Functional properties of nisin–carbohydrate conjugates formed by radiation induced Maillard reaction

Nisin–carbohydrate conjugates were prepared by irradiating nisin either with glucose or dextran. Increase in browning and formation of intermediate products was observed with a concomitant decrease in free amino and reducing sugar groups indicating occurrence of the Maillard reaction catalyzed by irradiation. Nisin–carbohydrate conjugates showed a broad spectrum antibacterial activity against Gram negative bacteria (Escherichia coli, Pseudomonas fluorescence) as well as Gram positive bacteria (Staphylococcus aureus, Bacillus cereus). Results of antioxidant assays, including that of DPPH radical-scavenging activity and reducing power, showed that the nisin–dextran conjugates possessed better antioxidant potential than nisin–glucose conjugate. These results suggested that it was possible to enhance the functional properties of nisin by preparing radiation induced conjugates suitable for application in food industry.     

Synthesis of resorcin[4]arene cavitands by ring-closing metathesis

The synthesis and X-ray crystal structures of the first resorcin[4]arene cavitands by ring-closing metathesis reaction are described.     

Structural Characterization of a Benzoxazinophenoxazine Formed as a By‐Product During the Synthesis of a 3‐Amino‐N,N‐dimethylsalicylamide

Several highly colored by‐products were observed chromatographically during the synthesis of 3‐amino‐N,N‐dimethylsalicylamide. One of these, an oxidative dimerization products, bis‐(N,N‐dimethylcarboxamido)‐aminophenoxazinone, was previously isolated and characterized. A tris‐(N,N‐dimethylcarboxamido)‐benzoxazino[3,2‐b]phenoxazine, presumably a higher oxidation or further reaction product of the previously isolated and characterized 2‐amino‐3 H ‐phenoxazin‐3‐one, has also been isolated and characterized by mass spectrometry and multinuclear NMR methods. We now wish to communicate the results of that structure characterization effort.     

Synthesis of glycolipid analogs via highly regioselective macrolactonization catalyzed by lipase

Highly regioselective lipase catalyzed macrolactonization has been used in synthesizing first feedstock based glycolipid analogs. These macrolides containing common disaccharides maltose (4-O-α-d-glucopyranosyl-β-d-glucose) and melibiose (6-O-α-d-galactopyranosyl-β-d-glucose) were synthesized by employing chemoenzymatic methodologies. Maltose and Melibiose were coupled with methyl 15-hydroxy pentadecanoate and then subjected to a highly regioselective macrolactonization at the C-6″ position using Candida antarctica lipase-B to yield the desired products.     

Structural Characterization of a Phenoxazine Analog Formed as a By‐product of the Synthesis of a 3‐Amino‐N,N‐dimethylsalicylamide

A highly colored impurity formed at low levels during the preparation of 3‐amino N,N‐dimethyl salicylamide was isolated and identified as 2‐amino‐N,N,N′,N′‐tetramethyl‐3‐oxo‐3H‐phenoxazin‐4,6‐dicarboxamide using mass spectrometry and two‐dimensional NMR methods that included long‐range ¹H‐¹⁵N heteronuclear chemical shift correlation data to assemble the proton‐deficient “right‐half” of the 2‐aminophenoxazin‐3‐one nucleus. The structure was independently confirmed using computer‐assisted structure elucidation methods and by synthesis.