Although the general mechanisms of lipid oxidation are known, the chemical steps through which photosensitizers and light permeabilize lipid membranes are still poorly understood. Herein we characterized the products of lipid photooxidation and their effects on lipid bilayers, also giving insight into their formation pathways. Our experimental system was designed to allow two phenothiazinium-based photosensitizers (methylene blue, MB, and DO15) to deliver the same amount of singlet oxygen molecules per second to 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine liposome membranes, but with a substantial difference in terms of the extent of direct physical contact with lipid double bonds; that is, DO15 has a 27-times higher colocalization with ω-9 lipid double bonds than MB. Under this condition, DO15 permeabilizes membranes at least 1 order of magnitude more efficiently than MB, a result that was also valid for liposomes made of polyunsaturated lipids. Quantification of reaction products uncovered a mixture of phospholipid hydroperoxides, alcohols, ketones, and aldehydes. Although both photosensitizers allowed the formation of hydroperoxides, the oxidized products that require direct reactions between photosensitizer and lipids were more prevalent in liposomes oxidized by DO15. Membrane permeabilization was always connected with the presence of lipid aldehydes, which cause a substantial decrease in the Gibbs free energy barrier for water permeation. Processes depending on direct contact between photosensitizers and lipids were revealed to be essential for the progress of lipid oxidation and consequently for aldehyde formation, providing a molecular-level explanation of why membrane binding correlates so well with the cell-killing efficiency of photosensitizers.

Amyotrophic lateral sclerosis (ALS) is characterized by progressive loss of upper and lower motor neurons leading to muscle paralysis and death. While a link between dysregulated lipid metabolism and ALS has been proposed, lipidome alterations involved in disease progression are still understudied. Using a rodent model of ALS overexpressing mutant human Cu/Zn-superoxide dismutase gene (SOD1-G93A), we performed a comparative lipidomic analysis in motor cortex and spinal cord tissues of SOD1-G93A and WT rats at asymptomatic (~70 days) and symptomatic stages (~120 days). Interestingly, lipidome alterations in motor cortex were mostly related to age than ALS. In contrast, drastic changes were observed in spinal cord of SOD1-G93A 120d group, including decreased levels of cardiolipin and a 6-fold increase in several cholesteryl esters linked to polyunsaturated fatty acids. Consistent with previous studies, our findings suggest abnormal mitochondria in motor neurons and lipid droplets accumulation in aberrant astrocytes. Although the mechanism leading to cholesteryl esters accumulation remains to be established, we postulate a hypothetical model based on neuroprotection of polyunsaturated fatty acids into lipid droplets in response to increased oxidative stress. Implicated in the pathology of other neurodegenerative diseases, cholesteryl esters appear as attractive targets for further investigations.

Coconut water contains several uncharacterized substances and is widely used in the human consumption. In this paper we detected and quantified ascorbic acid and caffeic acid and total phenolics in several varieties of coconut using HPLS/MS/MS (25.8 ± 0.6 µg/mL and 1.078 ± 0.013 µg/mL and 99.7 µg/mL, respectively, in the green dwarf coconut water, or 10 mg and 539 µg and 39.8 mg for units of coconut consumed, 500 ± 50 mL). The antioxidant potential of four coconut varieties (green dwarf, yellow dwarf, red dwarf and yellow Malaysian) was compared with two industrialized coconut waters and the lyophilized water of the green dwarf variety. All varieties were effective in scavenging the DPPH radical (IC 50 =73 µL) and oxide nitric (0.1 mL with an IP of 29.9%) as well as in inhibiting the in vitro production of thiobarbituric acid reactive substances (1 mL with an IP of 34.4%), highlighting the antioxidant properties of the green dwarf which it is the most common used. In cell culture, the green dwarf water was efficient in protecting against oxidative damages induced by hydrogen peroxide.

Coconut water (CW) is a natural nutritious beverage, which contains several biologically active compounds that are traditionally used in the treatment of diarrhea and rehydration. Several works with CW have been related with antioxidant activity, which is very important in the diabetic state. To evaluate the hypoglycemic and nephroprotective activities of CW, alloxan-induced diabetic rats were pre- and post-treated by gavage with CW (3 mL/kg), caffeic acid (CA) (10 and 15 mg/kg), and acarbose (Acb) (714 μg/kg) during a period of 16 days. Body weight, blood glucose, glycated hemoglobin (HbA1c), and Amadori products in plasma and kidney homogenates were evaluated in all groups and used as parameters for the monitoring of the diabetic state. The results showed that rats of the CW+diabetic group had maintenance in blood glucose compared with the control group (P<.05) in addition to a decrease of HbA1c levels and increase of body weight when compared with the diabetic group rats (P<.05). The animals of the CA and CA+diabetic groups did not have significant variation of body weight (P<.05) during the experiment; however, they showed decrease in their HbA1c and urea levels in plasma as well as Amadori products in kidney homogenates when compared with the diabetic group (P<.05). Our results indicate that CW has multiple beneficial effects in diabetic rats for preventing hyperglycemia and oxidative stress caused by alloxan.

Hepatic disorders such as steatosis and alcoholic steatohepatitis are common diseases that affect thousands of people around the globe. This study aims to identify the main phenol compounds using a new HPLC-ESI + -MS/MS method, to evaluate some oxidative stress parameters and the hepatoprotective action of green dwarf coconut water, caffeic and ascorbic acids on the liver and serum of rats treated with ethanol.The results showed five polyphenols in the lyophilized coconut water spiked with standards: chlorogenic acid (0.18 µM), caffeic acid (1.1 µM), methyl caffeate (0.03 µM), quercetin (0.08 µM) and ferulic acid (0.02 µM) isomers. In the animals, the activity of the serum γ-glutamyltranspeptidase (γ-GT) was reduced to 1.8 I.U/L in the coconut water group, 3.6 I.U/L in the ascorbic acid group and 2.9 I.U/L in the caffeic acid groups, when compared with the ethanol group (5.1 I.U/L, p<0.05). Still in liver, the DNA analysis demonstrated a decrease of oxidized bases compared to ethanol group of 36.2% and 48.0% for pretreated and post treated coconut water group respectively, 42.5% for the caffeic acid group, and 34.5% for the ascorbic acid group. The ascorbic acid was efficient in inhibiting the thiobarbituric acid reactive substances (TBARS) in the liver by 16.5% in comparison with the ethanol group. These data indicate that the green dwarf coconut water, caffeic and ascorbic acids have antioxidant, hepatoprotective and reduced DNA damage properties, thus decreasing the oxidative stress induced by ethanol metabolism.