santalol and alpha-santalene

The commercial value of Santalum album L. lies in its aromatic heartwood and essential oil. Sesquiterpenes are the main components of sandal essential oil, and these are synthesized through the plant's mevalonate (MVA) and methylerythritol phosphate (MEP) pathways. In this study, the first key rate-limiting enzyme, 1-deoxy-d-xylulose-5-phosphate synthase (SaDXS), was investigated to provide a theoretical molecular basis for the sandalwood MEP sesquiterpene biosynthetic pathway. The biofunctions of SaDXS were also analyzed. SaDXS promoters were successfully cloned from a seven-year-old S. album tree. SaDXS1A/1B promoter activity was verified by a β-glucuronidase (GUS) assay and by analyzing cis-acting elements of the promoters, which carried light- and methyl jasmonate (MeJA)-responsive signals. In an experiment involving yellow S. album seedlings, exposure to light upregulated SaDXS1A/1B expression and increased chlorophyll and carotenoid contents when overexpressed in Arabidopsis thaliana. Analysis of the expression of SaDXS1A/1B and SaSSy, key genes of santalol biosynthesis, revealed SaDXS1A expression in all tissues whereas SaDXS1B was expressed in tissues that contained photosynthetic pigments, such as stems, leaves and flowers. Sandal seedlings exogenously treated with two hormones, MeJA and ethylene, revealed similar expression patterns for SaDXS1A/1B and SaSSy. Sandal seedlings were treated with an inhibitor of DXS, clomazone, but showed no significant changes in the contents of α-santalene, β-santalene and α-santalol between treatment and control groups. These results suggest that SaDXS1A/1B play a role in the synthesis of sandalwood sesquiterpenes, providing carbon for downstream secondary metabolites. SaDXS1A/1B also play a role in the biosynthesis of chlorophyll, carotenoids, and primary metabolites.

Topics: Chlorophyll; Cloning, Molecular; Oils, Volatile; Santalum; Sesquiterpenes

The major sesquiterpene constituents of East-Indian sandalwood oil (Z)-α- and (Z)-β-santalols have shown to be responsible for most of the biological activities and organoleptic properties of sandalwood oil. The work reported here describes the strategic use of medium pressure liquid chromatography (MPLC) for the separation of both α- and β-santalenes and (Z)-α- and (Z)-β-santalols. Silver nitrate impregnated silica gel was used as the stationary phase in MPLC for quantitative separation of α- and β-santalenes and (Z)-α- and (Z)-β-santalols with mobile phases hexane and dichloromethane, respectively. The purities of α-santalene and (Z)-α-santalol obtained were >96%; however, β-santalene and (Z)-β-santalol were obtained with their respective inseparable epi-isomers. Limits of quantification (LoQ) relative to the FID detector were measured for important sesquiterpene alcohols of heartwood oil of S. album using serial dilutions of the standard stock solutions and demonstrated that the quality of the commercial sandalwood oil can be assessed for the content of individual sesquiterpene alcohols regulated by Australian Standard (AS2112-2003), International Organization for Standardization ISO 3518:2002 (E) and European Union (E. U.).

Topics: Chromatography, Liquid; Gas Chromatography-Mass Spectrometry; Plant Oils; Polycyclic Sesquiterpenes; Pressure; Santalum; Sesquiterpenes; Silica Gel; Silver Nitrate; Stereoisomerism

The action of Aspergillus niger on mono- and sesqui-terpenic hydrocarbons, such as carane, 3-carene, alpha-santalene, and humulene was studied in shake cultures. Carane, Delta3-carene, and humulene proved to be rather resistant to oxygenation by the experimental strain of A. niger. Carene yielded a hydroxyketone, C(10)H(14)O(2), in poor yields after prolonged fermentation. The sesqui-terpene hydrocarbon, alpha-santalene, was degraded mainly to an acid, tere-santalic acid. Two hydroxylated products were also obtained from alpha-santalene, viz., tere-santalol and an alcohol, C(15)H(24)O.

Topics: Alcohols; Aspergillus; Aspergillus niger; Bicyclic Monoterpenes; Bridged Bicyclo Compounds; Fermentation; Monocyclic Sesquiterpenes; Monoterpenes; Polycyclic Sesquiterpenes; Sesquiterpenes; Terpenes