Main Colonic Metabolites from Coffee Chlorogenic Acid May Counteract Tumor Necrosis Factor-α-Induced Inflammation and Oxidative Stress in 3T3-L1 Cells

Obesity is coupled with an altered redox state and low-level inflammation. Oxidative stress may increase pre-adipocyte proliferation, adipocyte differentiation and mature adipocyte size. Regarding inflammation, the dysregulation of cytokine production by adipose tissue takes place in obesity, which is promoted by oxidative stress. Polyphenols may exert a positive effect on obesity, not only by modulating the redox state, but also due to their anti-inflammatory activity. Coffee, which is one of the most consumed beverages, is very rich in phenolic compounds. Bioavailability studies on coffee phenols have shown that the most abundant group of metabolites in plasma and urine are dihydrocaffeic (DHCA), dihydroferulic (DHFA), and hydroxyhippuric (HHA) acids, the three acids of colonic origin. To better understand the antioxidant and anti-inflammatory properties of DHCA, DHFA, and HHA, an inflammation/oxidation model was set up in the pre-adipocyte 3T3-L1 cell line using tumor necrosis factor-α (TNF-α). After the exposure of 3T3-L1 cells to 0.5, 1, 5, and 10 µM of TNF-α at different times, the cell viability, interleukin (IL)-6 secretion, and the production of reactive oxygen species (ROS) and glutathione (GSH) were determined. Using the TNF-α prooxidant and proinflammatory conditions established (10 µM, 24 h), it was observed that the physiological concentrations (0.5, 1, 5, and 10 µM) of DHCA, DHFA, and HHA induced dose-dependent antioxidant effects according to the ROS, GSH, and antioxidant enzyme (glutathione peroxidase) results. In addition, reductions in the IL-1β, IL-6, and monocyte chemoattractant protein-1 (MCP-1) concentrations were observed to different extents depending on the metabolite (DHFA, HHA, or DHCA) and the concentration used. In conclusion, the main colonic metabolites from coffee chlorogenic acids may counteract TNF-α-induced inflammation and oxidative stress in the 3T3-L1 cell line, and thus, they present antiobesity potential.

Effect of Ferulic Acid and Its Derivatives on Cold-Pressed Flaxseed Oil Oxidative Stability and Bioactive Compounds Retention during Oxidation

Ferulic acid (FA) is a naturally occurring phenolic antioxidant that is widely used in the food, pharmaceutical, and cosmetic industries due to its low toxicity. Its derivatives also find numerous industrial applications and may have even higher biological activity than ferulic acid. In this study, the effect of the addition of FA and its derivatives-including vanillic acid (VA), dihydroferulic acid (DHFA), and 4-vinylguaiacol (4-VG)-on the oxidative stability of cold-pressed flaxseed oil and the degradation of bioactive compounds during oxidation was investigated. The results showed that FA and its derivatives affected the oxidative stability of flaxseed oil, but their antioxidant activity depended on the concentration (25-200 mg/100 g oil) and temperature of treatment (60-110 °C). Based on Rancimat test results, flaxseed oil oxidative stability predicted at 20 °C increased linearly with ferulic acid concentration, while its derivatives effectively prolonged the induction time at lower concentrations (50-100 mg/100 g oil). The addition of phenolic antioxidants (80 mg/100 g) generally showed a protective effect against polyunsaturated fatty acids (DHFA and 4-VG), sterols (4-VG), tocols (DHFA), squalene, and carotenoids (FA). The exception was VA, which increased the degradation of most bioactive compounds. It is believed that adding properly composed mixtures of FA and its derivatives (DHFA and 4-VG) can extend the shelf life of flaxseed oil and provide nutritional benefits.