Nuts as functional foods: Variation of nutritional and phytochemical profiles and their in vitro bioactive properties

The aim of the present study was to examine the nutritional (fat, fatty acids, minerals, sugars) and bioactive compounds (polyphenols, tocochromanols, triterpene) and their influence on in vitro anti-diabetic (pancreatic α-amylase and intestinal α-glucosidase), anti-obesity (pancreatic lipase) and anti-cholinergic (AChE and BuChE) inhibitory activity of 8 different popular nuts-pecan, pine, hazelnuts, pistachio, almonds, cashew, walnuts, and macadamia. The total content of phenolic compounds in nuts ranged from 432.9 (walnuts) to 5.9 (pistachio) mg/100 g. The dominant polyphenols are polymeric procyanidins (walnuts - 415.1 mg/100 g). Nuts are rich in tocochromanols (832.9-4377.5 μg/100 g), especially α- and γ-tocopherols. The highest content of α-tocopherol (vitamin E) was detected in hazelnuts and almonds (2551.0 and 2489.7 μg/100 g, respectively) while the lowest amounts were detected in macadamia, cashew and walnuts. The most abundant in nuts are oleanic and pomolic acids (35 and 22 % of total, respectively), while betulin, uvaol and erythrodiol are less characteristic triterpenes for nuts (<1%). Pine nuts are the nuts with the highest content of triterpene (690.3 mg/100 g). Pistachio and almonds are the richest in total fat (>45 %), but monounsaturated (17.5-79.3 %; hazelnuts, almonds, cashew, macadamia, pistachio and pecan) and polyunsaturated (7.5-69.3 %; pine, walnuts) are the dominant fatty acids. Moreover, nuts are low in Cu, Zn, Mn and Na content, but rich in K (464.5-1772.3 mg/100 g) and Mg (197.0-502.5 mg/100 g). Macadamia, walnuts and cashew are good sources of Se. Pistachio, almonds and cashew were characterized by the highest content of sugars, but the dominant sugar was saccharose (58.2-2399.3 mg/100 g). All nuts showed high activity in inhibiting intestinal α-glucosidase (>90 %), but lower ability to inhibit pancreatic α-amylase and pancreatic lipase activity. The activity in inhibiting acetyl- and butylcholinesterase was up to 30 %. As described above, all nuts contain various compounds that improve the nutritional value. Therefore they should be one of the important components of the daily human diet rich in functional foods.