Effect of levan's branching structure on antitumor activity.

Levan produced from Microbacterium laevaniformans KCTC 9732 (M-levan) was isolated and treated with an inulinase to modify its branching structure. The chemical structures of levans were characterized, and the modified levans were applied on animal tumor cells to evaluate their antitumor activity. The GC-MS analysis indicated that beta-(2,1)-linked branches of M-levan were specifically hydrolyzed. As the ratio of applied inulinase to levan increased, the branching degree decreased proportionally. Sequential degrees of branching were obtained from 12.3 to 4.2%. Strong levan-induced inhibition of cell growth was detected on SNU-1 and HepG2 tumor cell lines. As the branching degree of M-levan reduced, antitumor activity on SNU-1 linearly decreased (r2=0.96). In HepG2, the antitumor activity rapidly dropped when the branching reached up to 9.3%, then slightly increased as the branching degree of M-levan further decreased. These results suggested that the branch structure would play a crucial role in levan's antitumor activity.