Effect of dihydrokainate on the antitumor activity of doxorubicin

Photo-induced synthesis of Axinastatin 3 analogs, the secondary structures and their in vitro antitumor activities

Cyclic peptides combine several favorable properties such as good binding affinity, target selectivity and low toxicity that make them an attractive modality for drug development. In an effort to identify what conformation could be accounting for the bioactive disparity of natural and synthetic cyclic peptides, some structurally-constrained analogs of cyclopeptide Axinastatin 3 were prepared by photo-induced single electron transfer (SET) reaction. Detailed stereochemistry study was performed by experimental electronic circular dichroism combined with theoretical calculations. Our study suggested that the cyclopeptide 1 with βI-turn presented stronger antitumor activity comparing with those without such secondary structures. Moreover, a rare 'π helix unit' (compound 3) was realized because of the constrained cyclic structure, which could be considered an important research object for future study of unique helix secondary structures.

Effects of theanine on growth of human lung cancer and leukemia cells as well as migration and invasion of human lung cancer cells

The aim of this study is to investigate the effects of theanine, a tea characteristic amino acid, on human lung cancer and leukemia cells. In the present study, we have demonstrated that theanine suppressed the in vitro and ex vivo growth of human non-small cell lung cancer A549 and leukemia K562 cell lines in dose- and time-dependant manners. In addition, theanine displayed the inhibitory effect on the migration of A549 cells. More importantly, theanine enhanced the anticancer activity of anticancer agents such as trichostatin A (the histone deacetylase inhibitor), berbamine and norcantharidin (the anticancer drugs in China) by strongly reducing the viability and/or migration rate in A549 cells. In addition, theanine significantly suppressed A549 cell invasion. Suppression of A549 cell migration may be one of the important mechanisms of action of theanine against the A549 cell invasion. Our present results suggest that theanine may have the wide therapeutic and/or adjuvant therapeutic application in the treatment of human lung cancer and leukemia.

Application of CE in hydrodynamically closed systems for analysis of bioactive compounds in food

CE is a family of electrokinetic separation techniques that separate compounds based upon differences in electrophoretic mobilities, phase partitioning, pI, molecular size, or a combination of one or several of these properties. CE has been used in several modes to analyze and characterize a wide variety of analytes from simple inorganic ions, small organic molecules, peptides, proteins, nucleic acids to virus, microbes and particles. Food consists of a complex mixture of a variety of components, many of which are biologically active. Components classified as "nutrients" are essential for growth, maintenance, and repair of the body. Other food constituents, typically occurring in small quantities, are classified as "biologically active substances" and they have beneficial or harmful effects on human health. There are two types of biologically active substances in food - naturally occurring and food additives. The bioactive compounds of food that will be mentioned in this review are inorganic and organic acids, amino acids, vitamins, phenolic compounds, biogenic amines, antinutrients, toxins, etc. This review is focused on the application of CE with hydrodynamically closed system (suppression of EOF) for the analysis of the above-mentioned compounds. CE can be an alternative method to HPLC or other methods for analysis of bioactive compounds in food. The main advantages of CE are low running cost (at least ten times than HPLC) and consideration to environment (hundreds of microliters of diluted water based electrolyte per analysis).

Isotachophoretic determination of theanine

Free amino acids, the key quality components of tea, are contained in higher amounts in higher grade teas. Among free amino acids in tea, the content of theanine, which is the amino acid of the highest amount, shows high correlation to the price of green tea. A capillary isotachophoresis (CITP) method was developed for the analysis of L-theanine in tea and food supplements. The optimized electrolyte system was following: 0.01 mol/l HCl + 0.02 mol/l TRIS + 0.05% HEC (leading electrolyte), 0.01 mol/L-valine + barium hydroxide to pH 10 (terminating electrolyte). Good separation of L-theanine from other components of sample was achieved within 20 min. Method characteristics, i.e., linearity (0–200 mg/l), accuracy (99 ± 2 %), intra-assay (1.5 %), quantification limit (2 mg/l), and detection limit (0.7 mg/l) were determined. Sufficient sensitivity, low labouriousness (extraction only) and low running cost are important attributes of this method. It was proved that the developed method is suitable for the routine analysis of L-theanine in green tea and food supplements containing green tea extract.

Medicinal Benefits of Green Tea: Part II. Review of Anticancer Properties

Currently there is wide interest in the medicinal benefits of green tea (Camellia sinensis). Tea is one of the most widely consumed beverages in the world, and extracts of tea leaves are also sold as dietary supplements. Green tea extracts contain a unique set of catechins that possess biologic activity in antioxidant, antiangiogenesis, and antiproliferative assays that are potentially relevant to the prevention and treatment of various forms of cancer. With the increasing interest in the health properties of tea and a significant rise in their scientific investigation, it is the aim of this review to summarize recent findings on the anticancer and medicinal properties of green tea, focusing on the biologic properties of the major tea catechin, (-)-epigallocatechin and its antitumor properties.

A novel assay method for theanine synthetase activity by capillary electrophoresis

The determination of theanine has been performed by micellar electrokinetic capillary chromatography (MECC) using 2,4-dinitrofluorobenzene (DNFB) as a derivative reagent. To achieve the separation, a fused-silica capillary column was used with a borax buffer at 0.03 mol/L pH 9.8 (containing Brij35 and isopropanol) at 17 degrees C with detection wave length at 360 nm. The factors affecting the efficiency of the sample separation were examined simultaneously. A 40-min reaction at 35 degrees C between l-glutamate and ethylamine (with Tris-HCl buffer, pH 7.5) was investigated using the theanine synthetase from budding tea seeds. A novel method for the analysis of theanine synthetase activity based on MECC was established. The method shows mean recovery ranged from 87.1 to 105.3% and linearity ranged from 0.2 to 5.0 mmol/L.

Theanine and glutamate transporter inhibitors enhance the antitumor efficacy of chemotherapeutic agents

Biochemical modulation has played an important role in the development of cancer chemotherapy. The combined effects of theanine, a specific amino acid in green tea, and glutamate transporter inhibitors on the antitumor activity of doxorubicin (DOX), were investigated and we clarified the biochemical mechanisms of action of these modulators. In M5076 ovarian sarcoma-bearing mice, theanine significantly enhanced the inhibitory effect of DOX on tumor growth and increased the DOX concentration in the tumor, compared to DOX-alone group. Furthermore, the oral administration of theanine or green tea similarly enhanced the antitumor activity of DOX. Moreover, the combination of theanine with DOX suppressed the hepatic metastasis of ovarian sarcoma. In contrast, an increase in DOX concentration was not observed in normal tissues, such as liver and heart. Namely, theanine did not enhance, rather it tended to normalize the increase of lipid peroxide (LPO) levels and reduction of glutathione peroxidase activity as indicators of the DOX-induced side toxicity. On the other hand, in vitro experiments proved that theanine inhibited the efflux of DOX from tumor cells, supporting a theanine-induced increase in the DOX concentration in tumors in vivo. Moreover, theanine significantly inhibited the glutamate uptake by M5076 cells similar to specific inhibitors. Two astrocytic high-affinity glutamate transporters, GLAST and GLT-1, were expressed in M5076 cells. These results suggested that the inhibition of DOX efflux was induced by theanine-mediated inhibition of glutamate transporters. The reduction in the concentration of glutamate in tumor cells caused by theanine induced decreases in the intracellular glutathione (GSH) and GS-DOX conjugate levels. As the expression of MRP5 in M5076 cells was confirmed, it is suggested that the GS-DOX conjugate was transported extracellularly via the MRP5/GS-X pump in M5076 cells and that theanine affected this route. Namely, theanine increases the concentration of DOX in a tumor in vivo through inhibition of the glutamate transporter via the GS-X pump. Similarly, dihydrokainate (DHK) and L-serine-O-sulfate (SOS), specific glutamate transporter inhibitors, indicated the enhancement of the DOX antitumor activity via inhibition of glutamate uptake. Therefore, we revealed the novel mechanism of enhancement of antitumor efficacy of DOX via the inhibition of glutamate transporters. Similarly, theanine enhanced the antitumor activities of other anthracyclines, cisplatin and irinotecan. Consequently, the modulating effect of theanine on the efficacy of antitumor agents is expected to be applicable in clinical cancer chemotherapy.