In this study, three epigallocatechin gallate glycosides were synthesized by the acceptor reaction of a glucansucrase produced by Leuconostoc mesenteroides B-1299CB with epigallocatechin gallate (EGCG) and sucrose. Each of these glycosides was then purified, and the structures were assigned as follows: epigallocatechin gallate 7-O-alpha-D-glucopyranoside (EGCG-G1); epigallocatechin gallate 4'-O-alpha-D-glucopyranoside (EGCG-G1'); and epigallocatechin gallate 7,4'-O-alpha-D-glucopyranoside (EGCG-G2). One of these compounds (EGCG-G1) was a novel compound. The EGCG glycosides exhibited similar or slower antioxidant effects, depending on their structures (EGCG > or = EGCG-G1 > EGCG-G1' > EGCG-G2), and also manifested a higher degree of browning resistance than was previously noted in EGCG. Also, EGCG-G1, EGCG-G1', and EGCG-G2 were 49, 55, and 114 times as water soluble, respectively, as EGCG.

Diabetes is an emerging health problem worldwide. The incidence of type 2 diabetes has dramatically increased and is expected to increase more rapidly in the future. Most patients with type 2 diabetes suffer from obesity and diabetes-related complications, including cardiovascular disease and hepatic steatosis. It has been proposed that simple sugar consumption is one of the major risk factors in the development of diabetes. Hence, the replacement of sugars with a low glycemic response would be an effective strategy to prevent type 2 diabetes. Accumulating evidence demonstrates that D-psicose, which has 70% the sweetness of sucrose and no calories, is a functional sugar exerting several health benefits preventing the development of diabetes. Although D-psicose presents in small amounts in natural products, a recent new technique using biocatalyst sources enables large-scale D-psicose production. More importantly, several clinical and animal studies demonstrated that D-psicose has hypoglycemic, hypolipidemic, and antioxidant activities, which make it an ideal candidate for preventing diabetes and related health concerns. This review will summarize the protective effects of D-psicose against type 2 diabetes and its complications, suggesting its potential benefits as a sucrose substitute.

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The conversion yield of D-psicose from D-fructose by a D-psicose 3-epimerase from Agrobacterium tumefaciens increased with increasing molar ratios of borate to fructose, up to a ratio of 0.6. The formation of the psicose-borate complex was the result of the higher binding affinity of borate for psicose than for fructose. The formed psicose-borate complex did not participate in the conversion reaction, acting instead as if the product had been removed. Thus, more fructose was converted to psicose in order to restore the equilibrium. The maximum conversion yield of psicose with borate was about twofold that obtained without borate and occurred at a 0.6 molar ratio of borate to fructose. Above this ratio, the conversion yield decreased with increasing ratios, because the amount of fructose available decreased through the formation of the initial fructose-borate complex. The structures of the two sugar-borate complexes, determined by nuclear magnetic resonance spectroscopy, were ␣-D-psicofuranose cis-C-3,4 diol borate and ␤-D-fructopyranose cis-C-4,5 diol borate.D-Psicose (D-ribo-2-hexulose, or D-allulose), a carbon-3 epimer of D-fructose, is present as a nonfermentable constituent of cane molasses (2), a sugar moiety of the nucleoside antibiotic psicofuranine (9), and a free sugar in wheat (33) and Itea plants (15). The sugar is a noncaloric sweetener for weight reduction (31) based on its suppression of hepatic lipogenous enzyme activity (30). Psicose can be chemically synthesized from fructose by using a molybdate ion catalyst (1), by producing it from 1,2:4,5-di-o-isopropylidene-␤-D-fructopyranose (32), or by boiling fructose in ethanol and triethylamine (8). The biological conversion of fructose to psicose has been studied in recent years using only two enzymes, Agrobacterium tumefaciens D-psicose 3-epimerase (23-25) and Pseudomonas cichorii D-tagatose 3-epimerase (16-18, 37).In aqueous solution, boron exists as either boric acid [B(OH) 3 ] or borate [B(OH) 4 Ϫ ] with a pK a of 9.2 (22), although more borate than boric acid is formed (20). The formation of borate complexes with diol-containing compounds such as carbohydrates has been studied previously for its potential applications in various fields of science and technology (7, 41). The ketoses lactulose, maltulose, and cellobiulose are chemically synthesized from the aldoses lactose, maltose, and cellobiose, respectively, in high-yield isomerization reactions carried out in alkaline solutions containing borate (12, 13).Borate can be used to analyze mixtures of ribose, arabinose, and ribulose by high-performance liquid chromatography (HPLC) using an ion exclusion chromatography column (7). Initially, the sugar retention times are very close to one another, but ribose, arabinose, and ribulose are better separated by increasing the borate concentration in the eluent, owing to the different degrees with which borate forms complexes with the different carbohydrates. The migration of some carbohydrates during thin-layer chromatography (TLC) is decreased by solven...

The amplification of gltA gene encoding citrate synthase of TCA cycle was required for the efficient conversion of acetyl-CoA, generated during vanillin production from ferulic acid, to CoA, which is essential for vanillin production. Vanillin of 1.98 g/L was produced from the E. coli DH5alpha (pTAHEF-gltA) with gltA amplification in 48 h of culture at 3.0 g/L of ferulic acid, which was about twofold higher than the vanillin production of 0.91 g/L obtained by the E. coli DH5alpha (pTAHEF) without gltA amplification. The icdA gene encoding isocitrate dehydrogenase of TCA cycle was deleted to make the vanillin producing E. coli utilize glyoxylate bypass which enables more efficient conversion of acetyl-CoA to CoA in comparison with TCA cycle. The production of vanillin by the icdA null mutant of E. coli BW25113 harboring pTAHEF was enhanced by 2.6 times. The gltA amplification of the glyoxylate bypass in the icdA null mutant remarkably increased the production rate of vanillin with a little increase in the amount of vanillin production. The real synergistic effect of gltA amplification and icdA deletion was observed with use of XAD-2 resin reducing the toxicity of vanillin produced during culture. Vanillin of 5.14 g/L was produced in 24 h of the culture with molar conversion yield of 86.6%, which is the highest so far in vanillin production from ferulic acid using recombinant E. coli.