Characterization of α-humulene synthases responsible for the production of sesquiterpenes induced by methyl jasmonate in Aquilaria cell culture.

The resinous portions of Aquilaria and Gyrinops plants are known as 'agarwood' and have a distinctive fragrance. To examine the biosynthesis of these fragrant compounds, we previously established cell cultures of Aquilaria crassna in which the production of three sesquiterpenes (α-guaiene, α-humulene, and δ-guaiene) could be induced by methyl jasmonate (MJ), and showed that cloned δ-guaiene synthase from MJ-treated cells is involved in the synthesis of these three compounds, although only very small amounts of α-humulene are produced. In the present study, cDNAs encoding α-humulene synthases were also isolated. Three putative sesquiterpene synthase clones (AcHS1-3) isolated from the MJ-treated cells had very similar amino acid sequences and shared 52 % identity with δ-guaiene synthases. The recombinant enzymes catalyzed the formation of α-humulene as a major product. Expression of transcripts of the α-humulene synthase and δ-guaiene synthase genes in cultured cells increased after treatment with MJ. These results revealed that these α-humulene and δ-guaiene synthases are involved in the synthesis of three sesquiterpenes induced by MJ treatment.

Evaluation of the botanical origin of black cohosh products by genetic and chemical analyses.

Despite the increasing sales of black cohosh (the dried rhizome and root of Cimicifuga racemosa L.) in the world herbal market, these products have continuous adulteration issues. The botanical authenticity of the black cohosh products is the first important step for ensuring their quality, safety and efficacy. In this study, we genetically identified the botanical sources of 10 black cohosh products and 5 Cimicifuga Rhizome crude drugs of Japanese Pharmacopoeia grade, and analyzed the metabolic profiling of 25 black cohosh products using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Consequently, we found that C. dahurica and possibly C. foetida are misused as sources of the black cohosh products and in some cases, the extracts of black cohosh were adulterated with the plant materials of C. dahurica. We demonstrated that these three species can be distinguished by three marker compounds in a specific mass range. These results must be helpful in establishing regulations for the safe use of the black cohosh products.

Isoheleproline: a new amino acid-sesquiterpene adduct from Inula helenium.

A new amino acid-sesquiterpene adduct, isoheleproline (1), was isolated from the roots of Inula helenium (elecampane), together with four known sesquiterpene lactones (2-5). The planar configuration of 1 was elucidated on the basis of spectroscopic data analysis, and the relative configuration of 1 was determined by performing a detailed analysis of NOESY correlations and comparing its physicochemical data with the D- and L-proline adducts of 2 obtained by Michael addition. This is the first report of a new amino acid-sesquiterpene adduct from Inula plants.

Species identification of Asini Corii Collas (donkey glue) by PCR amplification of cytochrome b gene.

Asini Corii Collas (ACC; donkey glue) is a crude drug used to promote hematopoiesis and arrest bleeding. Because adulteration of the drug with substances from other animals such as horses, cattle, and pigs has been found, we examined PCR methods based on the sequence of the cytochrome b gene for source species identification. Two strategies for extracting DNA from ACC were compared, and the ion-exchange resin procedure was revealed to be more suitable than the silica-based one. Using DNA extracted from ACC by the ion-exchange resin procedure, PCR methods for species-specific detection of donkey, horse, cattle, and pig substances were established. When these species-specific PCR methods were applied to ACC, amplicons were obtained only by the donkey-specific PCR. Cattle-specific PCR detected as little as 0.1% admixture of cattle glue in the ACC. These results suggest that the species-specific PCR methods established in this study would be useful for simple and easy detection of adulteration of ACC.

Chemical analysis reveals the botanical origin of shatavari products and confirms the absence of alkaloid asparagamine A in Asparagus racemosus.

Shatavari-a famous Ayurveda materia medica used mainly as a tonic for women-is distributed in health food products all over the world. The Ayurvedic Pharmacopoeia of India identifies the botanical origin of shatavari as the tuberous root of Asparagus racemosus. We recently investigated by DNA analysis the botanical origin of shatavari products on the Japanese market. The results suggested that their botanical origin was Asparagus; however, species identification was difficult. In this study, we analyzed steroidal saponins, including those specific to this plant, in these products and confirmed their origin as A. racemosus. Next, alkaloid analyses of an authentic A. racemosus plant and these products were performed, because several papers have reported the isolation of a pyrrolo[1,2-a]azepine alkaloid, asparagamine A, from this plant. Our results suggest that neither plant material nor products contained asparagamine A. It has been pointed out that Stemona plants are sometimes mistaken for shatavari, because their tuberous roots have a similar shape to that of A. racemosus, and pyrrolo[1,2-a]azepine alkaloids are thought to be Stemona-specific. These data strongly suggest that A. racemosus does not contain asparagamine A, and that previous isolation of asparagamine A from materials claimed as originating from A. racemosus was likely caused by misidentification of Stemona plants as A. racemosus.

Genomic organization of δ-guaiene synthase genes in Aquilaria crassna and its possible use for the identification of Aquilaria species.

The resinous portions of Aquilaria plants, called agarwood, have been used as medicines and incenses. Agarwood contains a great variety of sesquiterpenes, and a study using cultured cells of Aquilaria crassna showed that the production of sesquiterpenes (α-guaiene, α-humulene, and δ-guaiene) was induced by treatment with methyl jasmonate, which led to the cloning of δ-guaiene synthases. In the present study, analyses of genomic organization and Southern blotting of δ-guaiene synthase in A. crassna were performed in order to examine the genomic background of δ-guaiene synthases in Aquilaria plants. Genomic cloning and sequencing revealed five types of sequence in putative δ-guaiene synthases sharing more than 96% identity in exon regions, and that these enzymes belonged to the class III TPS subfamily with seven exons and six introns. Furthermore, Southern blotting revealed that at least five copies of δ-guaiene synthase existed in A. crassna. The hybridization of digested DNA of A. crassna and A. sinensis with probes made with a δ-guaiene synthase cDNA fragment resulted in different banding patterns for these two species. It may be possible to identify Aquilaria species by restriction fragment length polymorphism analyses with δ-guaiene synthase cDNA probes.

Characterization of delta-guaiene synthases from cultured cells of Aquilaria, responsible for the formation of the sesquiterpenes in agarwood.

The resinous portions of Aquilaria plants, called agarwood, have been used as medicines and incenses. Agarwood contains a great variety of sesquiterpenes, and a study using cultured cells of Aquilaria showed the production of sesquiterpenes (α-guaiene, α-humulene, and δ-guaiene) to be induced by treatment with methyl jasmonate (MJ). In this study, the accumulation and production of sesquiterpenes were quantified. The amounts accumulated and produced reached a maximum at 12 h, and the most abundant product was α-humulene at 6 h and δ-guaiene after 12 h. However, a headspace analysis of the cells revealed that α-humulene is likely to be volatilized; so overall, the most abundant sesquiterpene in the cells was δ-guaiene. A cDNA library from RNA isolated from MJ-treated cells was screened using PCR methodologies to isolate five clones with very similar amino acid sequences. These clones were expressed in Escherichia coli, and enzymatic reactions using farnesyl pyrophosphate revealed that three of the clones yielded the same compounds as extracted from MJ-treated cells, the major product being δ-guaiene. These genes and their encoded enzymes are the first sesquiterpene synthases yielding guaiane-type sesquiterpenes as their major products to be reported. Expression of a fourth terpene synthase gene in bacteria resulted in the accumulation of the protein in insoluble forms. Site-directed mutagenesis of the inactive clone and three-dimensional homology modeling suggested that the structure of the N-terminal domain was important in facilitating proper folding of the protein to form a catalytically active structure.