Sara Arranz

Comparison between free radical scavenging capacity and oxidative stability of nut oils

Several works have measured free radical scavenging capacity of nut oils, since they may become a significant source of dietary fat. However, they have not considered kinetic parameters, what was the first aim of this work. Also, it was studied the possible relation between values of free radical scavenging capacity DPPH and oxidative stability (Rancimat method) in different nut (hazelnut, peanut, pistachio, walnut and almond) oils. The ranking of antioxidant capacity of nut oils, by both assays, was: pistachio>hazelnut>walnut>almond>peanut. A significant correlation was found between DPPH and Rancimat methods assays. Tocopherols appear to be the responsible compounds of this antioxidant capacity being neglictible the contribution of polyphenols. An interference effect of phospholipids, present in methanolic fraction of nut oils, was observed in the determination of polyphenols in nut oils by Folin and ortho-diphenols assays.

High contents of nonextractable polyphenols in fruits suggest that polyphenol contents of plant foods have been underestimated.

The content of polyphenols in fruits reported in the literature normally refers to extractable polyphenols (EPP) analyzed in aqueous-organic extracts. However, significant amounts of bioactive compounds that are usually not considered in nutritional studies remain in the residue from extraction as nonextractable polyphenols (NEPP). The main objective of this work was to analyze both EPP and NEPP (hydrolyzable polyphenols and proanthocyanidins). EPP were analyzed in methanol/acetone/water extracts, and NEPP were determined in acidic hydrolysates of extraction residue from apple, peach, and nectarine using HPLC-MS and spectrophotometry. Results showed that the NEPP content (112-126 mg/100 g of fresh fruit) was higher than the EPP content (18.8-28 mg/100 g of fresh fruit). Further analyses of NEPP in other fruits and plant foods consumed in diets are needed to compile a complete database of use for nutritional and biological studies.

Bioavailability of Phenolic Antioxidants Associated with Dietary Fiber: Plasma Antioxidant Capacity After Acute and Long-Term Intake in Humans

Most studies on bioavailability of phenolic antioxidants are focused in foods and beverages in which they may be easily released from the food matrix, reaching a peak in plasma antioxidant capacity 1–2xa0h after the intake. However, plant foods contain significant amounts of polyphenols associated with dietary fiber. The aim of the present work was to seek the bioavailability of total phenolic antioxidants associated with dietary fiber by measuring plasma antioxidant capacity in human volunteers. An acute intake of 15xa0g of a dietary fiber rich in associated phenolic antioxidants in healthy volunteers (nu2009=u200910) increased antioxidant capacity of plasma in relation to a control group (nu2009=u20094), becoming significant 8xa0h after the intake. This shows that phenolic antioxidants associated with dietary fiber are at least partially bioavailable in humans, although dietary fiber appears to delay their absorption. No significant changes were observed after long-term intake (16xa0weeks, 34 subjects).

Nonextractable polyphenols, usually ignored, are the major part of dietary polyphenols: A study on the Spanish diet

SCOPEnDietary polyphenols (PP) can be divided into two groups: extractable polyphenols (EPP) or compounds solubilized by aqueous organic solvents, and nonextractable polyphenols (NEPP) or compounds that remain in their corresponding extraction residues. Most studies on food polyphenols and dietary intakes address exclusively EPP. The objective of this work was to determine the actual amount of PP, including NEPP, in food and in a whole diet.nnnMETHODS AND RESULTSnHPLC-MS analyses were performed to identify EPP in methanol-acetone extracts and NEPP in the acidic hydrolyzates of their extraction residues in cereals, fruits, vegetables, nuts, and legumes. NEPP contents, estimated as hydrolyzable PP plus nonextractable proanthocyanidins (PA), ranged from 880 mg/100 g dry weight in fruits to 210 mg/100 g in cereals and were substantially higher than the contents of EPP. NEPP intake (day/person) in the Spanish diet (942 mg) is higher than EPP intake (258 mg) fruits and vegetables (746 mg) are the major contributors to the total PP intake (1201 mg).nnnCONCLUSIONnNon extractable polyphenols are the major part of dietary polyphenols. The knowledge of intakes and physiological properties of NEPP may be useful for a better understanding of the potential health effects of dietary PP.