Metabolomics Reveal the Chemical Characteristic of Cigar Tobacco Leaves During Air-Curing Process

Abstract

Air-curing is a critical process in the production of cigar tobacco leaves. This process involves the vital degradation and transformation of macromolecular substances into micromolecular chemical compounds. In this study, three different varieties of tobacco leaves harvested from the Wuzhishan and Danzhou areas of Hainan, China were used as materials. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was employed to investigate the chemical changes before and after air-curing in the metabolites. Metabolic analysis revealed significant stepwise alterations in the tobacco leaf metabolome during the air-curing process. A total of 172 differential metabolites were identified as significant contributors in the biosynthesis pathways of flavonoids, flavone, flavonol, and other secondary metabolites, among the total analyzed 1841 metabolites obtained from the tobacco leaves. Notably, the contents of flavonoid metabolites, including kaempferol, rutin, chlorogenic acid, and quercetin, exhibited a significant decrease throughout the air-curing period. Correlation analysis indicated a strong association between the biosynthesis of flavonoids and the contents of chlorogenic acid and kaempferol, suggesting their role in regulation the formation of yellow and brown colors in tobacco leaves. These findings provide valuable insights for future investigations into the quality, commercial value, and chemical properties of cigar tobacco.