Discovery of Species-Specific Peptide Markers for Superseed Authentication Using Targeted LC-MS/MS Proteomics

TL;DR

This study identifies unique protein markers to authenticate superseeds like flax and quinoa using targeted mass spectrometry.

Contribution

A standardized workflow for extracting and identifying species-specific peptides in superseeds is developed and tested.

Findings

Species-specific peptides were identified for six superseeds using targeted LC-MS/MS.

SDS buffer extraction was found to be the most effective method for protein extraction.

No reliable markers were found for chia, canihua, basil, black cumin, and psyllium seeds.

Abstract

The increasing popularity of “superseeds” such as flax, sesame, amaranth and quinoa as functional foods raises the need for robust analytical methods for authentication purposes. In this work, a standardized workflow for the extraction, characterization and identification of unique peptides that may be used as markers to distinguish superseed species was investigated. Ammonium bicarbonate/urea (Ambi/urea) extraction, sodium dodecyl sulfate (SDS) buffer and trichloroacetic acid (TCA) precipitation were initially implemented and, based on the level and composition of the extracted proteins, the SDS buffer protocol was selected. Electrophoresis analysis revealed consistent protein profiles between biological replicates from each of the eleven seed species, confirming the reproducibility of the SDS buffer protocol. Targeted mass spectrometry successfully identified species-specific peptide markers for six of eleven superseeds investigated, including peptides from conlinins in flaxseed (WVQQAK), 11S globulins in sesame (LVYIER), oleosin in quinoa (DVGQTIESK), agglutin-like lectins in amaranth (CAGVSVIR), as well as cupin-like proteins in poppy seeds (INIVNSQK) and edestins in hemp seeds (FLQLSAER). Moreover, proteome cross-analysis allowed us to disqualify the isomeric peptide LTALEPTNR from 11S globulins present in amaranth and quinoa. However, no reliable markers were identified for chia, canihua, basil, black cumin, and psyllium seeds under current conditions. While this targeted proteomics approach shows promise for superseed authentication, comprehensive method validation and alternative strategies for marker-deficient species are required before routine implementation.

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