Production of a low calorie mandarin juice by enzymatic conversion of constituent sugars to oligosaccharides and prevention of insoluble glucan formation.

Over 99% of sucrose in mandarin juice (57.1 g/l in original juice to 428.4 g/l in concentrated juice) was enzymatically converted to glucooligosaccharides using 3 U dextransucrase/ml prepared from Leuconostoc mesenteroides at 28 °C. The oligosaccharide synthesis yields were 51 and 47% for the original and the concentrated mandarin juice, respectively. The degree of polymerization of oligosaccharides in the enzyme-modified juice was 2-7. Calories in the original and modified mandarin juice were 433 and 301 kcal/l (30.5% reduction). Compared with the original juice, the enzyme-modified juice showed 82% decrease of insoluble glucan formation by mutansucrase from Streptococcus mutans. A sensory evaluation of the juices revealed that the original and modified mandarin juices had sweetness values of 4.5 and 4.9 and the same values for overall acceptability.

Synthesis and characterization of ampelopsin glucosides using dextransucrase from Leuconostoc mesenteroides B-1299CB4: glucosylation enhancing physicochemical properties.

Novel ampelopsin glucosides (AMPLS-Gs) were enzymatically synthesized and purified using a Sephadex LH-20 column. Each structure of the purified AMPLS-Gs was determined by nuclear magnetic resonance, and the ionic product of AMPLS-G1 was observed at m/z 505 (C21H22O13·Na)⁺ using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. AMPLS-G1 was identified as ampelopsin-4'-O-α-D-glucopyranoside. The optimum condition for AMPLS-G1, determined using response surface methodology, was 70 mM ampelopsin, 150 mM sucrose, and 1 U/mL dextransucrase, which resulted in an AMPLS-G1 yield of 34 g/L. The purified AMPLS-G1 displayed 89-fold increased water solubility and 14.5-fold browning resistance compared to those of AMPLS and competitive inhibition against tyrosinase with a K(i) value of 40.16 µM. This value was smaller than that of AMPLS (K(i)=62.56 µM) and much smaller than that of ß-arbutin (K(i)=514.84 µM), a commercial active ingredient of whitening cosmetics. These results indicate the potential of AMPLS and AMPLS-G1 as superior ingredients for functional cosmetics.

Flavonoid-mediated inhibition of SARS coronavirus 3C-like protease expressed in Pichia pastoris.

The 3C-like protease (3CL(pro)) of severe acute respiratory syndrome associated coronavirus (SARS-CoV) is vital for SARS-CoV replication and is a promising drug target. Recombinant 3CL(pro) was expressed in Pichia pastoris GS115 as a 42 kDa protein that displayed a K ( m ) of 15 ± 2 µM with Dabcyl-KTSAVLQSGFRKME-Edans as substrate. Purified 3CL(pro) was used for inhibition and kinetic assays with seven flavonoid compounds. The IC(50) of six flavonoid compounds were 47-381 µM. Quercetin, epigallocatechin gallate and gallocatechin gallate (GCG) displayed good inhibition toward 3CL(pro) with IC(50) values of 73, 73 and 47 µM, respectively. GCG showed a competitive inhibition pattern with K ( i ) value of 25 ± 1.7 µM. In molecular docking experiments, GCG displayed a binding energy of -14 kcal mol(-1) to the active site of 3CL(pro) and the galloyl moiety at 3-OH position was required for 3CL(pro) inhibition activity.