Isolation, identification and chemical modification of sesquiterpenes from Curcuma xanthorrhiza

Abstract

Curcuma xanthorrhiza locally known as temulawak is one of the medicinal plants of the ginger family. The rhizomes have been used for dyspepsia and spice. Hydrodistillation followed by GC and GCMSanalysis of the essential oil revealed the presence of many sesquiterpenes; among them are ar-curcumene, germacrone and xanthorrhizol was the major constituent. Fractionation by vacuum liquid chromatography followed by column chromatography afforded the major sesquiterpenes. Xanthorrhizol has been transformed into its simple analogues via simple reactions including methylation, epoxidation and acetylation. Xanthorrhizol has stereogenic centre at benzylic position.Thus It has been transformed to several other bioactive naturally occurring bisabolane-type sesquiterpenoids, in a stereoselective manner. 10R-and 10S-10,11-dihydro-10,11-dihydroxyxanthorrhizols, (–) -curcuquinone, (–)-curcuhydroquinone, helibisabonol A and allylic alcohol have been prepared from xanthorrhizol in optically active forms. All the routes involved a Sharpless AD to introduce the stereogenic centre at C-10. In this conference, the isolation-identification and synthesis of these bioactive sesquiterpenoids will be presented.