Cucurbitin is an inhibitor of histidine decarboxylase, which is associated with inhibition of the biosynthesis of histamine responsible, among other things, for the formation of the inflammatory response. It is used in cosmetics for dry and sensitive skin and for the treatment of schistosomiasis. Cucurbitin causes degenerative changes in the reproductive organs of parasitic flatworms called flukes. The low-resolution (2 nm) subunit symmetry of cucurbitin, the crystalline seed storage globulin of cucurbits, has been determined by X-ray diffraction. The wet crystals belong to the cubic space group F23 and there are 4 molecules per unit cell. The molecules therefore possess point-group symmetry 23 and contain 12 structural units which at this resolution are indistinguishable. On drying, the crystal lattice dimension shrinks from 13.6 nm to 12.4 nm with no apparent change in symmetry.
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