Hypocholesterolemic effect of quercetin-rich onion peel extract in C57BL/6J mice fed with high cholesterol diet

Protective effect of onion peel extract on ageing mouse oocytes

Mammalian oocytes not fertilized immediately after ovulation can undergo ageing and a rapid decline in quality. The addition of antioxidants can be an efficient approach to delaying the oocyte ageing process. Onion peel extract (OPE) contains quercetin and other flavonoids with natural antioxidant activities. In this study, we investigated the effect of OPE on mouse oocyte ageing and its mechanism of action. The oocytes were aged in vitro in M16 medium for 16 h after adding OPE at different concentrations (0, 50, 100, 200, and 500 μg/ml). The addition of 100 μg/ml OPE reduced the oocyte fragmentation rate, decreased the reactive oxygen species (ROS) level, increased the glutathione (GSH) level, and improved the mitochondrial membrane potential compared with the control group. The addition of OPE also increased the expression of SOD1, CAT, and GPX3 genes, and the caspase-3 activity in OPE-treated aged oocytes was significantly lower than that in untreated aged oocytes and similar to that in fresh oocytes. These results indicated that OPE delayed mouse oocyte ageing by reducing oxidative stress and apoptosis and enhancing mitochondrial function.

Potential Role of Quercetin Glycosides as Anti-Atherosclerotic Food-Derived Factors for Human Health

Quercetin is a monomeric polyphenol of plant origin that belongs to the flavonol-type flavonoid subclass. Extensive studies using cultured cells and experimental model animals have demonstrated the anti-atherosclerotic effects of dietary quercetin in relation to the prevention of cardiovascular disease (CVD). As quercetin is exclusively present in plant-based foods in the form of glycosides, this review focuses on the bioavailability and bioefficacy of quercetin glycosides in relation to vascular health effects. Some glucose-bound glycosides are absorbed from the small intestine after glucuronide/sulfate conjugation. Both conjugated metabolites and deconjugated quercetin aglycones formed by plasma β-glucuronidase activity act as food-derived anti-atherogenic factors by exerting antioxidant, anti-inflammatory, and plasma low-density lipoprotein cholesterol-lowering effects. However, most quercetin glycosides reach the large intestine, where they are subject to gut microbiota-dependent catabolism resulting in deglycosylated aglycone and chain-scission products. These catabolites also affect vascular health after transfer into the circulation. Furthermore, quercetin glycosides may improve gut microbiota profiles. A variety of human cohort studies and intervention studies support the idea that the intake of quercetin glycoside-rich plant foods such as onion helps to prevent CVD. Thus, quercetin glycoside-rich foods offer potential benefits in terms of cardiovascular health and possible clinical applications.

Anti-hypercholesterolemic activity of standardized fermented Allium cepa L. var aggregatum extract: In vitro and in vivo studies

Introduction: Allium cepa extract has been reported to have anti-hypercholesterolemic activity in rats. This study was conducted to investigate the effects of standardized fermented A. cepa L. var aggregatum extract on cholesterol levels and HMG-CoA reductase enzyme. Methods: The fermented A. cepa extract was standardized by the presence of quercetin using a validated high performance liquid chromatography (HPLC) method. The activity of the extract on HMG-CoA reductase was determined using HMG-CoA Assay kits, then measured by Nano spectrophotometry. In vivo study was conducted in hypercholesterolemic rats. The extract was administered orally at doses of 100, 200, and 300 mg/kg body weight (bw) to rats for 21 days and the cholesterol levels were measured every week. Results: All doses of fermented A. cepa extract and its marker compound, quercetin, ameliorated the levels of high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) as compared to those of negative control (P<0.05). Of all the doses, fermented A. cepa extract at the dose of 200 mg/kg bw displayed the highest reduction in LDL-C levels. In addition, the extract at the dose of 200 mg/kg bw showed the strongest enhancement in HDL-C levels. The fermented A. cepa extract and quercetin also inhibited the HMG-CoA reductase enzyme with inhibitory activity of 61.78%. Conclusion: The ethanol extract of fermented A. cepa shows anti-hypercholesterolemic activity. The strong anti-hypercholesterolemic activity of the extract might be due to the high amounts of quercetin, although other constituents may also contribute.

Onion (Allium cepa L.) peels: A review on bioactive compounds and biomedical activities

Huge quantities of byproducts/wastes generated in onion processing are usually discarded, but they are excellent sources of bioactive compounds and phytochemicals. However, with growing interest in the sustainable use of resources and the circular economy to reduce adverse impacts on the environment, food processing wastes such as onion peel/skin can be extracted and employed as inputs in developing or reformulating nutrient supplements, and pharmacological drugs. This review highlights major bioactive components, especially total phenolics, total flavonoid, quercetin and its derivatives present in onion peel/skin and their therapeutic applications as cardioprotective, neuroprotective, antiobesity, antidiabetic, anticancer and antimicrobial agents. The present review emphasized that onion peel is one of the important agricultural by-products which is rich in bioactive compounds and can be utilized as health promoting ingredient especially in pharmacological and biomedical fields. Thus, with increasing burden of life style disorders/non-communicable diseases, finding suitable natural alternative for their treatment is one major concern of the researchers and onion peel and its extract can be exploited as a prime ingredient.

Recent Advances in Bioactive Compounds, Health Functions, and Safety Concerns of Onion (Allium cepa L.)

Onion (Allium cepa L.) is a common vegetable, widely consumed all over the world. Onion contains diverse phytochemicals, including organosulfur compounds, phenolic compounds, polysaccharides, and saponins. The phenolic and sulfur-containing compounds, including onionin A, cysteine sulfoxides, quercetin, and quercetin glucosides, are the major bioactive constituents of onion. Accumulated studies have revealed that onion and its bioactive compounds possess various health functions, such as antioxidant, antimicrobial, anti-inflammatory, anti-obesity, anti-diabetic, anticancer, cardiovascular protective, neuroprotective, hepatorenal protective, respiratory protective, digestive system protective, reproductive protective, and immunomodulatory properties. Herein, the main bioactive compounds in onion are summarized, followed by intensively discussing its major health functions as well as relevant molecular mechanisms. Moreover, the potential safety concerns about onion contamination and the ways to mitigate these issues are also discussed. We hope that this paper can attract broader attention to onion and its bioactive compounds, which are promising ingredients in the development of functional foods and nutraceuticals for preventing and managing certain chronic diseases.

Therapeutic Potential of Quercetin to Alleviate Endothelial Dysfunction in Age-Related Cardiovascular Diseases

The vascular endothelium occupies a catalog of functions that contribute to the homeostasis of the cardiovascular system. It is a physically active barrier between circulating blood and tissue, a regulator of the vascular tone, a biochemical processor and a modulator of coagulation, inflammation, and immunity. Given these essential roles, it comes to no surprise that endothelial dysfunction is prodromal to chronic age-related diseases of the heart and arteries, globally termed cardiovascular diseases (CVD). An example would be ischemic heart disease (IHD), which is the main cause of death from CVD. We have made phenomenal advances in treating CVD, but the aging endothelium, as it senesces, always seems to out-run the benefits of medical and surgical therapies. Remarkably, many epidemiological studies have detected a correlation between a flavonoid-rich diet and a lower incidence of mortality from CVD. Quercetin, a member of the flavonoid class, is a natural compound ubiquitously found in various food sources such as fruits, vegetables, seeds, nuts, and wine. It has been reported to have a wide range of health promoting effects and has gained significant attention over the years. A growing body of evidence suggests quercetin could lower the risk of IHD by mitigating endothelial dysfunction and its risk factors, such as hypertension, atherosclerosis, accumulation of senescent endothelial cells, and endothelial-mesenchymal transition (EndoMT). In this review, we will explore these pathophysiological cascades and their interrelation with endothelial dysfunction. We will then present the scientific evidence to quercetin's anti-atherosclerotic, anti-hypertensive, senolytic, and anti-EndoMT effects. Finally, we will discuss the prospect for its clinical use in alleviating myocardial ischemic injuries in IHD.

Therapeutic Potential of Quercetin as an Antiatherosclerotic Agent in Atherosclerotic Cardiovascular Disease: A Review

Atherosclerotic cardiovascular disease (ASCVD) is one of the diseases with the highest morbidity and mortality globally. It causes a huge burden on families and caregivers and high costs for medicine and surgical interventions. Given expensive surgeries and failures of most conventional treatments, medical community tries to find a more cost-effective cure. Thus, attentions have been primarily focused on food or herbs. Quercetin (Qu) extracted from food, a flavonoid component, develops potentials of alternative or complementary medicine in atherosclerosis. Due to the wide range of health benefits, researchers have considered to apply Qu as a natural compound in therapy. This review is aimed to identify the antiatherosclerosis functions of Qu in treating ASCVD such as anti-inflammatory, antioxidant properties, effects on endothelium-dependent vasodilation, and blood lipid-lowering.

Nostoc sphaeroids Kütz ameliorates hyperlipidemia and maintains the intestinal barrier and gut microbiota composition of high-fat diet mice

Hyperlipidemia is associated with chronic inflammation and intestinal dysbiosis. The purpose of this study was to investigate the protective effect of Nostoc sphaeroids Kütz (NO) on diet-induced hyperlipidemia in mice. Experimental animals received a high-fat diet (HFD) for 4 weeks, then an HFD supplemented with 2.5% or 7.5% NO for 6 weeks. HFD-fed mice exhibited a significant increase in serum total cholesterol, triglycerides, and low-density lipid cholesterol, and a decrease in high-density lipid cholesterol. NO supplementation was associated with significantly lower dyslipidemia, decreased intestinal inflammation, and inhibition of toll-like receptor 4 gene repression in HFD-fed mice. Results suggest that NO treatment protected the integrity of the intestinal barrier. NO treatment was also associated with significant changes in the intestinal microbiota induced by HFD and an increase in the Firmicutes-to-Bacteroidetes ratio. Furthermore, NO treatment was also inversely correlated with mice obesity and hyperlipidemia NO and was associated with no significant in fecal short-chain fatty acids. In conclusion, NO significantly ameliorated hyperlipidemia induced by a HFD in mice, potentially via a decrease intestinal inflammation, increase in intestinal barrier integrity, and amelioration in the gut microbiota.

Nostoc sphaeroids Kütz powder ameliorates diet-induced hyperlipidemia in C57BL/6j mice

Background

Hypercholesterolemia is a disease associated with numerous health problems. Growing evidence indicates that hypercholesterolemia, hyperlipidemia is closely linked to chronic inflammation, which can lead to cardiovascular disease, fatty liver disease, and type 2 diabetes.

Objective

The purpose of this study was to investigate the protective effect of Nostoc sphaeroids Kütz (NO) on diet-induced hyperlipidemia in mice.

Design

At first, experimental animals received a high-fat diet (HFD) for 4 weeks, and then received a HFD supplemented with 2.5% or 7.5% NO for 6 weeks. In the current study, results show that treatment with NO decreases weight gain and liver index induced by HFD. In addition, the serum levels of TC, TG and LDL are significantly decreased in NO treatment groups.

Results

From the results of Oil Red staining and Hematoxylin and eosin staining (HE), treatment with NO significantly reduces liver lipid accumulation and protect liver structure. Further analysis reveals that NO has positive effects on liver lipid metabolism and inflammation, as showed by the lower protein expressions of FAS and SREBP-1, the lower concentrations of TNF-α, IL-1β, IL-6, and the lower gene expressions of TNF-α, IL-1β, IL-6 and NF-kB.

Conclusions

Our results indicate that NO may significantly ameliorate diet-induced hyperlipidemia, which is possibly associated with improving liver lipid metabolism and reducing chronic inflammation.

Onion Peel Extract Increases Erythrocyte Membrane n-3 Fatty Acids in Overweight and Obese Korean Subjects

The association between obesity and erythrocyte fatty acids (FAs) has been suggested; however, there have been no studies on the effects of onion peel extract (OPE) on the composition of erythrocyte FAs. This study aimed to investigate the effects of OPE on the composition of erythrocyte FAs in overweight and obese subjects. This was a randomized, double-blind, and placebo-controlled trial conducted in overweight and obese Korean subjects. The placebo and OPE groups were taking placebo capsule or OPE capsule twice per day for 12 weeks. Body composition and fat distribution were measured using dual-energy X-ray absorptiometry. The OPE group showed significantly reduced body weight, body mass index, body fat mass, and percentage of body fat mass. After 12 weeks, eicosapentaenoic acid and monounsaturated FAs of the placebo group were significantly lower at baseline. Consumption of OPE ameliorated the decreasing polyunsaturated n-3 polyunsaturated FA (PUFA) n-3 and increasing PUFA n-6, which prevented an increased n-6/n-3 ratio. The changes in arm fat percentage (ARFATP), trunk fat percentage, and total fat percentage (FATP) were negatively correlated with the change in PUFA n-3. In addition, increased erythrocyte docosahexaenoic acid was associated with decreased ARFATP and FATP. These results suggest that OPE has beneficial effects on obesity by regulating erythrocyte n-6/n-3 ratio and preventing fat accumulation in various body regions.