Expanding the Role of Sub-Exploited DOE-High Energy Extraction and Metabolomic Profiling towards Agro-Byproduct Valorization: The Case of Carotenoid-Rich Apricot Pulp.

Thalia Tsiaka,Dimitra Z Lantzouraki,Eleni Siapi,Vassilia J Sinanoglou,Panagiotis Zoumpoulakis,Charalambos Fotakis,Konstantinos Tsiantas

doi:10.3390/molecules25112702

Thalia Tsiaka, Dimitra Z Lantzouraki + Show 5 more

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https://doi.org/10.3390/molecules25112702

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Abstract

Traditional extraction remains the method-of-choice for phytochemical analyses. However, the absence of an integrated analytical platform, focusing on customized, validated extraction steps, generates tendentious and non-reproducible data regarding the phytochemical profile. Such a platform would also support the exploration and exploitation of plant byproducts, which are a valuable source of bioactive metabolites. This study deals with the incorporation of (a) the currently sub-exploited high energy extraction methods (ultrasound (UAE)- and microwave-assisted extraction (MAE)), (b) experimental design (DOE), and (c) metabolomics, in an integrated analytical platform for the extensive study of plant metabolomics and phytochemical profiling. The recovery of carotenoids from apricot by-products (pulp) is examined as a case study. MAE, using ethanol as solvent, achieved higher carotenoid yields compared to UAE, where 1:1 chloroform-methanol was employed, and classic extraction. Nuclear magnetic resonance (NMR)-based metabolomic profiling classified extracts according to the variations in co-extractives in relation to the extraction conditions. Extracts with a lower carotenoid content contained branched-chain amino acids as co-extractives. Medium carotenoid content extracts contained choline, unsaturated fatty acids, and sugar alcohols, while the highest carotenoid extracts were also rich in sugars. Overall, the proposed pipeline can provide different the phytochemical fractions of bioactive compounds according to the needs of different industrial sectors (cosmetics, nutraceuticals, etc.).

Highlights

Plant metabolomics is the answer to traditional phytochemical approaches, which are focused on the analysis of specific targeted metabolites, usually a group of bioactive compounds, and not on the complete and detailed metabolic profile of the plant substrate or plant byproducts
The step of sample preparation is of the utmost importance, since the information provided by high throughput analytical techniques is highly dependent on the selected extraction method
Traditional extraction methods are based on the previous experience and knowledge of the researchers, who apply them without further optimization or validation

Summary

Introduction

Plant metabolomics is the answer to traditional phytochemical approaches, which are focused on the analysis of specific targeted metabolites, usually a group of bioactive compounds (i.e., carotenoids, polyphenols, alkaloids, and amino acids), and not on the complete and detailed metabolic profile of the plant substrate or plant byproducts. The different composition of the plant matrix, any possible enzymatic degradation or chemical breakdown of plant metabolites, and the lack of a tailor-made validated extraction step crucially affect the final quality of the metabolomic study and Molecules 2020, 25, 2702; doi:10.3390/molecules25112702 www.mdpi.com/journal/molecules. Molecules 2020, 25, 2702 the number of identified metabolites [1]. Among these factors, the step of sample preparation is of the utmost importance, since the information provided by high throughput analytical techniques is highly dependent on the selected extraction method. Traditional extraction methods are based on the previous experience and knowledge of the researchers, who apply them without further optimization or validation. High energy extraction methods (e.g., ultrasound-assisted extraction (UAE) or microwave-assisted extraction (MAE)) are gaining ground, but are still ignored or sub-exploited in plant metabolomics studies

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