Long chain fatty acid acylated derivatives of quercetin-3-o-glucoside as antioxidants to prevent lipid oxidation

Investigating the effects of quercetin fatty acid esters on apoptosis, mechanical properties, and expression of ERK in melanoma cell line (A375)

AIMS

Malignant melanoma (MM) is the most fatal skin cancer with a critical increase in the number of cases in the last decades. Recent studies have shown the antitumor potential of active biological phytochemical structures of flavonoids for the prevention and treatment of cancerous cells. In this study, two quercetin fatty acid esters (α-linolenic acid (ALA) and linoleic acid (LA)) compounds were evaluated in terms of inducing apoptotic human melanoma cells (A375) death in vitro.

MAIN METHODS

The MTT assay was utilized for comparing the effects of quercetin, ALA, and LA on A375 cell viability concentrations of 5, 25, 35, 50, and 100μg/mL for 24 and 48 h to obtain IC50. To detect the effects on apoptosis and to determine p-ERK/ERK apoptosis-related signaling pathway proteins level, flow-cytometry and western blot were used. Finally, the nano-mechanical properties of the melanoma A375 membrane structure containing elastic modulus value and cell-cell adhesion forces were investigated using Atomic Force Microscopy (AFM). Statistical data was analyzed in GraphPad v.8.0.0.

KEY FINDINGS

The most significant A375 cell viability amplified effect of Q-LA was observed with a half-maximal inhibitory concentration (IC50 = 35 μg/ml, 48 h), proportional to dose. Ester compounds, especially Q-LA, showed the highest cell proliferation inhibition with improved elastic modulus, cell-cell adhesion forces (253 ± 11.2), and elevated apoptosis-inducing effect (p < 0.01**). Moreover, Q-LA significantly decreased the mean levels of p-ERK phosphorylation (0.1439) and, subsequently, apoptosis in A375 cells.

SIGNIFICANCE

The data presented in this study confirmed the antitumor activity of ester compounds against A375 cells, high-lighting the ability of the tested compounds to induce apoptosis.

Rutin bioconjugates as potential nutraceutical prodrugs: An in vitro and in ovo toxicological screening

Rutin (RUT) is considered one the most attractive flavonoids from a therapeutic perspective due to its multispectral pharmacological activities including antiradical, anti-inflammatory, antiproliferative, and antimetastatic among others. Still, this compound presents a low bioavailability what narrows its clinical applications. To overcome this inconvenience, the current paper was focused on the synthesis, characterization, and toxicological assessment of two RUT bioconjugates obtained by enzymatic esterification with oleic acid (OA) and linoleic acid (LA)—rutin oleate (RUT-O) and rutin linoleate (RUT-L), as flavonoid precursors with improved physicochemical and biological properties. Following the enzymatic synthesis in the presence of Novozyme® 435, the two bioconjugates were obtained, their formation being confirmed by RAMAN and FT-IR spectroscopy. The in vitro and in ovo toxicological assessment of RUT bioconjugates (1–100 µM) was performed using 2D consecrated cell lines (cardiomyoblasts - H9c2(2-1), hepatocytes—HepaRG, and keratinocytes—HaCaT), 3D reconstructed human epidermis tissue (EpiDerm™), and chick chorioallantoic membranes, respectively. The results obtained were test compound, concentration—and cell-type dependent, as follows: RUT-O reduced the viability of H9c2(2-1), HepaRG, and HaCaT cells at 100 µM (to 77.53%, 83.17%, and 78.32%, respectively), and induced cell rounding and floating, as well as apoptotic-like features in the nuclei of all cell lines, whereas RUT-L exerted no signs of cytotoxicity in all cell lines in terms of cell viability, morphology, and nuclear integrity. Both RUT esters impaired the migration of HepaRG cells (at 25 µM) and lack irritative potential (at 100 µM) in vitro (tissue viability >50%) and in ovo (irritation scores of 0.70 for RUT-O, and 0.49 for RUT-L, respectively). Computational predictions revealed an increased lipophilicity, and reduced solubility, drug-likeness and drug score of RUT-O and RUT-L compared to their parent compounds—RUT, OA, and LA. In conclusion, we report a favorable toxicological profile for RUT-L, while RUT-O is dosage-limited since at high concentrations were noticed cytotoxic effects.

Fatty Acid Hydroxytyrosyl Esters of Olive Oils Are Bioaccessible According to Simulated In Vitro Gastrointestinal Digestion: Unraveling the Role of Digestive Enzymes on Their Stability

Recently, new bioactive compounds were identified in olive oil, lipophenols, which are composed of a fatty acid (FA) and a phenolic core, such as HT (HT-FA). However, their bioaccessibility remains unknown. Thus, the present study uncovers the impact of the separate phases of gastrointestinal digestion on the release and stability of HT-FAs from oily matrices under in vitro simulated conditions. Accordingly, it was found that the bioaccessibility of HT derivatives is largely dependent on the type of FA that esterifies HT, as well as the food matrix. Also, the generation of HT-FAs during intestinal digestion was observed, with pancreatin being the enzyme responsible, to a higher extent, for the de novo formation of lipophenolic derivatives. These findings prompt us to identify new applications to oily matrices and their byproducts as potential functional ingredients for the promotion of health, where the possible formation of new lipophenols during digestion should be taken into consideration.

Biocatalytic Approaches for an Efficient and Sustainable Preparation of Polyphenols and Their Derivatives

Many sectors of industry, such as food, cosmetics, nutraceuticals, and pharmaceuticals, have increased their interest in polyphenols due to their beneficial properties. These molecules are widely found in Nature (plants) and can be obtained through direct extraction from vegetable matrices. Polyphenols introduced through the diet may be metabolized in the human body via different biotransformations leading to compounds having different bioactivities. In this context, enzyme-catalyzed reactions are the most suitable approach to produce modified polyphenols that not only can be studied for their bioactivity but also can be labeled as green, natural products. This review aims to give an overview of the potential of biocatalysis as a powerful tool for the modification of polyphenols to enhance their bioaccessibility, bioavailability, biological activity or modification of their physicochemical properties. The main polyphenol transformations occurring during their metabolism in the human body have been also presented.

The effects of the esterified Quercetin with omega3 and omega6 fatty acids on viability, nanomechanical properties, and BAX/BCL-2 gene expression in MCF-7 cells

Quercetin is one of the major flavonoids and it appears to have cytotoxic effects on various cancer cells through regulating the apoptosis pathway genes such as BAX and BCL2. Combination of Quercetin (Q) with other compounds can increase its effectiveness. In the present study, the effects of the Quercetin and its esterified derivatives on viability, nanomechanical properties of cells, and BAX/BCL-2 gene expression were investigated. Using the MTT and flow cytometry assays, the cytotoxic potential, apoptosis, and necrosis were investigated. The AFM assay was performed to find the nanomechanical properties of cells as the elastic modulus value and cellular adhesion forces. The BAX/BCL2 gene expression was investigated through the Real-Time PCR. The results showed that the esterification of Quercetin with linoleic acid (Q-LA) and α-linolenic acid (Q-ALA) increased the cytotoxic potential of Q. The elastic modulus value and cellular adhesion forces were increased using the esterified derivatives and the highest ratio of BAX/BCL2 gene expression was observed in Q-LA. Esterified Quercetin derivatives have a higher cytotoxic effect than the un-esterified form in a dose-dependent manner. Esterified derivatives caused the nanomechanical changes and pores formation on the cytoplasmic membrane. One of the internal apoptosis pathway regulation mechanisms of these compounds is increasing the BAX/BCL2 gene expression ratio.

Physicochemical Changes of Deep-Fat-Fried Chicken Drumsticks Treated with Quercetin-in-Edible Coating during Storage Time

In this study, 10% of chicken protein isolate (CPI) and quercetin (1 mg/mL) were used to develop an edible coating to improve the oxidative stability of deep-fat-fried chicken drumsticks during refrigerated storage (4 °C) for 10 days. Chicken samples with edible coating formulated with only 10% CPI served as the control. Although the thiobarbituric acid reactive substances (TBARS) values of the treated samples were lower than the control samples, no significant differences were observed. Quercetin-treated samples were generally harder than control samples. The pH was reduced by quercetin incorporation (p < 0.05). L* and b* values increased, while there was no significant variation in a* values during storage (p > 0.05).

Lipase-catalysed synthesis of mono- and di-acyl esters of glyceryl caffeate in propylene carbonate and their antioxidant properties in tuna oil

Development of new non-toxic antioxidants with diverse hydrophobic properties is important due to growing concerns about the toxicity of artificial oil-soluble antioxidants, the comparatively low effectiveness of natural options, and the complex role hydrophobicity plays in antioxidant effectiveness. Using caffeic acid, a naturally occurring phenolic acid with potent antioxidant activity, a range of glyceryl caffeate esters (decanoate and palmitate) were prepared using lipase-catalysed esterification reactions. Glyceryl-1-caffeate (GC) was prepared from ethyl caffeate and glycerol (acting as both the solvent and the substrate), catalysed by immobilised Candida Antarctica lipase B (Novozym-435) at 80 °C under vacuum. Esterification of GC with decanoic acid using immobilised Thermomyces lanuginosus lipase (TLIM) or Novozym-435 was found to be selective towards mono-acylated or di-acylated products, respectively. The reaction was performed in an unconventional solvent, propylene carbonate (PC), which has many of the attributes of a green solvent. Product conversions in PC were comparable to the best performing conventional solvents. In contrast to conventional volatile solvents, the low volatility of PC allowed the reaction to be performed under vacuum, without the need for molecular sieves for removal of water produced during the reaction. Diisopropyl ether was effective at extracting the more lipophilic products from PC. Both the lipase (Novozym-435) and PC were reused four times with only a small loss in conversion efficiency. Glyceryl caffeate esters performed much better than α-tocopherol at protecting bulk tuna oil from oxidation (analysed using Rancimat). A comparison of glyceryl caffeate esters (decanoate/palmitate and mono-/di-acylated) showed that their antioxidant effectiveness in bulk tuna oil was not affected by chain-length, but compounds containing only one fatty ester were slightly more effective than those containing two fatty esters.

Polydatin-fatty acid conjugates are effective antioxidants for stabilizing omega 3-containing bulk fish oil and fish oil emulsions

Candida antarctica lipase B-catalysed synthesis of lipophilic esters of polydatin was investigated along with their antioxidant activities. The effects of synthesis parameters such as solvent, substrate molar ratio, enzyme concentration, addition of molecular sieves, reaction temperature and time on the production of ester were studied and optimised. The highest production of esters was obtained with acetone as the reaction solvent. The antioxidant activities of the esters were compared with those of commercial butylated hydroxytoluene (BHT) and α-tocopherol. All polydatin esters inhibited the oxidative destruction of β-carotene more effectively than did BHT and α-tocopherol. Results of thiobarbituric acid tests showed that in bulk fish oil, all esters were more effective than α-tocopherol at 2 mmol/kg concentration but were not as effective as BHT. In fish oil-emulsions, all esters were more effective than both BHT and α-tocopherol at 2 mmol/kg concentration. The synthesized polydatin esters are promising antioxidants for oil/fat-based foods.

The effects of polyphenols and other bioactives on human health

Although deficiencies in polyphenol intake do not result in specific deficiency diseases, adequate intake of polyphenols could confer health benefits, especially with regard to chronic diseases. Tea, cocoa, fruits, and berries, as well as vegetables, are rich in polyphenols. Flavan-3-ols from cocoa have been found to be associated with a reduced risk of stroke, myocardial infarction, and diabetes, as well as improvements in lipids, endothelial-dependent blood flow and blood pressure, insulin resistance, and systemic inflammation. The flavonoid quercetin and the stilbene resveratrol have also been associated with cardiometabolic health. Although polyphenols have been associated with improved cerebral blood flow, evidence of an impact on cognition is more limited. The ability of dietary polyphenols to produce clinical effects may be due, at least in part, to a bi-directional relationship with the gut microbiota. Polyphenols can impact the composition of the gut microbiota (which are independently associated with health benefits), and gut bacteria metabolize polyphenols into bioactive compounds that produce clinical benefits. Another critical interaction is that of polyphenols with other phytochemicals, which could be relevant to interpreting the health parameter effects of polyphenols assayed as purified extracts, whole foods, or whole food extracts.

Lipase-Produced Hydroxytyrosyl Eicosapentaenoate is an Excellent Antioxidant for the Stabilization of Omega-3 Bulk Oils, Emulsions and Microcapsules

In this study, several lipophilic hydroxytyrosyl esters were prepared enzymatically using immobilized lipase from Candida antarctica B. Oxidation tests showed that these conjugates are excellent antioxidants in lipid-based matrices, with hydroxytyrosyl eicosapentaenoate showing the highest antioxidant activity. Hydroxytyrosyl eicosapentaenoate effectively stabilized bulk fish oil, fish-oil-in-water emulsions and microencapsulated fish oil. The stabilizing effect of this antioxidant may either be because it orients itself with the omega-3 fatty acids in the oil, thereby protecting them against oxidation, or because this unstable fatty acid can preferentially oxidise, thus providing an additional mechanism of antioxidant protection. Hydroxytyrosyl eicosapentaenoate itself was stable for one year when stored at -20 °C.

Epigallocatechin Gallate: A Review of Its Beneficial Properties to Prevent Metabolic Syndrome

Obesity and being overweight are linked with a cluster of metabolic and vascular disorders that have been termed the metabolic syndrome. This syndrome promotes the incidence of cardiovascular diseases that are an important public health problem because they represent a major cause of death worldwide. Whereas there is not a universally-accepted set of diagnostic criteria, most expert groups agree that this syndrome is defined by an endothelial dysfunction, an impaired insulin sensitivity and hyperglycemia, dyslipidemia, abdominal obesity and hypertension. Epidemiological studies suggest that the beneficial cardiovascular health effects of diets rich in green tea are, in part, mediated by their flavonoid content, with particular benefits provided by members of this family such as epigallocatechin gallate (EGCG). Although their bioavailability is discussed, various studies suggest that EGCG modulates cellular and molecular mechanisms of various symptoms leading to metabolic syndrome. Therefore, according to in vitro and in vivo model data, this review attempts to increase our understanding about the beneficial properties of EGCG to prevent metabolic syndrome.