Abstract
We analyzed the human monocyte-stimulating ability of laminarin from Eisenia bicyclis, lichenan from Cetraria islandica, and their oligomers depolymerized with endo-1,3-β-glucanase from Arthrobacter sp. The respective β-glucan oligomers with different degrees of polymerization (DP) were fractionated from hydrolytic products of laminarin and lichenan using gel-filtration chromatography. The monocyte-conditioned medium pre-cultured in the presence of a fraction of β-glucan oligomer (DP≥8) from laminarin exhibited inhibitory activity against the proliferation of human myeloid leukemia U937 cells, while those pre-cultured with other β-glucan oligomers and the original laminarin and lichenan showed little or no activity. NMR analysis indicated that the β-glucan oligomer (DP≥8) has an average DP value of 13, and its ratio of β-1,3- to β-1,6-linkages in glucopyranose units was estimated to be 1.3:1. These results indicate that the β-1,3-glucan oligomer with a higher content of β-1,6-linkage stimulates monocytes to inhibit the proliferation of U937 cells.
