A 1H NMR Investigation of the Interaction between Phenolic Acids Found in Mango (Manguifera indica cv Ataulfo) and Papaya (Carica papaya cv Maradol) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) Free Radicals

Abstract

The benefits of phenolic acids on human health are very often ascribed to their potential to counteract free radicals to provide antioxidant protection. This potential has been attributed to their acidic chemical structure, which possesses hydroxyl groups in different positions. Phenolic acids can interact between themselves and exhibit an additive, antagonistic or synergistic effect. In this paper, we used 1H NMR to analyze the interactions and mechanisms that are present in major phenolic acids found in mango (gallic, protocatechuic, chlorogenic and vanillic acids) and papaya (caffeic, ferulic and p-coumaric acids), and the DPPH radical was used to evaluate the effect of the antioxidant mixtures. The interactions were found to occur via hydrogen bonds between the -OH and -COOH groups. Moreover, the phenolic acids exhibit two types of mechanisms for the neutralization of the DPPH radical. According to the results, these two mechanisms are Hydrogen Atom Transfer (HAT) and Single Electron Transfer (SET). The ability of the phenolic acid to neutralize the DPPH radical decreases in the following order in mango: gallic > chlorogenic > protocatechuic > vanillic. Moreover, within the acids found in papaya, the order was as follows: caffeic > p-coumaric > ferulic.

Antidiabetic activity‐guided isolation of gallic and protocatechuic acids fromHibiscus sabdariffacalyxes

“…This indicates that compounds I and II are the antidiabetic compounds in the EtOAc fraction of H. sabdariffa . H 1 and C 13 NMR data revealed that fractions I and II are protocatechuic acid and gallic acid, respectively (Figure ) (López‐Martínez, Santacruz‐Ortega, Navarro, Sotelo‐Mundo, & González‐Aguilar, ; Cen, Xiao, Chen, & Liu, ). Interestingly, earlier studies have also demonstrated the α‐amylase and α‐glucosidase inhibitory activities of these compounds (Oboh, Ogunsuyi, Ogunbadejo, & Adefegha, ).…”

One-Pot Water-Based Hydrophobic Surface Modification of Cellulose Nanocrystals Using Plant Polyphenols

“…In addition, the peaks from 3 to 5 ppm in TA-DA spectrum are attributed to the protons on amines adjacent to the aromatic rings, suggesting the reaction between TA-DA. 52 Lastly, the disappearance of phenol proton peaks from 9 to 10 pm in TA-DA spectrum suggests the oxidation of phenol groups to quinone groups. It should be noted that tannic acid was not oxidized beforehand in the NMR sample preparation (whereas it is in the reaction with CNCs), which implies the addition of decylamine further induces the oxidation of tannic acid.…”

New possibilities of use of oat raw materials for investigation of biologically active components in therapy of experimental diabetes

“…The bulk weight of dry chopped oat straw in these researches is (0,12±0,01) g/sm 3 on condition that the length of the used aggregates is 5 mm and aggregates are made by chopping the native raw materials on disagglomerator of rotary-cutting type. The calculation of the bulk weight was held in compliance with standard methods.…”

“…At the moment, a considerable number of scientifically-practical researches aimed at studying polyphenol component of numerous products of economic activity, such as wine [1], some agricultural products [2,3], and herbs, among which lists the oat, Avena Sativa, in its various natural and synthetic forms, are known. Polyphenols of the vegetative nature are represented by a variety of forms that potentially anticipates a wide range of non-specific and specific biological activity, and actualizes its further research and application in the medical practice [4,5].…”