Basic nutritional investigationBioaccessibility of pistachio polyphenols, xanthophylls, and tocopherols during simulated human digestion
Introduction
Epidemiologic and clinical studies have demonstrated that nut consumption decreases the risk of cardiovascular disease: when subjects consumed test diets including mixed nuts, a 25% greater cholesterol-lowering response was found and this effect was attributed to the large proportion of unsaturated fatty acids present in nuts [1], [2]. The results of three almond (50–100 g/d), two peanut (35–68 g/d), one pecan nut (72 g/d), and four walnut (40–84 g/d) studies have demonstrated a decrease in total cholesterol (2–16%) and low-density lipoprotein (LDL) cholesterol (2–19%) compared with control subjects [3]. For pistachios in particular, recent publications have shown beneficial effects on cardiovascular disease risk factors, lipid parameters, endothelial function, inflammation, and oxidative status [4], [5]. In a randomized cross-over controlled feeding study, the inclusion of pistachios decreased total cholesterol, LDL cholesterol, non–high-density lipoprotein cholesterol, and plasma stearoyl-coenzyme A desaturase activity in a dose-dependent manner [4]. When pistachios were given to 32 normolipidemic healthy young men for 4 wk, significant decreases in blood glucose, total cholesterol, and serum interleukin-6 were observed, with improved endothelium vasodilation and total antioxidant status [5]. The consumption of pistachio nuts has been shown to significantly decrease oxidative stress, improving total cholesterol and its LDL levels in healthy volunteers [6]. Li et al. [7] showed pistachio consumption decreased plasma triacylglycerols and body weight when compared with a carbohydrate snack in obese subjects. Compared with other tree nuts, pistachios are very rich in phytosterols, potassium, vitamin B6, carotenoids, and tocopherols [8], [9] and have been ranked among the 50 foods highest in antioxidants [10]. Extensive in vivo and in vitro experiments on the effect of phenolic compounds have shown beneficial health activities as protective agents against cancer and cardiovascular, inflammatory, and aging disorders, and human pathogens [11], [12], [13]. Catechins have been shown to be particularly effective in cardiovascular disease prevention and in decreasing the oxidation of LDL [14].
A major challenge in evaluating the role of individual health-promoting components in the pistachio is the lack of information on their behavior in the gastrointestinal (GI) tract and in particular on factors that influence their bioavailability. A component of bioavailability is bioaccessibility, which is defined as the relative amounts of nutrients or phytochemicals “released” from a complex food matrix in the lumen of the GI tract, and therefore could potentially be available for absorption into the body [15]. This process is highly dependent on the physical and chemical properties of the food matrix and the way these change during digestion [16]. The choice of food matrix is therefore crucial for testing the bioaccessibility of several compounds under simulated GI digestion. We recently showed that cell walls play a crucial role in regulating nutrient bioaccessibility from almonds and that polyphenols from almond skin are potentially available for absorption during digestion [15], [17].
In this study, we characterized the polyphenols, carotenoids, and tocopherols in raw pistachios and roasted, salted pistachios and investigated their release during simulated human digestion in the gut. A dynamic gastric model of digestion that provides a realistic and predictive simulation of the physical and chemical processing and accurately mimics the transit time and the luminal environment within the human stomach was used for the digestion studies [18], [19], together with a duodenal simulated digestion.
To assess the effect of the food matrix, muffins containing raw pistachios were used to investigate the bioaccessibility of polyphenols, xanthophylls, and tocopherols.
Section snippets
Pistachios
Natural, raw, shelled pistachios (NPs; Pistacia vera L.) and roasted salted pistachio (RP) kernels (P. vera L.) from California were kindly provided by the American Pistachio Growers (Fresno, CA, USA). Home-made muffins containing NPs were prepared using the following ingredients: sugar (sucrose 178 g), butter at room temperature (118 g), eggs (two standard eggs), full-fat plain yogurt (240 g), white flour (470 g), baking soda (5 g), salt (1.2 g), and NPs (112 g). Each cooked muffin weighed 70
Flavonoids and phenolic acids in pistachios and pistachio muffins
Typical chromatograms of the polyphenols detected in the NPs and RPs are shown in Figure 1. Eleven flavonoids (flavanols, flavonols, and flavanones) and phenolic acids were identified (Table 1). The ultraviolet spectra of the different compounds were recorded from 200 to 380 nm and quantified at 270 nm.
As previously described [23], the major compounds identified in the pistachio samples were gallic acid, (+)-catechin, and isoquercetin. Hydroxybenzoic acids (as gallic and protocatechuic acids)
Discussion
The results presented in this work demonstrate that polyphenols, tocopherols, and lutein in pistachios are bioaccessible during simulated human gastric digestion and therefore available for absorption in the upper GI tract. Phenolic acids such as gallic and chlorogenic acids are generally absorbed in the upper GI tract within 1 to 2 h after their intake [25].
Polyphenols have been shown to have higher antioxidant capacity in vitro compared with vitamins and carotenoids and they represent the
Conclusion
We have demonstrated that bioactives from pistachios become rapidly accessible in the stomach, maximizing the possibility of absorption in the upper small intestine, which would contribute to the beneficial relation between pistachio consumption and health-related outcomes. Further human clinical studies are needed to validate the in vitro findings on the release of bioactives from pistachios.
Acknowledgments
The authors acknowledge the American Pistachio Growers and Setton Farms for providing the samples.
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Cited by (0)
This work was funded by the American Pistachio Growers (Fresno, CA, USA).