Determination of Sugars and Sugar Alcohols in Plant Tissues by GC/MS

Sugars and sugar alcohols are the most important primary metabolites in plant tissues, which provide energy, free radical scavenging and regulation of plant cell osmotic pressure and other physiological functions. Their equilibrium is directly associated with the physiological condition of plant tissues. For example, sorbitol and mannitol are two important derivatives of monosaccharides, which are mainly involved in the regulation of osmotic stress and important for plant growth and stress signaling. These sugar and sugar alcohols are usually detected by titration, spectrophotometric method, enzymatic analysis and chromatographic analysis. However, these chemicals in plant tissue are kept at low concentration. To enhance the sensitivity for plant endogenous sugars and sugar alcohols detection, gas chromatography-mass spectrometry (GC/MS) combined with selected ion monitoring (SIM) was established. 7 kinds of sugar and sugar alcohols, including of fructose (Flu), glucose (Glu), galactose (Gal), inositol (Ino), mannitol (Man), sucrose (Suc) and sorbitol (Sor) were detected in plant tissues at a low concentration. The result showed that fructose concentration was 5.5 mg/L, the others were below 0.11 mg/L, and the relative standard deviation (RSD) was between 2.3% and 4.9%. As an application, these chemicals in Lycium chinensis tissue were detected. The contents of sucrose and glucose in root were more than 2 times these of the leaves, while the galactose and inositol had no difference in the two tissues.