Process Optimization for Improved Phenolic Compounds Recovery from Walnut (Juglans regia L.) Septum: Phytochemical Profile and Biological Activities.

Marius Rusu,Ioan Tomuta,Cadmiel Moldovan,Ana-Maria Gheldiu,Daniela-Saveta Popa,Andrei Mocan,Laurian Vlase

doi:10.3390/molecules23112814

Marius Rusu, Ioan Tomuta + Show 5 more

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https://doi.org/10.3390/molecules23112814

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Abstract

Plant by-products can be valuable sources of polyphenol bioactive compounds. Walnut (Juglans regia L.) is a very important tree nut rich in biologically active molecules, but its septum was scarcely researched. Experimental data indicated a hypoglycemic effect of septum extracts, with almost no details about its phytochemical composition. The main objectives of this study were: (1) to obtain walnut septum (WS) extracts with high content in bioactive compounds and antioxidant activity based on an original experimental design; (2) characterization of the phytochemical profile of the WS extracts using HPLC-MS/MS; (3) evaluation of the biological potential of the richest polyphenolic WS extract. The variables of the experimental design were: extraction method (maceration and Ultra-Turrax extraction), temperature, solvent (acetone and ethanol), and percentage of water in the solvent. The first quantifiable responses were: total phenolic content, total flavonoid content, condensed tannins, and ABTS antioxidant capacity. The phytochemical profile of lyophilized extracts obtained by Ultra-Turrax extraction (UTE), the most efficient method, was further determined by HPLC-MS/MS analysis of individual polyphenolic and phytosterols compounds. It is the first study to assay the detailed composition of WS in hydrophilic and lipophilic compounds. The biological potential of the richest polyphenolic WS extract was also evaluated by FRAP and DPPH antioxidant capacity and the inhibition of tyrosinase, an enzyme involved in the browning in fruits and vegetables, skin wrinkles and aging. Conclusion: The phytochemical profile of the analyzed extracts proves that WS can be a valuable source of biologically active compounds (polyphenols) for food and/or pharmaceutical industry and warrant the continuation of current research in further evaluating its bioactive potential.

Highlights

Each year the food industry creates a substantial amount of waste and serious issues are associated with its disposal
This study aimed to characterize septum extracts of walnut (Juglans regia) and to describe the optimum experimental conditions for maximizing the extraction efficiency of the bioactive compounds found in this less-studied by-product of this species, in the light of its traditional uses as a remedy for colds and coughs
In order to determine the optimal extraction conditions of the main phenolics and phytosterols, several parameters, such as extraction method, solvent, temperature, water percentage, were combined, and they were coupled with statistical tools and chemical analysis (LC-MS/MS)

Summary

Introduction

Each year the food industry creates a substantial amount of waste and serious issues are associated with its disposal. Overweight and obesity are increasingly seen as major concerns for human health [3]. Excessive body weight, associated with several pro-inflammatory cytokines (e.g., leptin, interleukin 6, interleukin 8, tumor necrosis factor-alpha), and a chronic, low-grade inflammation [5], is seen as a major risk factor for obesity-associated diseases, such as metabolic dysfunction [6], diabetes [7], cardiovascular diseases [8], and cancers [9], including endometrial [10], breast [11], gastrointestinal [12], pancreatic [13], prostate [14], hepatic [15], renal [16], colorectal [17]

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