Seeds represent the major source of food protein, impacting on both human nutrition and animal feeding. Therefore, seed quality needs to be appropriately addressed in the context of viability and food safety. Indeed, long-term and inappropriate storage of seeds might result in enhancement of protein glycation, which might affect their quality and longevity. Glycation of seed proteins can be probed by exhaustive acid hydrolysis and quantification of the glycation adduct Nɛ-(carboxymethyl)lysine (CML) by liquid chromatography-mass spectrometry (LC-MS). This approach, however, does not allow analysis of thermally and chemically labile glycation adducts, like glyoxal-, methylglyoxal- and 3-deoxyglucosone-derived hydroimidazolones. Although enzymatic hydrolysis might be a good solution in this context, it requires aqueous conditions, which cannot ensure reconstitution of seed protein isolates. Because of this, the complete profiles of seed advanced glycation end products (AGEs) are not characterized so far. Therefore, here we propose the approach, giving access to quantitative solubilization of seed proteins in presence of sodium dodecyl sulfate (SDS) and their quantitative enzymatic hydrolysis prior to removal of SDS by reversed phase solid phase extraction (RP-SPE). Using methylglyoxal-derived hydroimidazolone 1 (MG-H1) as a case example, we demonstrate the applicability of this method for reliable and sensitive LC-MS-based quantification of chemically labile AGEs and its compatibility with bioassays.

This study arises from both the today\'s trend towards exploiting plant resources exhaustively, and the wide quantitative discrepancy between the amounts of commercially-valuable markers in aromatic plants and those recovered from the related essential oil. The study addresses the determination of both the qualitative composition and the exhaustive distribution of free and glucosidically-bound L-menthol in peppermint aerial parts (Mentha x piperita L., Lamiaceae) and of eugenol in dried cloves (Syzygium aromaticum (L.) Merr. & L.M.Perry, Myrtaceae), two plants known to provide widely ranging essential oil yields. The two markers were investigated in essential oils and residual hydrodistillation waters, before and after enzymatic hydrolysis. Their amounts were related to those in the headspace taken as reference. The results showed that the difference between marker compound in headspace and in essential oil amounted to 22.8% for L-menthol in peppermint, and 16.5% for eugenol in cloves. The aglycones solubilised in the residual hydrodistillation waters were 7.2% of the headspace reference amount for L-menthol, and 13.3% for eugenol, respectively representing 9.3% and 15.9% of their amounts in the essential oil. The amount of L-menthol from its glucoside in residual hydrodistillation waters was 20.6% of that in the related essential oil, while eugenol from its glucoside accounted for 7.7% of the amount in clove essential oil. The yield of L-menthol, after submitting the plant material to enzymatic hydrolysis before hydrodistillation, increased by 23.1%, and for eugenol the increase was 8.1%, compared to the amount in the respective conventional essential oils. This study also aimed to evaluate the reliability of recently-introduced techniques that are little applied, if at all, in this field. The simultaneous use of high-concentration-capacity sample preparation techniques (SBSE, and HS-SPME and in-solution SPME) to run quali-quantitative analysis without sample manipulation, and direct LC-MS glucoside analysis, provided cross-validation of the results.