Analysis and functionality of major polyphenolic components of Polygonum cuspidatum (itadori).

Polygonum cuspidatum has been broadly utilized as a herbal medicine in Asia, but the outline of the polyphenol compounds in the plant has not been characterized well. In the present study, the major polyphenolic components were isolated from the roots of P. cuspidatum, and identified as resveratrol and its glucosides, resveratroloside and polydatin. On the other hand, chlorogenic acid was found to be one of the polyphenolic components in the leaves and stems of the plant. Next, we elucidated that resveratrol derivatives and chlorogenic acid exhibit α-glucosidase inhibitory activities, and resveratroloside exhibits the same inhibitory activity as quercetin does. Furthermore, DPPH radical scavenging activities of antioxidants including resveratrol derivatives and chlorogenic acid derivatives were examined by initial rate analyses of their reactions. Subsequently, it was revealed that resveratrol derivatives have slow-acting effects on the radical scavenging activity and that chlorogenic acid derivatives exhibit very fast-acting effects.

Functional expression of single-chain antibody to leukotriene C(4).

Leukotriene C(4) (LTC(4)) is synthesized by binding of glutathione to LTA(4), an epoxide derived from arachidonic acid, and further metabolized to LTD(4) and LTE(4). We previously prepared a monoclonal antibody with a high affinity and specificity to LTC(4). To explore the structure of the antigen-binding site of a monoclonal antibody against LTC(4) (mAbLTC), we isolated full-length cDNAs for heavy and light chains of mAbLTC. The heavy and light chains consisted of 461 and 238 amino acids including a signal peptide with molecular weights of 51,089 and 26,340, respectively. An expression plasmid encoding a single-chain antibody comprising variable regions of mAbLTC heavy and light chains (scFvLTC) was constructed and expressed in COS-7 cells. The recombinant scFvLTC showed a high affinity with LTC(4) comparable to mAbLTC. The scFvLTC also bound to LTD(4) and LTE(4) with 48% and 17% reactivities, respectively, as compared with LTC(4) binding, whereas the antibody showed almost no affinity for LTB(4).

Antiproliferative activity of guava leaf extract via inhibition of prostaglandin endoperoxide H synthase isoforms.

Prostaglandin endoperoxide H synthase (PGHS) is a key enzyme for the synthesis of prostaglandins (PGs) which play important roles in inflammation and carcinogenesis. Because the extract from Psidium guajava is known to have a variety of beneficial effects on our body including the anti-inflammatory, antioxidative and antiproliferative activities, we investigated whether the extract inhibited the catalytic activity of the two PGHS isoforms using linoleic acid as an alternative substrate. The guava leaf extract inhibited the cyclooxygenase reaction of recombinant human PGHS-1 and PGHS-2 as assessed by conversion of linoleic acid to 9- and 13-hydroxyoctadecadienoic acids (HODEs). The guava leaf extract also inhibited the PG hydroperoxidase activity of PGHS-1, which was not affected by nonsteroidal anti-inflammatory drugs (NSAIDs). Quercetin which was one of the major components not only inhibited the cyclooxygenase activity of both isoforms but also partially inhibited the PG hydroperoxidase activity. Overexpression of human PGHS-1 and PGHS-2 in the human colon carcinoma cells increased the DNA synthesis rate as compared with mock-transfected cells which did not express any isoforms. The guava leaf extract not only inhibited the PGE(2) synthesis but also suppressed the DNA synthesis rate in the PGHS-1- and PGHS-2-expressing cells to the same level as mock-transfected cells. These results demonstrate the antiproliferative activity of the guava leaf extract which is at least in part caused by inhibition of the catalytic activity of PGHS isoforms.

Characterization of inhibitors of postprandial hyperglycemia from the leaves of Nerium indicum.

Nerium indicum is an India-Pakistan-originated shrub belonging to the oleander family. The ingestion of leaves of N. indicum before a meal is known to effect the lowering of postprandial glucose levels in Type II diabetic patients and this plant is now used as a folk remedy for Type II diabetes in some regions of Pakistan. In the present study, the hot-water extract of N. indicum leaves was found to reduce the postprandial rise in the blood glucose when maltose or sucrose was loaded in rats. It was also found that the extract strongly inhibited alpha-glucosidase, suggesting that the suppression of the postprandial rise in the blood glucose is due to the occurrence of some inhibitors of alpha-glucosidase in the leaves. We, therefore, tried to isolate the active principles from the leaf extract, using alpha-glucosidase-inhibitory activity as the index. Employing Sephadex G-15, silica gel and reversed-phase HPLC, we isolated two active compounds. The UV, mass and NMR spectrometric analyses established that the chemical structures of these compounds are 3-O-caffeoylquinic acid (chlorogenic acid) and its structural isomer, 5-O-caffeoylquinic acid. Both compounds were shown to inhibit alpha-glucosidases in a non-competitive manner. The authentic chlorogenic acid was found to suppress the postprandial rise in the blood glucose in rats and also inhibited the absorption of the glucose moiety from maltose and glucose in the everted gut sac system prepared from rat intestine. These results demonstrate that chlorogenic acid is one of the major anti-hyperglycemic principles present in the leaves of N. indicum. Furthermore, among polyphenol compounds tested, quercetin and catechins were shown to have strong inhibitory activity against alpha-glucosidase.

Effect of a hypolipidemic drug, Di (2-ethylhexyl) phthalate, on mRNA-expression associated fatty acid and acetate metabolism in rat tissues.

Di (2-ehtylhexyl) phthalate (DEHP) is a peroxisome proliferator and a drug having a hypolipidemic effect. The body-weight change of rats treated with DEHP was lower than that of rats in an untreated control group. Expressions of long-chain acyl-CoA dehydrogenase and 3-ketoacyl-CoA thiolase, which are involved in fatty acid oxidation and acetate formation in mitochondria, showed an increase in the liver and testes of rats treated with DEHP. The expression of acetyl-CoA synthetase 1 was significantly decreased in the testes and relatively decreased in the liver, while the expression of acetyl-CoA synthetase 2 was significantly increased in the heart. Furthermore, the expressions of acetyl-CoA carboxylase in heart and testes showed a tendency to decrease. From these results, it is suggested that DEHP-treatment increased fatty acid oxidation and acetate formation in liver and testes, and that acetate utilization was increased in peripheral tissues such as the heart.