Title: Rhein
CAS Registry Number: 478-43-3
CAS Name: 9,10-Dihydro-4,5-dihydroxy-9,10-dioxo-2-anthracenecarboxylic acid
Additional Names: 1,8-dihydroxyanthraquinone-3-carboxylic acid; 4,5-dihydroxyanthraquinone-2-carboxylic acid; chrysazin-3-carboxylic acid; monorhein; rheic acid; cassic acid; parietic acid; rhubarb yellow
Molecular Formula: C15H8O6
Molecular Weight: 284.22
Percent Composition: C 63.39%, H 2.84%, O 33.78%
Literature References: Found in the free state and as glucoside in Rheum spp, Polygonaceae (rhubarb) and in Senna leaves; also in several spp of Cassia (Leguminosae). Diacetate used as antirheumatic. Isoln from Chinese rhubarb: J. Schlossberger, O. Doepping, Ann. 50, 196 (1844); O. Hesse, ibid. 309, 32 (1899); F. Tutin, H. W. B. Clewer, J. Chem. Soc. 99, 946 (1911); from aloe-emodin, q.v.: O. A. Oesterle, Arch. Pharm. 241, 604 (1903); from Cassia alata L.: H. Hauptmann, L. L. Nazario, J. Am. Chem. Soc. 72, 1492 (1950); from C. fistula: V. K. Murty et al., Tetrahedron 23, 515 (1967). Prepn from chrysophanic diacetate: Fischer et al., J. Prakt. Chem. [2] 83, 208; 84, 369 (1911). Structure: H. Nawa et al., J. Org. Chem. 26, 979 (1961). Use in arthritis: C. A. Friedmann, DE 2711493; idem, US 4244968 (1977, 1981 both to Proter). Spectrophotometric study: A. A. Habib, N. A. El-Sebakhy, J. Nat. Prod. 43, 452 (1980). Determn by gas chromatography, mass spectroscopy: G. W. Van Eijk, H. J. Roeijmans, J. Chromatogr. 295, 497 (1984); HPLC: A. J. J. Van den Berg, R. P. Labadie, ibid. 329, 311 (1985). Pharmacological effects on colonic mucosa: R. Wanitschke, Pharmacology 20, Suppl. 1, 21 (1980); K. Ewe, ibid. 27. Metabolism study: J. Lemli, L. Lemmons, ibid. 50. In electron transport: P. Egerer et al., Z. Physiol. Chem. 363, 627 (1982). Inhibition of proteases: L. Raimondi et al., Pharmacol. Res. Commun. 14, 103 (1982). Effect on prostaglandin biosynthesis: S. Franchi-Micheli et al., J. Pharm. Pharmacol. 35, 262 (1983).
Properties: Yellow needles by sublimation, mp 321-322°, dec 330°. Absorption max (methanol): 229, 258, 435 nm (e 36800, 20100, 11100). Practically insol in water. Sol in alkalies, pyridine; slightly sol in alc, benzene, chloroform, ether, petr ether. Forms a red potassium salt and a pink sodium salt. Red precips are also obtained with Ca(OH)2 and Ba(OH)2.
Melting point: mp 321-322°
Absorption maximum: Absorption max (methanol): 229, 258, 435 nm (e 36800, 20100, 11100)
Derivative Type: Diacetate see Diacerein

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