Enzymatic and Non-Enzymatic Mechanisms Contribute to Lipid Oxidation During Seed Aging.

Storage of seeds is accompanied by loss of germination and oxidation of storage and membrane lipids. A lipidomic analysis revealed that during natural and artificial aging of Arabidopsis seeds, levels of several diacylglycerols and free fatty acids, such as linoleic acid and linolenic acid as well as free oxidized fatty acids and oxygenated triacylglycerols, increased. Lipids can be oxidized by enzymatic or non-enzymatic processes. In the enzymatic pathway, lipoxygenases (LOXs) catalyze the first oxygenation step of polyunsaturated fatty acids. Analysis of lipid levels in mutants with defects in the two 9-LOX genes revealed that the strong increase in free 9-hydroxy- and 9-keto-fatty acids is dependent on LOX1 but not LOX5. Fatty acid oxidation correlated with an aging-induced decrease of germination, raising the question of whether these oxylipins negatively regulate germination. However, seeds of the lox1 mutant were only slightly more tolerant to aging, indicating that 9-LOX products contribute to but are not the major cause of loss of germination during aging. In contrast to free oxidized fatty acids, accumulation of oxygenated triacylglycerols upon accelerated aging was mainly based on non-enzymatic oxidation of seed storage lipids.

Identification and quantitation of the ingredients in a counterfeit Vietnamese herbal medicine against rheumatic diseases.

Counterfeit and/or illegally manufactured drugs and herbal medicines are becoming an increasing problem throughout the world. Internet sales simplify distribution and payment of these falsified drugs. Here we report on a Vietnamese herbal medicine, which was advertised for treatment of rheumatic disease from a religious Vietnamese healer. By means of NMR and LC/MS we found 863mg acetaminophen, 262mg sulfamethoxazole, 42mg indomethacin and less than 1% trimethoprim in a sachet of 2.617g powder content, in addition to some cinnamon bark and phosphate.

Singlet oxygen is the major reactive oxygen species involved in photooxidative damage to plants.

Reactive oxygen species act as signaling molecules but can also directly provoke cellular damage by rapidly oxidizing cellular components, including lipids. We developed a high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry-based quantitative method that allowed us to discriminate between free radical (type I)- and singlet oxygen ((1)O(2); type II)-mediated lipid peroxidation (LPO) signatures by using hydroxy fatty acids as specific reporters. Using this method, we observed that in non-photosynthesizing Arabidopsis (Arabidopsis thaliana) tissues, nonenzymatic LPO was almost exclusively catalyzed by free radicals both under normal and oxidative stress conditions. However, in leaf tissues under optimal growth conditions, (1)O(2) was responsible for more than 80% of the nonenzymatic LPO. In Arabidopsis mutants favoring (1)O(2) production, photooxidative stress led to a dramatic increase of (1)O(2) (type II) LPO that preceded cell death. Furthermore, under all conditions and in mutants that favor the production of superoxide and hydrogen peroxide (two sources for type I LPO reactions), plant cell death was nevertheless always preceded by an increase in (1)O(2)-dependent (type II) LPO. Thus, besides triggering a genetic cell death program, as demonstrated previously with the Arabidopsis fluorescent mutant, (1)O(2) plays a major destructive role during the execution of reactive oxygen species-induced cell death in leaf tissues.