The cyclo-hexene ring that constitutes a part of the tetra-hydroxanthene fused-ring system of the title compound, C(23)H(26)O(4), adopts a flattened half-chair conformation that approximates an envelope conformation (in which the methyl-ene C atom bearing the two methyl substituents represents the flap) as five of the six atoms lie approximately on a plane (r.m.s. deviation = 0.020 Å). The mean plane of the cyclo-hexene ring with the hy-droxy substituent is approximately perpendicular to the mean plane of the tetra-hydroxanthene system. In the crystal, adjacent mol-ecules are linked by O-H⋯O(carbon-yl) hydrogen bonds into a chain running along the b axis.