Exploring Tuscany onion (Allium cepa L.) heritage: unveiling ancient varieties through molecular network analysis and bioinformatic tools

Preserving plant biodiversity and making sustainable use of genetic resources in agriculture is a topical issue with ecological, economic, and social repercussions (Ebert et al., 2020). Allium cepa L. (Amaryllidaceae) is worldwide studied as an important source of dietary phytochemicals (Tedesco et al., 2015). In Italy, some onion varieties, only cultivated by local farmers, are neglected and worth to be valorized. The aim of this work was to investigate for the first time the chemical composition of 10 indigenous Tuscany onion varieties, by comparing with the marketed “Tropea”, “Fiorentina”, and “Di Certaldo” onions. The chemical fingerprint was obtained by processing LC-qTOF-MS/MS data with MZmine3 (Schmid et al., 2023), generating molecular networks with MetGem (Olivon et al., 2018) and using compound annotation tools. Flavonoids such as kaempferol, (dihydro)quercetin and isorhamnetin derivatives, were detected in all the samples, thought in different relative ratio. “Di Certaldo” variety distinguished from the others for a molecular cluster of sulphur-containing compounds. “Acquaviva” and “Treschietto” displayed the presence of fatty acids and amino acids derivatives not detected in other samples. Combining the acquisition of large, high-resolution experimental datasets with powerful informatics tools, it was possible to identify the most known bioactive compounds distribution but also highlight the presence of molecular clusters specific to a few onion varieties, potentially correlated with the biological findings. As future work, the extracts will be investigated for their antiangiogenic activity by two in vivo models, chick chorioallantoic membrane/zebrafish embryos. References Ebert, A.W., Engels, J.M.M., 2020. Plant biodiversity and genetic resources matter! Plants 9, 1706. Olivon, F., Elie, N., Grelier, G., Roussi, F., Litaudon, M., Touboul, D., 2018. MetGem software for the generation of molecular networks based on the t-SNE algorithm. Anal. Chem. 90, 13900-13908. Schmid, R., Heuckeroth, S., Korf, A., Smirnov, A., Myers, O. et al., 2023. Integrative analysis of multimodal mass spectrometry data in MZmine 3. Nat. Biotechnol. 41, 447-449. Tedesco, I., Carbone, V., Spagnuolo, C., Minasi, P., Russo, G.L., 2015. Identification and quantification of flavonoids from two southern Italian cultivars of Allium cepa L., Tropea (Red Onion) and Montoro (Copper Onion), and their capacity to protect human erythrocytes from oxidative stress. J. Agric. Food Chem. 63, 5229-5238.