[Chemical Constituents from Dalbergia cochinchinensis].[Pubmed: 26930980]

To investigate the chemical constituents from the heartwood of Dalbergia cochinchinensis.

The Use of DNA Barcoding in Identification and Conservation of Rosewood (Dalbergia spp.).[Pubmed: 26375850]

The genus Dalbergia contains many valuable timber species threatened by illegal logging and deforestation, but knowledge on distributions and threats is often limited and accurate species identification difficult. The aim of this study was to apply DNA barcoding methods to support conservation efforts of Dalbergia species in Indochina. We used the recommended rbcL, matK and ITS barcoding markers on 95 samples covering 31 species of Dalbergia, and tested their discrimination ability with both traditional distance-based as well as different model-based machine learning methods. We specifically tested whether the markers could be used to solve taxonomic confusion concerning the timber species Dalbergia oliveri, and to identify the CITES-listed Dalbergia cochinchinensis. We also applied the barcoding markers to 14 samples of unknown identity. In general, we found that the barcoding markers discriminated among Dalbergia species with high accuracy. We found that ITS yielded the single highest discrimination rate (100%), but due to difficulties in obtaining high-quality sequences from degraded material, the better overall choice for Dalbergia seems to be the standard rbcL+matK barcode, as this yielded discrimination rates close to 90% and amplified well. The distance-based method TaxonDNA showed the highest identification rates overall, although a more complete specimen sampling is needed to conclude on the best analytic method. We found strong support for a monophyletic Dalbergia oliveri and encourage that this name is used consistently in Indochina. The CITES-listed Dalbergia cochinchinensis was successfully identified, and a species-specific assay can be developed from the data generated in this study for the identification of illegally traded timber. We suggest that the use of DNA barcoding is integrated into the work flow during floristic studies and at national herbaria in the region, as this could significantly increase the number of identified specimens and improve knowledge about species distributions.

Occupational toxic epidermal necrolysis associated with dalbergia cochinchinensis: a retrospective comparative study of eight cases in China.[Pubmed: 25944249]

Occupational toxic epidermal necrolysis (TEN) related to Dalbergia cochinchinensis has seldom been reported in the past. Its clinical characteristic needs to be investigated. This study reports eight cases of such disease in China.

Mutational analysis in the glycone binding pocket of Dalbergia cochinchinensis β-glucosidase to increase catalytic efficiency toward mannosides.[Pubmed: 23583451]

Dalcochinase and Abg are glycoside hydrolase family 1 β-glucosidases from Dalbergia cochinchinensis Pierre and Agrobacterium sp., respectively, with 35% sequence identity. However, Abg shows much higher catalytic efficiencies toward a broad range of glycone substrates than dalcochinase does, possibly due to the difference in amino acid residues around their glycone binding pockets. Site-directed mutagenesis was used to replace the amino acid residues of dalcochinase with the corresponding residues of Abg, generating three single mutants, F196H, S251V, and M369E, as well as the corresponding three double mutants and one triple mutant. Among these, the F196H mutant showed increases in catalytic efficiency toward almost all glycoside substrates tested, with the most improved catalytic efficiency being a 3-fold increase for hydrolysis of p-nitrophenyl β-D-mannoside, suggesting a preferred polar residue at this position and consistent with the presence of histidine at this position in two other GH1 glycosidases from barley and rice that prefer β-mannosides. In addition, the M369E mutation resulted in a small increase in catalytic efficiency for cleavage of p-nitrophenyl β-D-galactoside. By contrast, the multiple mutants were up to 8-fold less efficient than the recombinant wild-type dalcochinase, and displayed primarily antagonistic interactions between these residues. Thus, differences in catalytic efficiency between dalcochinase and Abg are therefore not primarily due to differences in the residues that directly contact the substrate, but derive largely from contributions from more remote residues and the overall architecture of the active site.

Functional and structural differences between isoflavonoid beta-glycosidases from Dalbergia sp.[Pubmed: 17998137]

Among isoflavonoid beta-glucosidases from Dalbergia species, that from Dalbergia nigrescens hydrolyzes isoflavonoid-7-O-beta-D-apiosyl-1,6-beta-D-glucosides more efficiently, while Dalbergia cochinchinensis beta-glucosidase (dalcochinase) hydrolyzes its rotenoid glycoside substrate, dalcochinin beta-d-glucoside (I), more efficiently. A cDNA encoding a glycosylated beta-glucosidase with 81% identity with dalcochinase was cloned from D. nigrescens seeds, and its protein (Dnbglu2) expressed in Pichia pastoris. Purified Dnbglu2 hydrolyzed the D. nigrescens natural substrates dalpatein 7-O-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyranoside (II) and dalnigrein 7-O-beta-d-apiofuranosyl-(1-->6)-beta-D-glucopyranoside (III) at 400- and 5000-fold higher catalytic efficiency (k(cat)/K(m)) than I. Dalcochinase was mutated at two amino acid residues, A454S and E455G, that are homologous to previously described substrate binding residues and differ from the corresponding residues in Dnbglu2. The double mutant showed 4- and 6.8-fold increases in relative activity toward II and III, respectively. However, this activity was only 3% that of Dnbglu2 beta-glucosidase, indicating other determinants are important for isoflavonoid diglycoside hydrolysis.

Hydrolysis of soybean isoflavonoid glycosides by Dalbergia beta-glucosidases.[Pubmed: 17311399]

Two beta-glucosidases from the legumes Dalbergia cochinchinensis and Dalbergia nigrescens were compared for their ability to hydrolyze isoflavonoid glycosides from soybean. Both D. nigrescens and D. cochinchinensis beta-glucosidases could hydrolyze conjugated soybean glycosides, but D. nigrescens beta-glucosidase hydrolyzed both conjugated and nonconjugated glycosides in crude soybean extract more rapidly. The kinetic properties Km, kcat, and kcat/Km of the Dalbergia beta-glucosidases toward conjugated isoflavonoid glycosides, determined using high-performance liquid chromatography, confirmed the higher efficiency of the D. nigrescens beta-glucosidase in hydrolyzing these substrates. The D. nigrescens beta-glucosidase could also efficiently hydrolyze isoflavone glycosides in soy flour suspensions, suggesting its application to increase free isoflavones in soy products.

Expression and purification of dalcochinase, a beta-glucosidase from Dalbergia cochinchinensis Pierre, in yeast and bacterial hosts.[Pubmed: 16814564]

The coding sequence of the mature dalcochinase, a beta-glucosidase from Dalbergia cochinchinensis Pierre, was cloned and expressed in various systems. Expression in Escherichia coli resulted in an insoluble protein, which could be made soluble by co-expression with bacterial chaperonin GroESL. However, the enzyme had no activity. Recombinant expression in Pichia pastoris and Saccharomyces cerevisiae yielded an active enzyme. Dalcochinase was expressed under methanol induction in P. pastoris, since this was much more efficient than constitutive expression in P. pastoris or in S. cerevisiae. Addition of 0.5% casamino acids to the culture medium stabilized the pH of the culture and increased the protein yield by 3- to 5-folds. Insertion of a polyhistidine-tag either after the N-terminal alpha factor signal sequence or at the C-terminus failed to assist in purification by immobilized metal-ion affinity chromatography (IMAC) due to post-translational processing at both termini. A new construct of dalcochinase with an N-terminal truncation following the propeptide and eight histidine residues enabled its purification by IMAC, following hydrophobic interaction chromatography. The purified recombinant dalcochinase was apparently composed of differently post-translationally modified forms, but had kinetic properties and pH and temperature optima comparable to natural dalcochinase. The procedures reported here overcome the limitation in enzyme supply from natural sources, and allow further studies on structure-function relationships in this enzyme.

Phenolic constituents from Dalbergia cochinchinensis.[Pubmed: 12932142]

Three new phenolic compounds (1-3), along with five known phenolics, 4'-hydroxy-2'-methoxychalcone (4), latinone (5), dalbergiphenol (6), 7-hydroxyflavanone, and dalbergin (7), have been isolated from the stems of Dalbergia cochinchinensis. The structures of 1-3 were established by spectroscopic techniques including 1D and 2D NMR methods. The inhibitory activity against testosterone 5 alpha-reductase, which causes androgen-dependent diseases, was also examined for selected compounds.