

Identification of inhibitors of pinellic acid generation in whole wheat bread

Bitterness is a common aversive flavor attribute of foods associated with low consumer acceptance. Untargeted LC-MS flavoromic profiling was utilized to identify endogenous compounds that influence the generation of the bitter compound 9,12,13-trihydroxy-trans-10-octadecenoic acid (pinellic acid) during bread making. A diverse sample set of wheat germplasm was chemically profiled. The corresponding pinellic acid concentrations after dough formation were modeled by orthogonal partial least squares (OPLS) with good fit (R²Y = 0.8) and predictive ability (Q² = 0.6). The most predictive feature (negatively correlated), postulated to interfere with the biosynthetic pathway, was identified as schaftoside, an apigenin di-C-glycoside. Recombination experiments involving the addition of schaftoside to flour prior to breadmaking resulted in a 26% decrease in pinellic acid formation and significantly lower perceived bitterness intensity in whole wheat bread. This work provides novel understanding of bitter generation pathways in wheat products and new strategies to improve flavor profiles and consumer acceptability.

Challenges in the configuration assignment of natural products. A case-selective perspective

An overview by a case study approach on the currently available methods for the configurational analysis of natural products.

Chemical profiling (HPLC-NMR & HPLC-MS), isolation, and identification of bioactive meroditerpenoids from the southern Australian marine brown alga Sargassum paradoxum

A phytochemical investigation of a southern Australian marine brown alga, Sargassum paradoxum, resulted in the isolation and identification of four new (5, 9, 10, and 15) and nine previously reported (1, 2, 6-8, and 11-14) bioactive meroditerpenoids. HPLC-NMR and HPLC-MS were central to the identification of a new unstable compound, sargahydroquinal (9), and pivotal in the deconvolution of eight (1, 2, 5-7, and 10-12) other meroditerpenoids. In particular, the complete characterization and identification of the two main constituents (1 and 2) in the crude dichloromethane extract was achieved using stop-flow HPLC-NMR and HPLC-MS. This study resulted in the first acquisition of gHMBCAD NMR spectra in the stop-flow HPLC-NMR mode for a system solely equipped with a 60 μL HPLC-NMR flow cell without the use of a cold probe, microcoil, or any pre-concentration.

Advantages of electronic circular dichroism detection for the stereochemical analysis and characterization of drugs and natural products by liquid chromatography

The need for analytical methods for the determination of the enantiomeric excess of chiral compounds increased significantly in the last decades, and enantioselective separation techniques resulted particularly efficient to this purpose. Moreover, when detection systems based on chiroptical properties (optical rotation or circular dichroism) are employed in high-performance liquid chromatography (HPLC), the stereochemistry of a chiral analyte can be fully determined. Indeed, the coupling of HPLC with chiroptical detection systems allows the simultaneous assessment of the absolute configuration of stereoisomers and the evaluation of the enantiomeric/diastereomeric excess of samples. These features are particularly important in the study of drugs and natural products provided with biological activity, because the assignment of their absolute stereochemistry is essential to establish reliable structure-activity relationships. The following review aims to discuss the analytical advantages arising from the employment of electronic circular dichroism (ECD) detection systems in stereochemical analysis by HPLC upon chiral and non-chiral stationary phases and their use for the stereochemical characterization of chiral drugs and natural compounds. The different methods for the correlation between absolute stereochemistry and chiroptical properties are critically discussed. Relevant HPLC applications of ECD detection systems are then reported, and their analytical advantages are highlighted. For instance, the importance of the concentration-independent anisotropy factor (g-factor; g=Δɛ/ɛ) for the determination of the stereoisomeric composition of samples upon non-chiral stationary phases is underlined, since its sensitivity makes ECD detection very well suited for the enantioselective analysis of large libraries of chiral compounds in relatively short times.

Total syntheses of schulzeines B and C

Schulzeines B (2) and C (3) were synthesized by a convergent strategy using epimeric tricyclic lactam building blocks, 4 and 5, and the C28 fatty acid side chain 6. Syntheses of tricyclic lactams (4/5) were achieved by Bischler-Napieralski reaction. Sharpless asymmetric dihydroxylation and BINAL-H-mediated asymmetric reduction of an enone was employed to prepare the key fatty acid side chain 6. The spectral as well as analytical data of 2 and 3 were in good agreement with the reported data for the natural products, thus confirming their assigned structures.

Phytochemical constituents from Salsola tetrandra

The new norisoprenoid 3beta-hydroxy-5alpha,6alpha-epoxy-beta-ionone-2alpha-O-beta-d-glucopyranoside (1) and the long-chain hydroxy fatty acids 9,12,13-trihydroxyoctadeca-10(E),15(Z)-dienoic acid (2) and 9,12,13-trihydroxyoctadeca-10(E)-dienoic acid (3) were isolated from Salsola tetrandra aerial parts, together with 3,4,5-trimethoxyphenyl-beta-d-glucopyranoside (4), 9-hydroxylinaloyl glucoside (5), taxiphyllin (6), trans-N-feruloyltyramine (7), and S-(-)-trans-N-feruloyloctopamine (8). Their structures were elucidated by extensive spectroscopic analysis and chemical methods. Compounds 6 and 8 displayed mild antibacterial activity against Staphylococcus aureus, whereas compound 6 showed the highest activity in the Artemia salina bioassay.

Encapsulation of Neutral Guests by Tri(ethylene oxide)-pyrrole-Terminated Dendrimer Hosts in Water

[reaction: see text] This work focuses on the synthesis and guest hosting capabilities of novel, water-soluble tri(ethylene oxide)-pyrrole-functionalized poly(propylene imine), PPI, dendrimers (DAB-TEOPy(n)). The high-generation DAB-TEOPy(n) (n = 32 and 64) possesses the ability to encapsulate hydrophobic guest molecules, such as Nile Red, in aqueous media.

Total synthesis and adjuvant activity of all stereoisomers of pinellic acid

Pinellic acid is a novel and potentially useful oral adjuvant when used in conjunction with intranasal inoculation of influenza HA vaccines. All stereoisomers of pinellic acid have been synthesized via regioselective asymmetric dihydroxylation, regioselective inversion, and stereoselective reduction, and their adjuvant activities were characterized. Among this series of isomers, 9S, 12S, 13S compound has the most potent adjuvant activity. Structure-activity relationships are discussed.