Metabolomic analysis to study the effect of foliar copper supplementation on sulfur-containing compounds of garlic bulb by LC-MS.

INTRODUCTION

Garlic (Allium sativum L.) is renowned for its health-promoting properties, largely due to its sulfur-rich compounds. While copper is essential for plant growth and metabolism, excessive levels can disrupt cellular processes and lead to oxidative stress.

OBJECTIVES

This study aims to investigate the impact of copper supplementation on the metabolic profile of garlic, with a particular focus on changes in sulfur metabolism.

METHODS

Ito garlic cloves were harvested in 2020 on Red-Yellow Latosol soil. Copper chelate fertilizer was applied foliarly at 300 mL/ha, 30, 20, and 10 days before harvest. After harvesting, cloves were refrigerated and analyzed. Using LC-MS metabolomics, the metabolic profile of garlic was analyzed after copper supplementation to assess changes, specifically in sulfur-containing compounds.

RESULTS

Copper supplementation led to a significant reduction in key sulfur-containing metabolites critical for the health-promoting properties of garlic, including allicin (FC = 0.0947), alliin (FC = 0.0147), and γ-glutamyl-S-allylcysteine (FC = 0.0076). Enrichment analysis identified alterations in pathways related to glutamine, glutamate, alanine, and aspartate metabolism. Additionally, precursors of glutathione (GSH) were depleted, likely as a result of GSH sparing efforts to counteract copper-induced oxidative stress. This redirection may increase susceptibility to ferroptosis, a form of cell death linked to oxidative damage.

CONCLUSION

The metabolomic analysis of copper-supplemented Ito garlic cloves showed a significant reduction in sulfur compounds allicin, alliin, and γ-glutamyl-S-allylcysteine, important for organoleptic and medicinal properties. This decrease indicates a metabolic shift towards antioxidant defenses, with glutathione being redirected to defense pathways rather than secondary metabolites. Future studies should explore oxidative stress and ferroptosis markers, and lipidomics for a deeper understanding of garlic response to copper exposure.