Estimation of phenolic compounds and antioxidant capacity in leaves of fruit species using near-infrared spectroscopy and a chemometric approach

Audrey Pissard,Darly Rodrigues Pompeu,Hervé Rogez,Marc Lateur,Pascal Dupont,Vincent Baeten

doi:10.25518/1780-4507.19000

Abstract

Description of the subject. Phenolic compounds are very important to the antioxidant capacity of plant species. Phenolic compounds and hence antioxidant capacity are commonly measured in the laboratory using indirect methods that involve several stages and chemicals. Objectives. This study aims to identify species with high content of phenolic compounds and antioxidant capacity and to measure these parameters in the leaves of fruit species using near-infrared spectroscopy (NIRS). Method. A total of 68 samples of different varieties of Prunus avium, Prunus cerasus, Malus domestica, Prunus domestica, Pyrus communis, Vitis vinifera, Ficus carica and Corylus avellana were investigated. The dried ground leaves were scanned in reflectance mode and the phenolic compound content (total phenolic compounds, total flavanols and total flavonols) and antioxidant capacity (2-2-diphenyl-1-picrylhydazil [DPPH] and oxygen radical absorbance capacity [ORAC]) were determined. Results. Great variability of phenolic compound content and antioxidant capacity was observed between species (inter-species) and between varieties (intra-species). The spectra with and without pre-treatments were tested to correlate with the phenolic compound content and antioxidant capacities. The pre-treatments tested showed a slight improvement in statistical parameters (R²CAL > 0.75; R²CV > 0.21; RPD > 1.1). Conclusions. The results suggest that NIR spectroscopy with chemometric approaches could be used to rapidly estimate the phenolic compound content and antioxidant capacity of the leaves of fruit species. The species evaluated in this study were shown to be a rich source of phenolic compounds and antioxidants.

Highlights

Phenolic compounds (PCs) are the most abundant secondary metabolites of plants
The results suggest that NIR spectroscopy with chemometric approaches could be used to rapidly estimate the phenolic compound content and antioxidant capacity of the leaves of fruit species
This study had two objectives: – to identify new sources of phenolic compounds and antioxidant capacity in leaves of these fruit species not yet studied; – to estimate phenolic compound content and antioxidant capacity based on electron transfer (ET) (DPPH) and hydrogen atom transfer (HAT) (ORAC) using near-infrared spectroscopy (NIRS) methods

Summary

Introduction

Phenolic compounds (PCs) are the most abundant secondary metabolites of plants. They comprise a wide variety of molecules that have a phenolic structure. They are classified according to the number of phenol rings that they contain and to the structural elements that bind these rings, forming six categories: – hydroxybenzoic acids; – hydroxycinnamic acids and coumarins; – flavonoids (anthocyanins, flavanols, flavanones, flavanonols, flavones, flavonols and isoflavones); – stilbenes; – curcuminoids; – secoridoids (Robards et al, 1999; Ignat et al, 2011). PCs are associated with increased antioxidant capacity in plant species (Robards et al, 1999; Ignat et al, 2011). PCs as antioxidants can deactivate radicals by three major mechanisms: electron transfer (ET) (for instance, 2,2-diphenyl-1-picrylhydrazyl radical [DPPH] assay and the Folin-Ciocalteu assay), hydrogen atom transfer (HAT) (for example, oxygen radical absorbance capacity [ORAC] assay), and the scavenging of reactive species (MacDonald-Wicks et al, 2006)

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Conclusion