Structural Characterization and In Vitro Cytokines Modulation Effect of New Acetylated Galactomannans from Aloe arborescens.

Three new galactomannan components designed as AANP-1, AANP-3, and AAAP-7 were isolated from previously purified Aloe arborescence polysaccharide fractions, using ion-exchange, gel filtration, and preparative chromatographic techniques. Based on Fourier transform-infrared, one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy, the main backbone of AANP-1 elucidated as (1 → 4)-linked_α-d-deoxyGalp, (1 → 4) d-Manp, and β-d-2-glup. The sugar residue sequence of AANP-3 was (1 → 4)-linked β-d-NHAC-GAlp with β-d-AcManp side chain that attached to O-4 position. The AAAP-7 repeated units were (1 → 4) d-Manp linked with (1 → 4) d-Galp interspersed with (1 → 3)-α-Manp. The results of high performance size-exclusion chromatography indicated that the approximate molecular weights of AANP-1, AANP-3, and AAAP-7 were 4.2, 2.4, and 2.5 kDa, respectively. The cytokine modulation assay revealed that the isolated components promoted a remarkable release of interleukin (IL)-12 and tumor necrosis factor alpha in comparison with the negative control group, whereas potent significant induction of IL-2 and interferon gamma was detected more than the positive control phytohemagglutinin (P < .05). This is the first report for isolation galactomannans from Aloe arborescence. Moreover, this finding could provide new insights for exploring the biological modifier mechanism in correlation with the knowledge of structural configuration.