Antityrosinase Activity of Combretum micranthum, Euphorbia hirta and Anacardium occidentale Plants: Ultrasound Assisted Extraction Optimization and Profiling of Associated Predominant Metabolites.

Hussein Zeitoun,Dominique Salameh,Roger Lteif,Zareen Khan,Kaushik Banerjee

doi:10.3390/molecules25112684

Hussein Zeitoun, Dominique Salameh + Show 3 more

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https://doi.org/10.3390/molecules25112684

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Abstract

Tyrosinase is an important component of the enzyme polyphenol oxidase, which upon contact with the phenolic substrates forms the pigment melanin and induces undesirable food browning. The phenolic and triterpenoid compounds that naturally occur in plants are well known as tyrosinase inhibitors. Combretum micranthum (CM) leaves, Euphorbia hirta (EH) plant, and Anacardium occidentale (AO) fruits are traditionally known to have potential anti-tyrosinase activities. The aim of this study was to optimize the ultrasound-assisted extraction of secondary metabolites from these matrices, and to evaluate in tubo the antityrosinase activity of these extracts. Efforts were also taken to profile the secondary metabolites, mainly the phenolic and triterpenoid compounds, in order to understand their probable association with tyrosinase inhibition. The optimal ultrasound-assisted extraction conditions for simultaneous extraction of phenolic, and triterpenoid compounds were determined. The aqueous fraction of these extracts showed significant antityrosinase activity, with the CM leaves exhibiting the strongest inhibitory effect (IC50 of 0.58 g·L−1). The predominant metabolic compounds from these natural extracts were putatively identified by using a high-resolution quadrupole-time of flight (QToF) LC-MS instrument. The high-resolution accurate mass-based screening resulted in identification of 88 predominant metabolites, which included dihydrodaidzein-7-O-glucuronide, micromeric acid, syringic acid, morin, quercetin-3-O-(6″-malonyl-glucoside), 4-hydroxycoumarin, dihydrocaffeic acid-3-O-glucuronide, to name some, with less than 5 ppm of mass error.

Highlights

The browning effect can degrade the appearance, nutritional value, shelf life and marketability of fruits and vegetables [1]
From the Analysis of variance (ANOVA) (Table 2), it was found that R2 for Combretum micranthum (CM), Euphorbia hirta (EH) and Anacardium occidentale (AO) for the two responses were higher than 80%
This work marks the first extensive study of the most predominant phenolic compounds and other phytochemicals in the extracts of CM leaves, EH plant and AO fruits that have shown to be effective in inhibiting the enzymatic activity of tyrosinase

Summary

Introduction

The browning effect can degrade the appearance, nutritional value, shelf life and marketability of fruits and vegetables [1]. The high importance of food safety in the industry leads researchers across the world to a quest for natural plant-based browning inhibitors as they are anticipated to be free of unkind side effects [2,3]. The anti-browning agents that are commonly used in food industry include butylated hydroxytoluene, butylated hydroxyanisole, and propyl gallate, these compounds are suspected to cause liver damage, and carcinogenesis [4,5]. It has been demonstrated that the tyrosinase inhibitors in plant extracts work synergistically, and provide browning inhibitory activities [6]. Since plant extracts contain numerous phenolic and triterpenoid compounds with potential antityrosinase activities, they are expected to provide a high inhibitory effect on browning reactions. Lim et al examined the inhibitory effects of chemical agents vis-à-vis natural products on the polyphenol oxidase activity in sweet potatoes, and reported a slightly lower inhibition in comparison to the chemical agents [3]

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