Bergenin monohydrate from the rhizomae of Astilbe chinensis.

The title compound, 4-methoxy-2-[(1S,2R,3S,4S,5R)-3,4,5,6-tetrahydro-3,4,5-trihydroxy-6-(hydroxymethyl)-2H-pyran-2-yl]-alpha-resorcylic acid delta-lactone monohydrate, C(14)H(16)O(9).H(2)O, is a C-glucoside of 4-O-methylgallic acid which has antiasthmatic, antitussive, anti-inflammatory, antifungal, anti-HIV and antihepatotoxic activity. The molecule is composed of three six-membered rings: an aromatic ring, a glucopyranose ring and an annellated delta-lactone ring. The glucopyranose ring exhibits only small deviations from an ideal chair conformation. The annellated delta-lactone ring possesses the expected half-chair conformation. There is one intra- and six intermolecular hydrogen bonds which form an extensive hydrogen-bonding network within the crystal.