Comparative metabolic profiling of <i>Costus speciosus</i> leaves and rhizomes using NMR, GC-MS and UPLC/ESI-MS/MS

<p><i>Costus speciosus</i> had been used in oriental systems of medicines, to treat diverse ailments. The present study was focused on NMR, GC-MS and UPLC/ESI-MS/MS-based metabolic profiling of <i>C. speciosus</i>. This metabolic study resulted in the identification of 91 and quantification of 69 metabolites. Caffeic acid derivatives previously unreported in <i>C. speciosus</i> were also identified. High quantity of steroidal saponins namely methyl protogracillin (297.97 ± 0.07 mg/g dried wt.) and dioscin (158.72 ± 0.27 mg/g dried wt.) were observed in butanol fraction of rhizomes. Health care metabolites including caffeic acid (37.88 ± 0.04 mg/g dried wt.) and trehalose (75.12 ± 0.08 mg/g dried wt.) were also detected in ethyl acetate and aqueous fractions of rhizomes, respectively. Metabolites of nutraceutical and biological significance including eremanthine (5.14 ± 0.68%, peak area), tocopherols (~22%), sterols (~25%) were also identified from hexane fractions of rhizomes and leaves using GC-MS. The analytical techniques used had successfully differentiated metabolites composition among leaves and rhizomes.</p

Structure and Binding Properties to Blood Co-Factors of the Least Sulfated Galactan Found in the Cell Wall of the Red Alga <i>Botryocladia occidentalis</i>

Three different populations of sulfated polysaccharides can be found in the cell wall of the red alga Botryocladia occidentalis. In a previous work, the structures of the two more sulfated polysaccharides were revised. In this work, NMR-based structural analysis was performed on the least sulfated polysaccharide and its chemically modified derivatives. Results have revealed the presence of both 4-linked α- and 3-linked β-galactose units having the following chemical features: more than half of the total galactose units are not sulfated, the α-units occur primarily as 3,6-anhydrogalactose units either 2-O-methylated or 2-O-sulfated, and the β-galactose units can be 4-O-sulfated or 2,4-O-disulfated. SPR-based results indicated weaker binding of the least sulfated galactan to thrombin, factor Xa, and antithrombin, but stronger binding to heparin cofactor II than unfractionated heparin. This report together with our previous publication completes the structural characterization of the three polysaccharides found in the cell wall of the red alga B. occidentalis and correlates the impact of their composing chemical groups with the levels of interaction with the blood co-factors

Sequential Pd(0)/Fe(III) Catalyzed Azide–Isocyanide Coupling/Cyclization Reaction: One-Pot Synthesis of Aminotetrazoles

A rapid and efficient synthesis of aminotetrazole from aryl azides, isocyanides, and TMSN₃ is developed. The reaction is promoted by sequential Pd(0)/Fe­(III) catalysis. The reaction sequence utilizes the Pd-catalyzed azide–isocyanide denitrogenative coupling reaction to generate unsymmetric carbodiimide <i>in situ</i>, which reacts with TMSN₃ in the presence of FeCl₃ in a single pot. The methodology has distinct advantages over traditional synthetic approaches where toxic Hg and Pb salts are employed at stoichiometric scale

Sequential Pd(0)/Fe(III) Catalyzed Azide–Isocyanide Coupling/Cyclization Reaction: One-Pot Synthesis of Aminotetrazoles

A rapid and efficient synthesis of aminotetrazole from aryl azides, isocyanides, and TMSN₃ is developed. The reaction is promoted by sequential Pd(0)/Fe­(III) catalysis. The reaction sequence utilizes the Pd-catalyzed azide–isocyanide denitrogenative coupling reaction to generate unsymmetric carbodiimide <i>in situ</i>, which reacts with TMSN₃ in the presence of FeCl₃ in a single pot. The methodology has distinct advantages over traditional synthetic approaches where toxic Hg and Pb salts are employed at stoichiometric scale

Ruthenium Catalyzed Intramolecular C–S Coupling Reactions: Synthetic Scope and Mechanistic Insight

A ruthenium catalyzed intramolecular C–S coupling reaction of <i>N</i>-arylthioureas for the synthesis of 2-aminobenzo­thiazoles has been developed. Kinetic, isotope labeling, and computational studies reveal the involvement of an electrophilic ruthenation pathway instead of a direct C–H activation. Stereoelectronic effect of meta-substituents on the <i>N</i>-arylthiourea dictates the final regioselective outcome of the reaction