Two novel cucurbitacins, neocucurbitacins A and B, from the Brazilian folk medicine "Buchinha" (Luffa operculata) and their effect on PEBP2alphaA and OCIF gene expression in a human osteoblast-like Saos-2 cell line

Two novel cucurbitacins designated as neocucurbitacins A (1), possessing inhibitory activity of polyoma enhancer binding protein 2alphaA (PEBP2alphaA) and osteoclastogenesis-inhibitory factor (OCIF) gene expression in human osteoblast-like cells, and B (2) were isolated from the fruit of Luffa operculata. Their structures have been determined by extensive spectroscopic investigation.

A novel sesterterpenoid, nitiol, as a potent enhancer of IL-2 gene expression in a human T cell line, from the Peruvian folk medicine "Hercumpuri" (Gentianella nitida)

A novel sesterterpenoid designated as nitiol (1), possessing enhancement activity of IL-2 gene expression in a human T cell line, was isolated from the Peruvian folk medicine "Hercampuri" (Gentianella nitida). The structure was elucidated by extensive spectroscopic investigation.

Screening for bioactive compounds targeting the cellular signal transduction pathway using an RT-PCR-based bioassay system

A novel bioassay system based on RT-PCR has been established to search for biologically active compounds which can modulate the expression of genes encoding important regulatory proteins. Changes in target mRNA level in the treated cell cultures were quantitatively determined by competitive PCR using internal standard DNA. The compounds discovered using this bioassay will be useful tools to elucidate the mechanisms of cellular signaling guiding the expression of the target genes. As the first application of the new bioassay strategy, the expression of the interleukin-2 gene in Jurkat cells, a human T cell line, was investigated. Screening of several crude drugs used in traditional Chinese medicines demonstrated that the aqueous acetone extract of Coptidis Rhizoma enhanced the expression of the interleukin-2 gene by about 5-fold as compared to the control.

Cloning of chalcone-flavanone isomerase cDNA from Pueraria lobata and its overexpression in Escherichia coli

Chalcone-flavanone isomerase (CHI) cDNA was isolated from Pueraria lobata by combination of cDNA library screening using Phaseolus vulgaris CHI cDNA as a probe and polymerase chain reaction techniques. Analysis of nucleotide sequence of the cloned cDNA revealed a 675-bp open reading frame encoding a 225-amino-acid polypeptide with a molecular weight of 23,803 Da. The CHI cDNA coding region was cloned into pET-3d expression vector and successfully overexpressed in Escherichia coli cells as active CHI enzyme. The recombinant CHI was then purified to apparent homogeneity by DEAE-cellulose column chromatography. Replacement of Cys-119 with Ala was carried out by site-directed mutagenesis and the result that the mutant CHI showed CHI enzyme activity confirmed that Cys-119 is not involved in the CHI catalytic active site.

cDNA and genomic DNA clonings of chalcone synthase from Pueraria lobata

Four cDNAs encoding chalcone synthase (CHS), the key enzyme in flavonoid biosynthesis, were isolated from Pueraria lobata cells challenged with yeast extract elicitor using bean CHS cDNA as a probe. The longest clone contained a complete open reading frame of 1170 bp which would predict a protein of about 43 kDa. The others were not full-length clones. Using isolated cDNA as a probe, Southern blot hybridization of genomic DNA fragments revealed the presence of multiple CHS genes in the P. lobata genome. We cloned and sequenced one CHS genomic clone, gCHS14, whose 5' untranslated region showed homology with the bean CHS gene CHS15 and included the several reported sequences characteristic of stress response.

Isolation, sequence and bacterial expression of a cDNA for chalcone synthase from the cultured cells of Pueraria lobata

cDNA clones for chalcone synthase (CHS) of Pueraria lobata cultured cells were isolated by screening the cDNA library using CHS cDNA of Phaseolus vulgaris as a probe. Analysis of nucleotide sequences of the cloned cDNA revealed a 1170-bp open reading frame that encoded a 390-amino acid polypeptide with an Mr of 43,000. The full-length cDNA was cloned into the expression vector pT7-7. CHS activity was found in the crude extracts of transformed E. coli after induction and two protein bands of ca. 43 and 34 kd were hybridized with anti-persley CHS antiserum.

Reaction mechanism of oxidative rearrangement of flavanone in isoflavone biosynthesis

Microsomes that were prepared from elicitor-treated Pueraria lobata cell cultures catalyzed the conversion of liquiritigenin, a flavanone, into daidzein, an isoflavone. The reaction was resolved into two steps. 2, 7, 4'-Trihydroxyisoflavonone was formed as a major product when liquiritigenin was incubated with carefully washed microsomes in the presence of NADPH. The structure of 2, 7, 4'-trihydroxyisoflavanone was confirmed by mass and 1H NMR spectroscopies. The enzyme responsible for this rearrangement reaction is a cytochrome P-450-dependent monooxygenase. Upon treatment with a soluble enzyme fraction 2, 7, 4'-trihydroxyisoflavone yielded daidzein quantitatively. The incorporation of 18O from 18O2 into the 2-hydroxy group of 2, 7, 4'-trihydroxyisoflavanone was demonstrated by the shift of molecular ion in its mass spectrum. Based on these observations a new reaction mechanism, hydroxylation associated with 1,2-migration, is proposed for the oxidative rearrangement reaction catalyzed by the cytochrome P-450 enzyme of Pueraria lobata.