Elsevier

Journal of Functional Foods

Volume 27, December 2016, Pages 461-471
Journal of Functional Foods

Dietary potato peel extract reduces the toxicity of cholesterol oxidation products in rats

https://doi.org/10.1016/j.jff.2016.09.019Get rights and content

Highlights

  • Cholesterol oxidation products are found in many processed foods.

  • Potato peel extract is a source of bioactive components in foods.

  • Potato peel extract decreases cholesterol oxidation products in rats.

  • Potato peel extract increases antioxidant enzymes activities in rats.

  • Caffeic acid and chlorogenic acid are predominant components in potato peel extract.

Abstract

We determined the polyphenolic profiles of the potato peel by HPLC. To elucidate the effect of potato peel extract (PPE) on the toxicity of cholesterol oxidation products (COPs) in rats, a synthetic polyphenolic mixture was prepared, mimicking the composition of PPE. Six groups were treated with a control diet, an oxidized cholesterol diet, a PPE diet, an oxidized cholesterol plus PPE diet, and various doses (1–3%) of the PPE diet. After treatment, significantly increased liver glutathione and trolox equivalent antioxidant capacity levels; superoxide dismutase, catalase, and glutathione peroxidase activities; and mRNA expression were observed in the rats treated with 2% and 3% doses of the PPE diet and significantly decreased aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, blood urea nitrogen, creatinine, and COPs levels were observed compared with the control rats. These results demonstrated the PPE diet reduction in the long-term toxicity of COPs was significant in rats.

Introduction

Cholesterol oxidation products (COPs) from food are a disease-related concern. A variety of COPs have been detected in processed foods, such as meat products (Broncano, Petrón, Parra, & Timón, 2009), dairy products (Sieber, 2005) and seafood (Nikoo & Benjakul, 2015). Therefore, the consumption of COPs is inevitable in our usual diet. COPs have been known to have a more deleterious effect on arterial cells than pure cholesterol and are also more directly connected to negative biological effects and the development of certain cancers, oxidative DNA damage, mutagenesis, atherosclerosis and coronary heart disease (Hur, Lee, & Lee, 2015). Antioxidants have beenreported to prevent the oxidative damage caused by free radicals, thereby reducing arthritis, cardiovascular diseases, and the risk of cancer (Ayoub et al, 2016, Shahidi, Zhong, 2010) to inhibit lipid oxidation in biological systems (Barriuso et al, 2015, Shahidi, Wanasundara, 1992) and to impede degenerative diseases (Falowo et al, 2014, Shahidi, 1997).

High vegetable and fruit intake lowered the risk of cerebrovascular disease, which is partially because these foods have high flavonoid and phenolic acid contents (Juániz et al., 2016). Natural phenols from the plant kingdom work against DNA damage, lipid peroxidation, inflammation, hyperlipidemia and hypertension, and these beneficial effects have been frequently discussed (Liu et al., 2012). The potato peel, a waste byproduct from potato processing, could be considered a new source of natural antioxidants. Potato peels contain a number of antioxidant compounds that can effectively scavenge various reactive oxygen species/free radicals under in vitro conditions (Albishi, John, Al-Khalifa, & Shahidi, 2013a). Potato peel contains phenolic acids and sources of various classes of phenolic compounds, which include flavonoids; phenolic acids such as flavononols, flavonols, flavones, isoflavones, and flavans; amino phenolic compounds; and simple phenolics, coumarins, stilbenes, lignins, lignans, and tannins (Naczk & Shahidi, 2006). Recently, the antioxidant activity of potato peel extracts was evident from in vitro studies in food systems (Al-Weshahy, El-Nokety, Bakhete, & Rao, 2011). Moreover, as apple peel phenolics have a strong inhibitory effect on fish oil oxidation (Sekhon-Loodu, Warnakulasuriya, Rupasinghe, & Shahidi, 2013), the phenolic compounds of some edible plants are regarded as powerful antioxidants (Shahidi, Wanasundara, 1992, Wettasinghe et al, 2000). Antioxidants, flavonoids, and other phenolic compounds prevent or control the formation of free radicals with deleterious health effects and are therefore important in disease risk reduction, thereby augmenting the body's natural resistance to oxidative damage (Shahidi, 2000). The phenolic compounds in potatoes can be present in both soluble (free and soluble esters and soluble glycosides) and insoluble bound forms. These compounds are mostly substituted derivatives of hydroxycinnamic acid in the free form and hydroxybenzoic acid in the bound form (Shahidi, 2000, Shahidi, Naczk, 1995). Many studies have examined the enhanced antioxidative potential of insoluble bound phenolic compounds compared with soluble phenolics (Alasalvar et al, 2009, Liyana-Pathirana, Shahidi, 2006a, Shahidi, Wanasundara, 1992). In this context, the first part of this study was an investigation of the polyphenolic profile of potato peels. The in vivo, long-term toxicity of COPs in the presence of a synthetic phenolic acid and flavonoid mixture, mimicking the composition of PPE, was also examined in rats.

Section snippets

Manufacture of oxidized cholesterol

Cholesterol (Sigma-Aldrich Co., St. Louis, MO, USA) was heated at 180 °C for 18 h to produce oxidized cholesterol, with a peroxide value (POV) of approximately 56.3 meq/kg oil, a thiobarbituric acid-reactive substances (TBARS) content of 3.21 mg/kg oil, and an acid value (AV) of 2.95 mg/g oil. The POV, AV, and TBARS value in the oil were determined by the AOAC method.

Determination of total phenolic acid content

The total phenolic acid content was analyzed by the Folin–Ciocalteu method. The samples were centrifuged at 5000 × g for 15 min

Results

The phenolic acid and flavonoid content of PPE was determined and is shown in Table 1. The phenolic acid content (in GAE) of PPE was 86.3 mg/100 g, which was higher than the flavonoid content of PPE (27.5 mg/100 g). In an HPLC analysis, caffeic acid, p-coumaric acid, chlorogenic acid, and ferulic acid were present in higher amounts than the other components of PPE.

The effects of toxicity on oxidized cholesterol at different doses of the PPE supplementation on the expression of mRNA of CAT,

Discussion

The present in vivo study demonstrated that the administration of polyphenols have significant health benefits in humans. The biological properties attributed to polyphenols depend on the compounds' bioavailability. Although it is generally thought that the bioavailability of these compounds is rather low, studies have shown that the intestinal absorption of polyphenols can be high (Singh, Karnath, Narasirnharnurthy, & Rajini, 2008). Direct evidence of the bioavailability of phenolic compounds

Acknowledgment

This study was supported by Ministry of Science and Technology (MOST 105-2320-B-468-002-).

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