Molecular and Metabolic Changes under Environmental Stresses: The Biosynthesis of Quality Components in Preharvest Tea Shoots

A semi-quantitative histochemical method for assessment of biochemical responses to osmotic stress in Coffea arabica leaf disks

A simple method set for assessing biochemical changes associated with osmotic stress responses was developed using coffee (Coffea arabica L.) leaf disks. Stress was induced by polyethylene glycol (PEG) exposure. Quantitative evaluation of tissue physiological stress parameters was carried out using analytical methods to validate the conversion of classic qualitative histochemical tests for localizing lipid peroxidation, hydrogen peroxide, and total xanthine alkaloids into semi-quantitative assays. Relative electrolyte leakage (EL%) and chlorophyll content (SPAD index) were also recorded. EL% levels of treated disks were higher than those of control ones, whereas SPAD indexes were comparable. Histochemical localization indicated that levels of lipid peroxidation, H2O2, and total xanthines were also higher under osmotic stress than in control conditions. Semi-quantitative data obtained by image processing of histochemical staining consistently matched quantitative evaluations. Chromatographic analyses revealed that theophylline and caffeine concentrations increased in the presence of PEG, whereas theobromine remained constant in relation to the control. The methods herein described can be useful to rapidly acquire initial data regarding biochemical osmotic stress responses in coffee tissues based on simple staining and imaging steps. Moreover, it is likely that the same method may be applicable to other types of stresses and plant species upon minor adjustments.

Discriminative Chemical Profiles of Shan Tuyet Tea (Camellia sinensis var. Shan) and Sinensis Tea (Camellia sinensis var. sinensis) Collected in Ta Xua, Son La, Vietnam and Their Correlation With Antioxidant Activity

Chè Shan Tuyet ( Camellia sinensis var. Shan) is one of the precious tea resources of Vietnam; however, there is little research on its chemical composition. The purpose of this study was to characterize the main quality components, such as free amino acids and catechins, in Camellia sinensis var. Shan and Camellia sinensis var. sinensis collected in the high mountain of Ta Xua, Son La, Vietnam by using an amino acid analyzer and liquid chromatography coupled with tandem mass spectrometry, respectively. Principal component analysis (PCA) discrimination analysis of chemical profiles revealed a clear metabolic difference between the young leaves of Shan Tuyet tea and mature leaves of the same variety and of sinensis tea. The amino acids serine, glutamic acid, arginine, ornithine, and aspartic acid contributed mainly to the discrimination and could be considered biomarkers for Shan Tuyet tea. The levels of caffeine and 7 catechins, catechin, catechin 3-gallate, epicatechin, epicatechin-3-gallate, epigallocatechin 3-gallate, gallocatechin, and gallocatechin 3-gallate, in young leaves of Shan Tuyet tea were significantly higher than in the other types. Notably, the pair correlation among catechins revealed strong coefficients of the epistructures and non-epistructures, which suggested that these compounds can be converted naturally to each other. The strong correlation between epicatechin-3-gallate and catechin 3-gallate with antiradical ABTS activity of Shan Tuyet tea leaves indicates that these 2 catechins are mainly responsible for the antioxidant activity. This is the first report on the bioactive compounds of Shan Tuyet tea, as well as its potential for the production of health supplements.