Phytochemistry Meets Geochemistry­Blumenol C Sulfate: A New Megastigmane Sulfate from Palicourea luxurians (Rubiaceae: Palicoureeae)

There is a previously neglected influence of geochemical conditions on plant phytochemistry. In particular, high concentrations of dissolved salts can affect their biosynthesis of natural products. Detoxification is most likely an important aspect for the plant, but additional natural products can also give it an expanded range of bioactivities. During the phytochemical analysis a Palicourea luxurians plant collected in a sulfate-rich environment (near the Río Sucio, Costa Rica) showed an interesting natural product in this regard. The structure of this compound was determined using spectroscopic and computational methods (NMR, MS, UV, IR, CD, optical rotation, quantum chemical calculations) and resulted in a megastigmane sulfate ester possessing a ß-ionone core structure, namely blumenol C sulfate (1, C13H22O5S). The levels of sulfur and sulfate ions in the leaves of the plant were determined using elemental analysis and compared to the corresponding levels in comparable plant leaves from a less sulfate-rich environments. The analyses show the leaves from which we isolated blumenol C sulfate (1) to contain 35% more sulfur and 80% more sulfate than the other samples. Antimicrobial and antioxidant activities of compound 1 were tested against Escherichia coli, E. coli ampR and Bacillus subtilis as well as measured using complementary in vitro FRAP and ATBS assays, respectively. These bioactivities are comparable to those determined for structurally related megastigmanes. The sulfur and sulfate content of the plant leaves from the sulfate-rich environment was significantly higher than that of the other plants. Against this background of salt stress, we discuss a possible biosynthesis of blumenol C sulfate (1). Furthermore, there appears to be no benefit for the plant in terms of extended bioactivities. Hence, the formation of blumenol C sulfate (1) probably primarily serves the plant detoxification process.

Controllable organosilane monolayer density of surface bonding using silatranes for thiol functionalization of silica particles for liquid chromatography and validation of microanalytical method for elemental composition determination.

The present work systematically investigates a new strategy for the functionalization of silica gel using alkyl silatrane chemistry instead of alkylsilanes for synthesis of chromatographic stationary phases. In this work, silica was chemically modified for further functionalization by a thiol-ene click reaction. Thus, 3-mercaptopropylsilatrane (MPS) was used which is capable to form self-assembled monolayers (SAM) on top of silanol surfaces in a controlled manner as previously shown for silicon wafers. The utility of this chemistry for stationary phase synthesis in liquid chromatography was not evaluated yet. Hence, silica surface modifications using MPS were studied in comparison to established 3-mercaptopropyltrimethoxysilane (MPTMS) chemistry. First, the employed elemental analysis method was validated and it showed excellent intra-day and inter-day precisions (typically less than 5% RSD). It could be shown that the reaction kinetics of MPS was roughly 35-times faster than with MPTMS. After 30 min reaction time with MPS, the thiol content reached 74% of the maximal coverage. Due to controlled chemistry with MPS, which does not lead to oligomeric siloxane network at the silica surface, the ligand coverage was lower. However, multiple silanization cycles with MPS led to a dense surface coverage (around 4 µmol m-2). 29Si cross polarization/magic angle spinning (CP/MAS) solid-state NMR revealed distinct T1/T2/T3 ratios for MPS and MPTMS materials with up to 80% T3 (indicative for trifunctional siloxane linkage) for MPS and around 20% T3 for MPTMS. This indicates a more homogeneous, thinner monolayer film of MPS on the silica surface, as compared to an irregular thick oligomeric siloxane network with MPTMS. Bonding of quinine carbamate as chiral selector afforded an efficient chiral stationary phase (CSP) for chromatographic enantiomer separation. Separation factors were comparable to MPTMS-bonded CSP, however, chromatographic efficiency was much better for the MPS-bonded CSP. H/u curves indicated a reduced mass transfer resistance by roughly factor 3 for MPS- compared to MPTMS-bonded CSP. This confirms better chromatographic performance of surfaces with homogeneous monolayer compared to network structures on the silica surface which suffer from poor stationary phase mass transfer.

Fragment-based Design of Zwitterionic, Strong Cation- and Weak Anion-Exchange Type Mixed-mode Liquid Chromatography Ligands and their Chromatographic Exploration.

The role of individual functional groups has been assessed with regard to surface charge and chromatographic retention. Coatings were prepared from various fragments of the chiral zwitterionic materials Chiralpak ZWIX(+) and ZWIX(-). The different chromatographic ligands allowed fine tuning of the surface charge. Chiralpak ZWIX phases showed strongly negative ζ-potentials over the entire pH-range. Zwitterionic congeners with quinuclidine and sulfonic acid moieties but lacking the quinolone ring in the ligand structure exhibited shifted ζ-potentials of around + 5 to 20 mV depending on the surrounding residues. Capillary electrophoretic mobilitiy measurements with the chromatographic ligands and molecular dynamics simulations were carried out to offer some explanation of these surface charge differences of the distinct zwitterionic stationary phases. The new mixed-mode phases were also chromatographically characterized by simple RP and HILIC tests. The results allowed their positioning within a large variety of different commercially available RP, HILIC and mixed-mode phases, which were evaluated as well, by multivariate data processing using principal component analysis. The new mixed-mode phases overall exhibit reasonable hydrophilicity-lipophilicity balance and enable retention of ionic compounds by additional ionic interactions through weak anion-exchange (WAX-type), strong cation-exchange (SCX-type) or both (RP/ZWIX-type). Hence, the new RP/ZWIX phases can be flexible tools for selectivity tuning in RP and HILIC separations.

Waste-Derived Low-Cost Mycelium Nanopapers with Tunable Mechanical and Surface Properties.

Mycelium, the vegetative growth of filamentous fungi, has attracted increasing commercial and academic interest in recent years because of its ability to upcycle agricultural and industrial wastes into low-cost, sustainable composite materials. However, mycelium composites typically exhibit foam-like mechanical properties, primarily originating from their weak organic filler constituents. Fungal growth can be alternatively utilized as a low-cost method for on-demand generation of natural nanofibrils, such as chitin and chitosan, which can be grown and isolated from liquid wastes and byproducts in the form of fungal microfilaments. This study characterized polymer extracts and nanopapers produced from a common mushroom reference and various species of fungal mycelium grown on sugarcane byproduct molasses. Polymer yields of ∼10-26% were achieved, which are comparable to those of crustacean-derived chitin, and the nanopapers produced exhibited much higher tensile strengths than the existing mycelium materials, with values of up to ∼25 MPa (mycelium) and ∼98 MPa (mushroom), in addition to useful hydrophobic surface properties resulting from the presence of organic lipid residues in the nanopapers. HCl or H2O2 treatments were used to remove these impurities facilitating tuning of mechanical, thermal, and surface properties of the nanopapers produced. This potentially enables their use in a wide range of applications including coatings, membranes, packaging, and paper.