Analyses of quality and metabolites levels of okra during postharvest senescence by 1H-high resolution NMR

Okra were stored for 19 days at 25 degrees C and nuclear magnetic resonnance spectroscopy was used to monitor the changes of metabolite levels. Seventeen metabolites were identified and their relative levels were analysed by principal component analysis. The first principal components were isoleucine, fatty acids, gamma-aminobutyrate, glutamine, asparagine, unsaturated lipids, choline, phosphocholine and cinnamic acid. Decreases of glucose and sucrose levels were responsible for the quality reduction. Accumulation of cinnamic acid was involved in the lignification of okra tissue in the late storage period. Amino acids and gamma-aminobutyrate levels increased during storage, which indicated the degradation of proteins. Increased electrolyte leakage and chlorophyll loss were also observed. The results indicated that NMR technique could be a good choice for metabolomic analysis of okra.