1. Introduction
Nonalcoholic fatty liver disease (NAFLD) is a multifactorial disease, related to a complex living environment, heredity, and dietary habits. Patients with NAFLD have lower survival rates than healthy people of the same age and gender [
1]. High-calorie diets and continued inactivity contribute to weight gain and promote the development of NAFLD [
2]. Although the early stages of NAFLD may be reversible, studies have shown that 15% to 20% of patients with NAFLD can develop cirrhosis, and 30% to 40% of patients can suffer liver disease-related morbidity and mortality [
3]. Weight loss through improved diet and increased physical activity has been the cornerstone therapy of NAFLD. Recent therapies using functional foods and dietary supplements have been shown to be beneficial [
2,
3]. There is evidence of a link between oxidative stress and the presence of NAFLD and its progression, particularly related to mechanisms such as mitochondrial dysfunction, endoplasmic reticulum (ER) stress, iron metabolism derangements, insulin resistance, and endothelial dysfunction [
4,
5,
6].
The understanding of the molecular mechanisms responsible for lipid accumulation, oxidative balance impairment, and fibrosis in the liver could improve the therapeutic approach to decrease the risk of the disease progression. Antioxidant compounds, which modulate lipogenesis, inflammation, lipid oxidation and peroxidation, represent a new, attractive therapeutic approach for patients suffering from hepatic steatosis [
5,
7]. International recommendations for the treatment of nonalcoholic fatty liver suggest a reduction in the consumption of fats and sugars in the diet [
5]. Additionally, the use of antioxidant micronutrients has been suggested as a potential treatment alternative, since oxidative stress is also pivotal in the progression of NALFD [
7]. The Mediterranean diet, which is rich in antioxidant compounds such as polyphenols [
8,
9], has been shown to have a protective effect against this disease. Polyphenols are a heterogeneous group of compounds derived from plants. The hepatoprotective effects of some polyphenols have been reported, which modulate insulin resistance, oxidative stress, and inflammation [
9]. These researchers suggest that the hepatoprotector mechanism may be related to the enhancement of the antioxidant capacity of cells [
9,
10].
Several groups have outlined the potential bioactive roles for honeybee pollen including antioxidant, immunomodulatory, cardioprotective, antimicrobial, and anti-inflammatory activities [
11]. These activities are mainly attributed to phenolic compounds such as flavonoids. Poland bee pollen extract reduced and/or prevented the occurrence of steatosis and degenerative changes in the liver of mice caused by a high-fat diet, which may suggest a hepatoprotective role of bee pollen extract [
12]. However, another study using
Schisandra chinensis bee pollen on nonalcoholic fatty liver disease and gut microbiota in high-fat diet-induced obese mice suggested that phenolic compound present in the extract could attenuate the features of the metabolic syndrome [
13].
In order to provide new and healthy sources of important food components, human society has developed so-called “functional food” which can be defined as a food prepared in order to afford different compounds (i.e., vitamins, fatty acids, proteins, carbohydrates, polyphenols, carotenoids, etc.) with the ability to have a positive influence on health [
14]. The average content of polyphenols in pollen is around 1.6% (1.6 g/100 g) [
15], which defines it as an excellent source of these bioactive compounds [
14]. The botanical origin of pollen, its chemical composition, the amounts of major bioactive compounds such as polyphenols and carotenoids, and its antioxidant properties should be provided to better understand the impact of pollen addition in the formulation of functional food and feed products [
14].
The central zone of Chile is one of five regions in the world that has a Mediterranean climate and is the largest producer of bee pollen in the country. The Valparaiso region (V region) is located in this area, which is covered by native vegetation characterized by a high level of endemism and biodiversity. Beehives are usually located in the “matorral” (the scrubs) communities, shrubby sclerophyllous vegetation that covers the slopes of the coastal range in the semiarid Mediterranean zone [
16]. Our preliminary studies about chemical composition of bee pollen from the central zone of Chile showed the strong presence of phenolic compounds such as syringic acid, coumaric acid, myricetin, and quercetin [
16].
The purpose of this study was to characterize according to botanical origin, phenolic profile, quercetin concentration, and antioxidant activity the honeybee pollen extracts from the central zone of Chile. From the characterized honeybee pollen extracts we selected six pollen samples with different concentrations of total phenols and we tested their ability to reverse steatosis in an in vitro cell model of liver steatosis.