Insights into tobacco leaf quality deterioration under long-term storage by investigating dynamic phytochemical and metabolite profile variations.

BACKGROUND

Storage conditions affect the metabolome composition and quality of tobacco leaf and, therefore, its economic value. The present study was designed to reveal tobacco leaves' dynamic phytochemical and metabolite profile changes under three different storage conditions: natural (NT), mechanical (MC), and air-conditioning (AC). The 210,003 grade (Hubei Central Tobacco) was selected as the experimental material, and the changes in iodine value absorbance (IV), pH, polyphenols, plastid pigments, conventional chemical compositions, and metabolite profile were analyzed at different times (T0, starting day; T1, three months; T2, five months; and T3, nine months) during storage.

RESULTS

The IV significantly increased with the storage duration, while the pH, polyphenols, and stromal pigments had the opposite trends. Lutein, β-carotene, and chlorogenic acid were significantly less degraded under MC and AC than NT. Neoxanthin and chlorophyll b were completely degraded at T3. The nicotine, total sugar, reducing sugar, and chlorine content significantly varied along with the storage duration, reaching their maximum values at T2 under MC and AC. The sugar/base ratio at T3 under MC and AC was 8.53 and 8.44, respectively, higher than in NT (5.85). LC-MS-based untargeted metabolomics analysis identified 124‒224, 138‒180, and 110‒153 significant differential accumulated metabolites (DAMs) under NT, MC, and AC, respectively. Biosynthesis of secondary metabolites was significantly induced under the three storage conditions between T0 and T3. Glutathione metabolism and oxidative phosphorylation were induced under NT. Biosynthesis of terpenoids and steroids was highly induced under AC.

CONCLUSIONS

Our findings may facilitate the optimization of the storage conditions for better preservation of tobacco leaves.

CLINICAL TRIAL NUMBER

Not applicable.