Two new monoterpene glycosides and trypanocidal terpenoids from Dracocephalum kotschyi

From the whole plant of Dracocephalum kotschyi BOISS., two new monoterpene glycosides (9, 10), together with seven known terpenoids and a phytosterol (1-8), were isolated. Their structures were determined to be limonen-10-al (1), geranial (2), neral (3), beta-sitosterol (4), oleanolic acid (5), ursolic acid (6), p-mentha-8-en-1,2-diol (7), colosolic acid (8), limonen-10-ol 10-O-beta-D-glucopyranoside (9), and limonen-10-ol 10-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranoside (10). Compounds 1 (3.1 microM), 2 (3.1 microM), 3 (3.1 microM), 5 (6.2 microM), 6 (6.2 microM), and 8 (6.2 microM) were effective against epimastigotes of Trypanosoma cruzi.     

Application of the TORO technique of 1H NMR to the structural analysis of cyclic peptide isomers having a slightly distorted symmetry from C2

The extended TORO technique was applied to the structural analysis of endo-D-Tyr-gramicidin S, cyclo(-Val-Orn-Leu-D-Phe-D-Tyr-Pro-Val-Orn-Leu-D-Phe-Pro-), which has a slightly distorted symmetry from C2, by the insertion of D-Tyr and equivalent alpha-proton chemical shifts in the 1H NMR spectrum. All NMR signals of the two dominant isomers of this antibiotic with trans-trans prolines were determined by using the extended TORO technique with TOCSY and ROESY spectra. This technique is generally applicable for distinguishing overlapped signals of alpha- and amide protons from the main chains of peptides.     

Scillapersicene: a new homoisoflavonoid with cytotoxic activity from the bulbs of Scilla persica HAUSSKN

The phytochemical investigation of Scilla persica HAUSSKN bulbs led to the isolation of a novel homoisoflavonoid that named Scillapersicene (1) and identified as 3-(3′,4′-dihydroxybenzylidene)-8-hydroxy-5,7-dimethoxychroman-4-one along with five known homoisoflavonoids 2–6, whose structures were elucidated using HRFAB-MS, 1D and 2D NMR spectroscopic data. The known compounds were identified as 3-(3′,4′-dihydroxybenzyl)-5,8-dihydroxy-7-methoxychroman-4-one (2), 3,9-dihydro-autumnalin (3), autumnalin (4), 3-(3′,4′-dihydroxybenzylidene)-5,8-dihydroxy-7-methoxychroman-4-one (5) and scillapersicone (6). All compounds obtained, expect 2 and 4, showed strong cytotoxic activity against AGS cell line. The toxicity on AGS cell line was measured by 1, 3, 5 and 6 with IC₅₀ values of 8.4, 30.5, 10.7 and 24.2 μM, respectively. In addition, the physico-chemical properties of these natural compounds were optimised using density functional method (B3LYP) with standard 6-311+G* basis set. These natural products have low-energy gaps between the first ionisation potentials and highest occupied molecular orbital. In conclusion, the low-energy gap could cause reason for cytotoxic activity of homoisoflavonoids.     

Infrared spectra of (HCOOH)(2) and (DCOOH)(2) in rare gas matrices: a comparative study with gas phase spectra

Infrared absorption spectra of (HCOOH)(2) and (DCOOH)(2) in solid argon, krypton, and xenon matrices have been measured and each fundamental band has been assigned. Spectra in Ar and Kr matrices showed notable splitting in contrast to those in Xe, which suggests a difference in structure of the trapping sites. A comparison with the reported jet-cooled spectra has shown that vibrational structures of the spectra of (HCOOH)(2) and (DCOOH)(2) in the O-H stretching region are preserved in the matrices. On the other hand, the C-O stretching band of (HCOOH)(2) shows a drastic change upon matrix isolation, wherein the Fermi-triad feature observed in gas phase [F. Ito, Chem. Phys. Lett. 447, 202 (2007)] could not be identified. No substantial change of the vibrational structure has been found for matrix-isolated (DCOOH)(2). The differences of the vibrational structures in the matrix-isolation spectra and in the jet-cooled spectra have been qualitatively accounted for using the idea of anharmonic couplings among "matrix-shifted harmonic states."     

Synthesis of an Anthraquinone-Bridged bis(terpyridine) Ligand and its Use in the Stepwise Fabrication of Complex Oligomer Wires on Gold

A new bis(terpyridine) ligand with an anthraquinone linker was synthesized. Stepwise coordination reactions at the gold surface using this ligand gave homo-metal oligomer wires up to pentamer, [ n FeL ₁ ] (n = 1–5), and hetero-metal oligomer wires with ferrocene as the terminal group, [1FeL ₁ 1FeL ₂ Fc] . Electrochemical properties of these modified electrodes were examined.     

Thermodynamics for the Formation of Double‐Stranded DNA–Single‐Walled Carbon Nanotube Hybrids

For the first time, the thermodynamics are described for the formation of double‐stranded DNA (ds‐DNA)–single‐walled carbon nanotube (SWNT) hybrids. This treatment is applied to the exchange reaction of sodium cholate (SC) molecules on SWNTs and the ds‐DNAs d(A)₂₀–d(T)₂₀ and nuclear factor (NF)‐κB decoy. UV/Vis/near‐IR spectroscopy with temperature variations was used for analyzing the exchange reaction on the SWNTs with four different chiralities: (n,m)=(8,3), (6,5), (7,5), and (8,6). Single‐stranded DNAs (ss‐DNAs), including d(A)₂₀ and d(T)₂₀, are also used for comparison. The d(A)₂₀–d(T)₂₀ shows a drastic change in its thermodynamic parameters around the melting temperature (T_m) of the DNA oligomer. No such T_m dependency was measured, owing to high T_m in the NF‐κB decoy DNA and no T_m in the ss‐DNA.