Enhanced Recovery of Phenolic and Tocopherolic Compounds from Walnut (Juglans Regia L.) Male Flowers Based on Process Optimization of Ultrasonic Assisted-Extraction: Phytochemical Profile and Biological Activities.

Anca Pop,Julien Cherfan,Mihai Babota,Ana-Maria Gheldiu,Ionel Fizeșan,Ioan Tomuta,Daniela-Saveta Popa,Laurian Vlase,Marius Emil Rusu

doi:10.3390/antiox10040607

Abstract

The extraction of bioactive compounds present in walnut (Juglans regia L.) male flowers (WMFs) was performed based on an experimental design using ultrasonic-assisted extraction. Solvent nature, extraction time, and water content were selected as experimental variables, and phenolic, flavonoidic, and condensed tannins contents and antioxidant properties were evaluated. Acetone was the solvent with the highest extraction performance, with the extracts obtained using this solvent displaying an increased concentration of bioactive compounds and increased antioxidant activities. For several extracts with high bioactive content, individual polyphenolic and tocopherolic compounds were evaluated by means of LC-MS and LC-MS/MS. The best extraction conditions for polyphenolic (2.86 mg gallic acid equivalents/g WMF) and tocopherolic compounds (29.4 µg/g WMF) were acetone with 40% water content (N20) and acetone with 20% water content (N15), respectively. Although the total tocopherol concentrations were lower than in other Juglans regia parts, most of the total tocopherol quantity was provided by the highly biologically active δ-tocopherol (84%). Significant quantities of quercetin (101.9 µg/g), hyperoside (2662.9 µg/g), quercitrin (405.7 µg/g), and isoquercitrin (1293.7 µg/g) were determined in WMF (N20). Both extracts inhibited the enzymatic activity of α-glucosidase and tyrosinase; however, an increased inhibition was observed for N20, the extract with the higher polyphenolic content. Conversely, N15 had higher anticancerous activity on the cell lines used, with a moderate selectivity towards the cancerous phenotype being observed for both extracts. At non-cytotoxic concentrations, both extracts displayed good antioxidant activities in cellular cultures, decreasing basal and H2O2-induced oxidative stress. This is the first characterization of both hydrophilic and lipophilic phytochemicals in WMF extracts. The outcomes of our study reveal that walnut male flowers have strong biological activities, thus justifying further research to demonstrate their usefulness in the food, pharmaceutical, and/or cosmetic industries.

Highlights

The English or common walnut (Juglans regia L.), belonging to Juglandaceae family, is an important source of nutrients and bioactive compounds, especially phenolics, with notable antioxidant activity and therapeutic potential
Conclusions wewe characterized the phytochemical profileprofile of walnut (Juglans(Juglans regia L.)
Study, characterized the phytochemical of walnut male flowers and systemically investigated the experimental conditions required for achievregia L.) male flowers and systemically investigated the experimental conditions required ing high extraction efficiencies of active phytochemicals from this by-product through for achieving high extraction efficiencies of active phytochemicals from this by-product accessibleaccessible and efficient extraction

Summary

Introduction

The English or common walnut (Juglans regia L.), belonging to Juglandaceae family, is an important source of nutrients and bioactive compounds, especially phenolics, with notable antioxidant activity and therapeutic potential. The walnut tree has a long history of medicinal use, being widely used in traditional medicine in many countries [1,2] Walnuts, due to their content of protein, fibers, essential fatty acids, vitamins and minerals, as well as other phytochemicals, are ingredients in different diets recommended to prevent aging and age-related diseases [3], and in the nutrition of people with cardiovascular or neurodegenerative conditions, type II diabetes or cancer [1,4,5]. The leaf and green husk extracts have demonstrated antioxidant and anti-inflammatory activities; antidiabetic effects; and astringent, antiseptic, and anthelmintic properties [2,7]. The walnut septum contains bioactive compounds with antioxidant, anti-inflammatory, antitussive and antidiabetics properties and has a high potential for hematologic regeneration and anti-aging activity, demonstrated both in vitro [8,9,10] and in vivo [10,11,12,13,14]

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