Optimization of Solvent-Free Microwave-Assisted Hydrodiffusion and Gravity Extraction of Morus nigra L. Fruits Maximizing Polyphenols, Sugar Content, and Biological Activities Using Central Composite Design.

Ahmed M Mustafa,Gianni Sagratini,Sonia Nunez,Marco Cespi,Sauro Vittori,Giovanni Caprioli,Víctor López,Filippo Maggi,Doaa Abouelenein,Simone Angeloni,Eugenia Mazzara

doi:10.3390/ph15010099

Abstract

Black mulberry, Morus nigra L. (family: Moraceae), is a healthy food and medicinal plant. Microwave hydrodiffusion and gravity (MHG) is one of the most innovative applications of solvent-free microwave extraction. The aim of this study was to optimize for the first time the MHG solvent-free extraction of polyphenols and sugars from M. nigra fruits. Optimization was carried out using a central composite design (CCD) with selected responses such as extraction yield, total polyphenol (TPC), flavonoid (TFC), anthocyanin (TAC), and sugar (TSC) contents, in addition to DPPH radical scavenging, and α-glucosidase (AGHi), lipase (Li), and xanthine oxidase (XOi) inhibition as tools to evaluate the best parameters for efficient and rapid extraction of black mulberry. The optimized extract was characterized in terms of the aforementioned parameters to validate the models, and was further analyzed for 36 individual polyphenols using HPLC-MS/MS. The optimized MHG extract was finally compared with traditional extracts, and demonstrated much better performance in terms of TPC, TAC, and Li, while the traditional extracts showed better XOi and AGHi. In conclusion, MHG is a valuable green technique for the production of non-degraded black mulberry polyphenol-rich extract and we suggest its larger use in the pharmaceutical and food industries.

Highlights

The black mulberry (Morus nigra L.) is a Moraceae family plant that is used as a food and medicine
A study of Microwave hydrodiffusion and gravity (MHG) solventfree extraction of polyphenols and sugars from fresh fruits of black mulberry using a central composite design, with selected responses such as extraction yield, total polyphenol, flavonoid, anthocyanin, and sugar contents, in addition to α-glucosidase inhibition (AGHi), lipase inhibition (Li), xanthine oxidase inhibition (XOi), and DPPH radical scavenging activities as tools to evaluate the best parameters for rapid and efficient extraction of black mulberry
The only exception is represented by the total anthocyanin content (TAC) value, which is closer to the average value of the central composite design (CCD) runs; the TAC values suddenly declined when the microwave power (MP) reached around 1.8–1.9 W/g

Summary

Introduction

The black mulberry (Morus nigra L.) is a Moraceae family plant that is used as a food and medicine. It belongs to the genus Morus and is one of its most important species. This species is well-known for its nutritional value and unusual flavor, as well as being a good source of numerous bioactive phytonutrients [1]. The fruit of the black mulberry tree contains a high concentration of beneficial bioactive metabolites, such as phenolic compounds, which may have beneficial health effects [2]. Flavonols, and anthocyanins are the three major categories of phenolic compounds contained in black mulberry.

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Conclusion