Constituents of a Fern, Davallia mariesii MOORE. V. Isolation and Structures of Davallin, a New Tetrameric Proanthocyanidin, and Two New Phenolic Glycosides.

A new tetrameric proanthocyanidin named davallin (1) and two new phenolic glycosides, 5-O-β-D-(6-O-vanilloylglucopyranosyl)gentisic acid (6) and 4-O-β-D-(6-O-vanilloylglucopyranosyl)vanillic acid (7), have been isolated from the rhizomes of Davallia mariesii MOORE together with six known compounds, procyanidin B-2 (2) and B-5 (3), epicatechin-(4β→8)-epicatechin-(4β→6)-epicatechin (4), epicatechin-(4β→6)-epicatechin-(4β→8)-epicatechin-(4β→6)-epicatechin (5), protocatechuic acid (8), and 1-naphthol-β-D-glucopyranoside (9). Structures of the three new compounds (1, 6, and 7) were determined by means of spectroscopic methods including two-dimensional NMR techniques.Among the compounds obtained, 1 and 2 inhibited protein kinase C with IC50 values of 3.5 and 8.6 μM, respectively.