Aldoses are one of the most important structural components of biomolecules, such as polysaccharides, nucleic acids, glycolipids and glycoproteins. In addition, numerous secondary metabolites in plants, such as terpenoids, steroids, and flavonoids, exist as glycosides, which conjugate with aldoses. Aldoses are optically active compounds, and confirmation of absolute configuration is required in natural product chemistry. Measurement of specific rotations of pure samples is the most reliable method, although this is impractical in many cases because only limited amounts of samples are available. Analysis using a column with a chiral stationary phase developed for the separation of enantiomers, or an HPLC system equipped with an optical rotation detector and a column specified for sugar analysis, can be applied 1,2) ; however, the latter method is not applicable to mixtures of Dand L-enantiomers. Identification of sugars with small optical rotation may be also difficult. Methods using capillary electrophoresis have also been developed, 3,4) but these methods require specialized equipment or columns that are unfamiliar to most organic chemistry laboratories. Some methods based on conversion of aldose enantiomers to diastereomeric derivatives through coupling to an optically active reagent have been developed 5,6) ; however, there are not many methods applicable to the widely used HPLC systems equipped with a UV detector and C 18 reversed-phase column. This paper describes a new method to discriminate between aldose enantiomers using a usual HPLC system. Results and DiscussionHara et al. developed an excellent method using gas chromatography, in which enantiomeric aldoses were converted to trimethylsilyl ethers of methyl 2-(polyhydroxyalkyl)-thiazolidine-4(R)-carboxylates. 7) In order to apply this method to HPLC analysis, we converted the thiazolizine derivatives to arylthiocarbamate (3, 4) by reaction with arylisothiocyanates.The reaction procedure is very simple: sugar samples, such as D-and L-glucoses (1, 2, respectively), are heated with L-cycteine methyl ester in pyridine at 60°C for 60 min, then arylisothiocyanate was added to the reaction mixture and further reacted at 60°C for 60 min. Then, the reaction mixture was directly analyzed by standard C 18 HPLC and detected by a UV detector (at 250 nm). When phenylisothiocyanate was used, the retention time (t R ) of the derivatives of D-and L-glucoses were 16.35 and 15.37 min, respectively. The derivatives of D-and L-glucoses (3, 4, respectively) were isolated and their structures were determined by 1 H-and 13 C-NMR spectra and FAB-MS analyses. Although the production of two diastereomers, which have an opposite configuration at the sugar C-1 position, was expected from each enantiomer, the 1 H-and 13 C-NMR spectra showed that one of the two possible diastereomers was produced preferably in the case of glucose.When the reaction mixture was stored at room temperature for a few days, the derivatives decomposed to give thiohydantoin compounds by elimination of metha...

Recently, many biochemical and epidemiologic studies have revealed that polyphenols of various foods and herbs are beneficial to human health, and some extracts of polyphenolrich plants, such as green tea and grape seed, have been applied to functional foods or supplements. The potent biological activities of green tea polyphenols in, for example, cancer and cardiovascular disease prevention, 1) have in particular been attracting scientists in medicinal and pharmaceutical fields. Tea polyphenols were also shown to have antibacterial, 2-5) antiviral, 6) and antifungal activities 7) in addition to their inhibitory effects on exotoxins. 4,8) In these studies, only a few types of cultures such as from the American Type Culture Collection (ATCC) were examined according to different protocols.2,5,9,10) And therefore differences in susceptibility against the same species were indicated. 11)These differences were partly ascribable to the limited number of trial strains used in previous studies. Furthermore, in addition to tea polyphenols, other types of polyphenols, such as hydrolyzable and condensed tannins, are widely distributed in the plant kingdom and have the potential to be functional material. In the present study, we examined the antibacterial activities of 10 different plant polyphenols by comparing their minimum inhibitory concentrations (MICs) against a total of 96 strains of four groups of food-borne pathogenic bacteria including gram-positive and gram-negative species. Taking into consideration the future application of the results in the environmental and sanitation fields, we selected polyphenols that can be obtained in large amounts from plant material. MATERIALS AND METHODSChemicals Epigallocatechin (EGC, 1) and epigallocatechin-3-O-gallate (EGCg, 2) were isolated from commercial green tea, 12) punicalagin (3) was isolated from the peel of Punica granatum, 13) tannic acid (4) was purchased from Kanto Chemical Co. (Tokyo, Japan), castalagin (5) was isolated from wood of Castanea crenata, 14) and prodelphinidin oligomers (6) were isolated from the bark of Elaeocarpus sylvestris var. ellipticus; an aqueous acetone extract of the dried bark was separated by Sephadex LH-20 column chromatography with H 2 O containing increasing proportions of MeOH and finally with H 2 O-acetone (1 : 1, v/v). Prodelphinidin oligomers were then eluted out with 80-100% MeOH and aqueous acetone. Thiol degradation of 6 with mercaptoethanol-HCl 15) showed that this prodelphinidin is composed of EGC and EGCg, and the molecular weight of the peracetate was estimated to be 2000 daltons (peak top molecular weight) by gel permeation chromatography with a TSK-gel G4000H6 column (TOSOH) using polystylene as a standard. Geraniin (7) was isolated from the leaves of E. sylvestris var. ellipticus, 16) and loquat procyanidins (8) were isolated from the seeds of Eriobotrya japonica; fresh seeds were extracted with 80% acetone-H 2 O, and the extract was separated on a Diaion HP-20 column using H 2 O containing increasing amounts of MeOH, which ...

Recently, many biochemical and epidemiological studies have revealed that polyphenols of various foods and herbs have benefits to human health, and some extracts of polyphenol-rich plants, such as green tea and grape seed, have been added to foods or supplements. The antibacterial activity of various plant polyphenols and plant extracts have also been evaluated in several pharmaceutical studies. 1,2) Although tea polyphenols and their extracts have been examined in detail, [3][4][5][6] other extracts of polyphenol-rich plants have not been properly evaluated, because the activity of their chemical constituents has not been clearly demonstrated. 7,8) Many reports on the antibacterial activity of pure polyphenols have been published, 4,[9][10][11][12] however, each result was not able to be compared directly because different methods of evaluation were applied and various bacterial species were used. In order to overcome this problem, we compared the activity of a wide variety of polyphenols against many bacterial species to clarify their antibacterial spectrum, using the same standard method of the minimum inhibitory concentration (MIC). As a result, we found a relatively simple structure-activity relationship, and it was applied to the plant extracts containing various types of polyphenols. MATERIALS AND METHODSChemicals Twenty-two pure or partially pure polyphenols and 26 plant extracts were used in this study (Fig. 1). Polyphenols 1-10 were the same as in our previous study. 12)Epigallocatechin (EGC, 1) and epigallocatechin-3-O-gallate (EGCg, 2) were isolated from commercial green tea; punicalagin (3) was isolated from the peel of Punica granatum; tannic acid (4) was purchased from Kanto Chemical Co., Japan; castalagin (5) was isolated from the wood of Castanea crenata; and prodelphinidins (6) were isolated from the bark of Elaeocarpus sylvestris var. ellipticus; geraniin (7) was isolated from the leaves of E. sylvestris var. ellipticus; loquat procyanidins (8) were isolated from the seeds of Eriobotrya japonica; theaflavins (9) was obtained from black tea; and loquat-treated green tea polyphenols (10) were prepared by treatment of commercial green tea with unripe loquat fruit. Gallic acid monohydrate (11) was purchased from Wako Pure Chemical Industries, Japan. Thearubigin (12) was prepared from black tea as follows: aqueous acetone extract was successively partitioned with AcOEt and n-BuOH. The nBuOH layer was concentrated and subjected to Sephadex LH-20 column chromatography. Elution of 50% acetone yielded 12. (ϩ)-Catechin (13) and (Ϫ)-epicatechin gallate (ECg, 14) were isolated from gambir and green tea, respectively. Myricitrin (15) and rutin (16) were obtained from bark of Myrica rubra and flower bud of Sophora japonica, respectively. Theaflavin mixture (17) was separated from AcOEt soluble fractions of aqueous acetone extracts of black tea. Pyrocatechol (18), pyrogallol (19), protocatechuic acid (20), and caffeic acid (21) were purchased from Sigma Aldrich Japan. Resveratrol (22) was isolated from dried...

Oxidation products of (-)-epicatechin and (-)-epigallocatechin by treatment with homogenates of 62 plants belonging to 49 families were compared. Forty-six plants were capable of synthesizing theaflavin, a black tea pigment, regardless of whether they contained catechins. Loquat, Japanese pear, and blueberry had activities higher than that of fresh tea leaves after 5 h of treatment; furthermore, these plants oxidized theaflavin to theanaphthoquinone. An additional new metabolite, dehydrotheasinensin, was generated on treatment with fresh tea leaves, eggplant, and unripened Japanese orange. Evidence for the oxidation of epigallocatechin and theaflavin by electron transfer to epicatechin quinone was demonstrated in a time course study using bananas and trapping the quinone intermediates as glutathione conjugates.

After artificial removal of the astringency from persimmon fruit by treatment with ethanol, thiol-promoted degradation of the insolubilized proanthocyanidin polymers with 2-sulfanylethanol yielded 4p-(2hydroxyethylsulfanyl) -6-and -8-[ 1 -(2-hydroxyethylsulfanyl)ethyl] -flavan-3-ols 9-1 4. Furthermore, when deuteriated ethanol was used for de-astringency, the deuterium atoms were incorporated into the C, unit attached to the A-ring of these compounds. These findings evidently show that acetaldehyde formed in situ from ethanol plays an important role in polymerization (insolubilization) of water-soluble proanthocyanidins, causing the loss of astringency. OH HO 1 R = H 2 R=galloyl OH 3 R = H 4 R=galloyl OH SCH,CH20H 5 R ' = R 2 = H 6 R' = galloyl, I# = H 7 R' = H, R2 = galloyl 8 R' = R2 = galloyl compounds 9a, b; 10a, b; lla, b; 12a, b; 13a, b; and 14a, b, which