Abstract

Agave plants are members of the Agavaceae family and utilize crassulacean acid metabolism (CAM) for CO₂ fixation. Fructans are the main photosynthetic products produced by Agave plants, and are their principal source of storage carbohydrates. The aim of this work was to determine the chemical and molecular characterization of fructans from Agave durangensis. Fructans were extracted from 10 year old A. durangensis plants. Trimethylsilyl derivatization was employed to determine the monomer composition. The linkage types in these carbohydrates were determined by methylation followed by reduction and O-acetylation, and finally analysis by gas chromatography-mass spectrometry (GC-MS). Samples were shown to contain t-β-D-Fruf, t-α-D-Glup, i-α-D-6-Glup and 1,6-di-β-D-Fruf linkages. The analysis of the degree of polymerization (DP) was confirmed by MALDI-TOF-MS, showing a wide DP ranging from 2 to 29 units. The analyses performed revealed that fructans from A. durangensis are formed of 97.11% fructose and 2.89% glucose, and are a complex mixture of fructooligosaccharides of the neo-fructan type containing principally β(2-1) and β(2-6) linkages, with branch moieties.

Key words: Degree of polymerization (DP), GC-MS, MALDI-TOF-MS.

Abbreviation

DMSO, Dimethyl sulfoxide; TFA, trifluoroacetic acid; EtOH, ethanol; HMDS, hexamethyldisilazane; NaOH, sodium hydroxide; CH₃I, iodomethane; NaBD₄, sodium borodeuteride; NH₄OH, ammonium hydroxide; N₂, nitrogen; CO₂, carbon dioxide; H₂O, water; CAM, crassulacean acid metabolism; PAAMs, partially methylated alditol acetates; WSC, water soluble carbohydrates; DP, degree of polymerization; GC-MS, gas chromatography-mass spectrometry; MALDI-TOF-MS, matrix-assisted laser desorption time-of-flight mass spectrometry.