Three new trimeric stilbenes from Gnetum gnemon. (1/11)

Three stilbene trimers (gnemonols D, E, F) were isolated from the root of Gnetum gnemon. The structures were determined by spectroscopic analysis. In addition, the antioxidant activity of the compounds on lipid peroxide inhibition and super oxide scavenging activity were also investigated.  (+info)

Gnetol as a potent tyrosinase inhibitor from genus Gnetum. (2/11)

Gnetol (2,3',5',6-tetrahydroxy-trans-stilbene), a naturally occurring compound particularly found in the genus Gnetum, had a strong inhibitory effect on murine tyrosinase activity. Gnetol (IC50, 4.5 microM) was stronger than kojic acid (IC50, 139 microM) as a standard inhibitor for murine tyrosinase activity. Moreover, gnetol significantly suppressed, melanin biosynthesis in murine B16 melanoma cells.  (+info)

Horizontal gene transfer from flowering plants to Gnetum. (3/11)

Although horizontal gene transfer is well documented in microbial genomes, no case has been reported in higher plants. We discovered horizontal transfer of the mitochondrial nad1 intron 2 and adjacent exons b and c from an asterid to Gnetum (Gnetales, gymnosperms). Gnetum has two copies of intron 2, a group II intron, that differ in their exons, nucleotide composition, domain lengths, and structural characteristics. One of the copies, limited to an Asian clade of Gnetum, is almost identical to the homologous locus in angiosperms, and partial sequences of its exons b and c show characteristic substitutions unique to angiosperms. Analyses of 70 seed plant nad1 exons b and c and intron 2 sequences, including representatives of all angiosperm clades, support that this copy originated from a euasterid and was horizontally transferred to Gnetum. Molecular clock dating, using calibrations provided by gnetalean macrofossils, suggests an age of 5 to 2 million years for the Asian clade that received the horizontal transfer.  (+info)

Preparation on oligostilbenes of isorhapontigenin by oxidative coupling reaction. (4/11)

Four new compounds 1-4 were obtained from an oxidative coupling reaction of (E)-isorhapontigenin using FeCl(3) as oxidant. Their structures and stereochemistry were determined on the basis of spectroscopic evidence [UV, IR, MS, (1)H-, (13)C-NMR, NOE and 2D NMR], and their possible formation mechanisms were also discussed, respectively.  (+info)

Isolation and biomimetic synthesis of anti-inflammatory stilbenolignans from Gnetum cleistostachyum. (5/11)

One new stilbenolignan, gnetucleistol F (1), and four known stilbenolignans, gnetofuran A (2), lehmbachol D (3), gnetifolin F (4) and gnetumontanin C (5) were isolated from the lianas of Gnetum cleistostachyum C. Y. CHENG (Gnetaceae). Their structures and relative configurations were determined by means of spectroscopic evidence. Compounds 1, 2, 3 and 4 were synthesized for the first time on the basis of their biogenetic pathway, and their possible biomimetical synthetic mechanisms were discussed. The pharmacological activities of all stilbenolignans have been tested. Among them, 1, 2, 3, 4 and 5 showed moderate inhibitory activities on TNF-alpha and 1 also showed potent inhibitory activity on malondialdehyde.  (+info)

Chloroplast genome (cpDNA) of Cycas taitungensis and 56 cp protein-coding genes of Gnetum parvifolium: insights into cpDNA evolution and phylogeny of extant seed plants. (6/11)

Phylogenetic relationships among the 5 groups of extant seed plants are presently unsettled. To reexamine this long-standing debate, we determine the complete chloroplast genome (cpDNA) of Cycas taitungensis and 56 protein-coding genes encoded in the cpDNA of Gnetum parvifolium. The cpDNA of Cycas is a circular molecule of 163,403 bp with 2 typical large inverted repeats (IRs) of 25,074 bp each. We inferred phylogenetic relationships among major seed plant lineages using concatenated 56 protein-coding genes in 37 land plants. Phylogenies, generated by the use of 3 independent methods, provide concordant and robust support for the monophylies of extant seed plants, gymnosperms, and angiosperms. Within the modern gymnosperms are 2 highly supported sister clades: Cycas-Ginkgo and Gnetum-Pinus. This result agrees with both the "gnetifer" and "gnepines" hypotheses. The sister relationships in Cycas-Ginkgo and Gnetum-Pinus clades are further reinforced by cpDNA structural evidence. Branch lengths of Cycas-Ginkgo and Gnetum were consistently the shortest and the longest, respectively, in all separate analyses. However, the Gnetum relative rate test revealed this tendency only for the 3rd codon positions and the transversional sites of the first 2 codon positions. A PsitufA located between psbE and petL genes is here first detected in Anthoceros (a hornwort), cycads, and Ginkgo. We demonstrate that the PsitufA is a footprint descended from the chloroplast tufA of green algae. The duplication of ycf2 genes and their shift into IRs should have taken place at least in the common ancestor of seed plants more than 300 MYA, and the tRNAPro-GGG gene was lost from the angiosperm lineage at least 150 MYA. Additionally, from cpDNA structural comparison, we propose an alternative model for the loss of large IR regions in black pine. More cpDNA data from non-Pinaceae conifers are necessary to justify whether the gnetifer or gnepines hypothesis is valid and to generate solid structural evidence for the monophyly of extant gymnosperms.  (+info)

Inhibitory effect of gnetin C, a resveratrol dimer from melinjo (Gnetum gnemon), on tyrosinase activity and melanin biosynthesis. (7/11)

Tyrosinase is the key enzyme involved in melanogenesis. The aim of this study was to investigate the in vitro inhibitory effects of gnetin C, a resveratrol dimer isolated from melinjo (Gnetum gnemon) seeds, on tyrosinase activity and melanin biosynthesis in murine B16 cells. The inhibitory activities of gnetin C and resveratrol were shown to be almost equal against tyrosinase and melanin biosynthesis in the cells. The IC(50) values of gnetin C activity against tyrosinase and melanin biosynthesis were 7.0 and 7.6 microM, respectively, whereas resveratrol demonstrated IC(50) values of 7.2 and 7.3 microM, respectively. These results indicated that gnetin C inhibited melanogenesis, in a manner similar to that of resveratrol, by inhibiting tyrosinase and may therefore function as a new skin-whitening agent. However, the direct effects of gnetin C and resveratrol on murine tyrosinase activities were not equal. The IC(50) value of resveratrol was 10.1 microM, while gnetin C only exhibited a 25.2% enzyme inhibition at 16 microM. The IC(25) values for gnetin C and resveratrol were 15.5 and 4.0 microM, respectively. Therefore, it is suggested that the effects of gnetin C may be due to mechanisms other than the direct inhibition of tyrosinase activity.  (+info)

Cuspidans A and B, two new stilbenoids from the bark of Gnetum cuspidatum. (8/11)

Cuspidan A (1), a new stilbene sestermer consisting of a resveratrol, an oxyresveratrol, and a 3,5-dihydroxyphenylmethanol constituent units and cuspidan B (2), a new tri-cyclic stilbene monomer were isolated from the bark of Gnetum cuspidatum. The structures and configurations of 1 and 2 were elucidated on the basis of 2D-NMR correlations.  (+info)