A new approach to procyanidins synthesis with potent anti-adipogenic effects.

Convenient structure modification of (+)-catechin (1) induced by nonthermal dielectric barrier discharge (DBD) plasma treatment afforded three novel methylene-linked flavan-3-ol oligomers, methylenetetracatechin (2), methylenetricatechin (3), and methylenedicatechin (4), together with two known catechin dimers, bis 8,8'-catechinylmethane (5) and bis 6,8'-catechinylmethane (6). The structures of the three new catechin oligomers 2-4 with methylene bridges were elucidated by detailed 1D- and 2D-NMR analysis, and the absolute configurations were established by the observation of circular dichroism (CD). The novel products 2 and 3 showed significantly enhanced anti-adipogenic capacities against both pancreatic lipase and differentiation of 3T3-L1 preadipocytes compared to the parent (+)-catechin.