Dabsyl chloride (dimethylaminoazobenzene sulfonyl chloride), a useful chromophoric labeling reagent for amino acids and amines, was developed in this laboratory in 1975. Although several methods have been developed to determine various types of amino acids, a quick and easy method of determining theanine, GABA, and other amino acids has not been developed in one HPLC system. In this paper are analyzed the free amino acid contents of theanine and GABA in different teas (green tea, black tea, oolong tea, Pu-erh tea, and GABA tea) with a dabsylation and reverse phase high-performance liquid chromatography (HPLC) system coupled with a detector at 425 nm absorbance. Two reverse phase columns, Hypersil GOLD and Zorbax ODS, were used and gave different resolutions of dabsyl amino acids in the gradient elution program. The data suggest that the tea source or the steps of tea-making may contribute to the theanine contents variations. High theanine contents of high-mountain tea were observed in both green tea and oolong tea. Furthermore, the raw (natural fermented) Pu-erh tea contained more theanine than ripe (wet fermented) Pu-erh tea, and the GABA contents in normal teas were generally lower than that in GABA tea.

Solanum nigrum Linn (SN) belongs to the Solanaceae family, is a plant growing widely in south Asia, and has been used in traditional folk medicine. It is believed to have antipyretic, diuretic, anticancer, and hepatoprotective effects. During the summertime, this plant has been heavily used to supplement beverages to quench thirst on hot days in Taiwan and several southern Asian countries. In this study, the polyphenols and anthocyanidin in various parts of the SN plant were analyzed by HPLC. The leaves were found to be richer in polyphenols than stem and fruit. SN leaves contained the highest concentration of gentisic acid, luteolin, apigenin, kaempferol, and m-coumaric acid. However, the anthocyanidin existed only in the purple fruits. Additionally, the cytotoxicity of the leaf, stem, or fruit extract was evaluated against cancer cell lines and normal cells. The results showed that AU565 breast cancer cells were more sensitive to the extract. Furthermore, the results demonstrated a significant cytotoxic effect of SN leaf extract on AU565 cells that was mediated via two different mechanisms depending on the exposure concentrations. A low dose of SN leaf extract induced autophagy but not apoptosis. Higher doses (>100 microg/mL) of SN leaf extract could inhibit the level of p-Akt and cause cell death due to the induction of autophagy and apoptosis. However, these findings indicate that SN leaf extract induced cell death in breast cells via two distinct antineoplastic activities, the abilities to induce apoptosis and autophagy, therefore suggesting that it may provide a useful remedy to treat breast cancer.