Phenolic compounds are well-known phytochemicals found in all plants. They consist of simple phenols, benzoic and cinnamic acid, coumarins, tannins, lignins, lignans and flavonoids. Substantial developments in research focused on the extraction, identification and quantification of phenolic compounds as medicinal and/or dietary molecules have occurred over the last 25 years. Organic solvent extraction is the main method used to extract phenolics. Chemical procedures are used to detect the presence of total phenolics, while spectrophotometric and chromatographic techniques are utilized to identify and quantify individual phenolic compounds. This review addresses the application of different methodologies utilized in the analysis of phenolic compounds in plant-based products, including recent technical developments in the quantification of phenolics.

Rice plants exposed to three consecutive days of water stress (−0.5 MPa) show a reduction in male fertility and grain set, which is attributed to increased levels of reactive oxygen species (ROS) and activation of a programmed cell death. This current research was conducted to further investigate the association of sugar metabolism with microspore abortion in rice anthers. Biochemical assays showed that sucrose, glucose and fructose contents were found to be significantly increased in anthers from water stressed plants compared with the control. qRT‐PCR analyses and in situ hybridization of metabolic genes (sugar transporters, invertase and phosphotransferase/kinases) demonstrated that the supply of sugars for developing microspores and the initial steps of sugar utilization e.g. glycolysis, were not repressed. However, it appears that the accumulation of sugars in stressed anthers might involve a reduction of mitochondrial activity during the tricarboxylic acid cycle, which could result in excessive production of ROS and a depletion of the ATP pool. These results also suggest that higher levels of sugars at all stages of anther development seemed to be associated with some measure of protection to the anthers against oxidative stress. Induced expression of sugar transporter genes might have maintained the high levels of sugar in the tapetum and the locules, which alleviated oxidant damage caused by excessive ROS generation. Thus, the increased level of sugars might potentially be a natural response in providing protection against oxidant damage by strengthening the antioxidant system in anthers.

Male gametophyte development of eukaryotic plants in general and rice in particular is especially sensitive to drought. Water deficit during this stage inhibits microspore development resulting in male sterility. To elucidate the molecular mechanism of the phenomenon, a water deficit‐induced experiment was conducted during anther development. Microscopic observations of anther cross‐sections labelled with TdT‐mediated dUTP nick‐end labelling (TUNEL) indicated programmed cell death (PCD) signals after three consecutive days of water deficit. PCD is a biological process featured by the fragmentation of genomic DNA and plays an important role in plant reproduction. PCD is often concurrent with biochemical and physical changes in the cytoplasm, nucleus and plasma membrane of the cells. In this study, biochemical assays showed depletion of the adenosine triphosphate pool, increased concentration of hydrogen peroxide (ROS) and down‐regulation of antioxidant transcripts in anthers. We argue that the interplay between PCD and oxidative stress in anthers might be a cause of pollen sterility in drought‐stressed rice.

The N-terminal SH4 domain of Src family kinases is responsible for promoting membrane binding and plasma membrane targeting. Most Src family kinases contain an N-terminal Met-Gly-Cys consensus sequence that undergoes dual acylation with myristate and palmitate after removal of methionine. Previous studies of Src family kinase fatty acylation have relied on radiolabeling of cells with radioactive fatty acids. Although this method is useful for verifying that a given fatty acid is attached to a protein, it does not reveal whether other fatty acids or other modifying groups are attached to the protein. Here we use matrix-assisted laser desorption/ ionization-time of flight (MALDI-TOF) mass spectrometry to identify fatty acylated species of the Src family kinase Fyn. Our results reveal that Fyn is efficiently myristoylated and that some of the myristoylated proteins are also heterogeneously S-acylated with palmitate, palmitoleate, stearate, or oleate. Furthermore, we show for the first time that Fyn is trimethylated at lysine residues 7 and/or 9 within its N-terminal region. Both myristoylation and palmitoylation were required for methylation of Fyn. However, a general methylation inhibitor had no inhibitory effect on myristoylation and palmitoylation of Fyn, suggesting that methylation occurs after myristoylation and palmitoylation. Lysine mutants of Fyn that could not be methylated failed to promote cell adhesion and spreading, suggesting that methylation is important for Fyn function.Nearly all Src family kinases (SFKs) 1 contain an N-terminal Met-Gly-Cys consensus sequence that promotes dual fatty acylation with myristate and palmitate. After removal of Met, myristate is co-translationally attached to the N-terminal Gly-2 via amide linkage, whereas palmitoylation of Cys-3 occurs post-translationally via a thioester linkage (1, 2). To date, studies of acylation of SFKs have been based solely on incorporation of radioactive myristate or palmitate. No study has directly examined the nature of the attached fatty acids in vivo. We recently exploited mass spectrometry to identify S-acylated species of the palmitoylated protein neuromodulin (GAP43) (3). Here we extend this approach to study the modifications on dually myristoylated and palmitoylated proteins, such as SFKs. Our results indicate that the SFK Fyn is efficiently myristoylated and that some of the myristoylated Fyn is also heterogeneously S-acylated with different dietary fatty acids.During the course of this study, we identified an additional modification on Fyn: trimethylation of a lysine residue(s). Protein methylation involves transfer of a methyl group from Sadenosylmethionine to arginine, lysine, histidine, or carboxyl groups on proteins. Recently, protein methylation has emerged as an intensively studied regulatory modification of proteins. For example, carboxyl methylation of Ras is important for plasma membrane localization of Ras proteins (4). Most heterogeneous nuclear ribonucleoproteins contain multiple arginineglycine repeats and are methylated...

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