Phenothiazine-bridged cyclic porphyrin dimers as high-affinity hosts for fullerenes and linear array of C60 in self-assembled porphyrin nanotube.

Free-bases and a nickel(II) complex of phenothiazine-bridged cyclic porphyrin dimers bearing self-assembling 4-pyridyl groups (M2-Ptz-CPDPy(OCn); M = H2 or Ni, OCn = OC6 or OC3) at opposite meso-positions have been prepared as host molecules for fullerenes. The free-base dimer (H4-Ptz-CPDPy(OC6)) includes fullerenes with remarkably high association constants such as 3.9 ± 0.7 × 10(6) M(-1) for C60 and 7.4 ± 0.8 × 10(7) M(-1) for C70 in toluene. This C60 affinity is the highest value ever among reported receptors composed of free-base porphyrins. The nickel dimer (Ni2-Ptz-CPDPy(OC6)) also shows high affinities for C60 (1.3 ± 0.2 × 10(6) M(-1)) and C70 (over 10(7) M(-1)). In the crystal structure of the inclusion complex of C60 within H4-Ptz-CPDpy(OC3), the C60 molecule is located just above the centers of the porphyrins. The two porphyrin planes are almost parallel to each other and the center-to-center distance (12.454 Å) is close to the optimal separation (∼12.5 Å) for C60 inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C-H···N hydrogen bonds between porphyrin ß-CH groups and pyridyl nitrogens as well as π-π interactions of the pyridyl groups. The C60 molecules are linearly arranged in the inner channel of this nanotube.

Assay of angiotensin I-converting enzyme-inhibiting activity based on the detection of 3-hydroxybutyric acid.

Hypertension and related diseases afflict millions of individuals worldwide, and many investigations of angiotensin I-converting enzyme (ACE) activity have been carried out. Most of these have used hippuryl-histidyl-leucine (HHL) as a substrate for ACE reaction with considerable interferences. Here we propose the use of a new substrate, 3-hydroxybutyrylglycyl-glycyl-glycine (3HB-GGG) for the screening of ACE inhibitors. Under the actions of ACE and aminoacylase, 3HB-GGG is cleaved into amino acids (Gly and Gly-Gly) and 3-hydroxybutyric acid (3HB). The assay conditions were optimized and applied to monitor the ACE inhibitory activity in terms of 3HB measured using an F-kit. Under the optimum assay parameters-ACE (0.2 U/ml) and aminoacylase (172 kU/ml) incubated with 3HB-GGG (3.4 mg/ml) at 37 degrees C for 30 min-the Gly-Gly and Gly cleaved from 3HB-GGG by enzymes was able to be identified, affirming the feasibility of substituting 3HB-GGG for the conventional substrate HHL. In addition, the current method was more sensitive, accurate, rapid, and convenient than the conventional method.

Flow injection determination of xanthine oxidase inhibitory activity and its application to food samples.

The enzyme xanthine oxidase (XOD) has been recognized as a key enzyme causing oxidative injury to tissues by ischemia-reperfusion. For this reason, XOD inhibitor, which effectively suppresses this enzyme, plays an important role in the inhibition of many diseases related to reactive oxygen species (ROS). In order to screen XOD inhibitors rapidly and conveniently, a novel assay using flow injection analysis (FIA) was proposed in the present investigation. To optimize the practical FIA system, we studied the effect of the reagent concentrations and the flow condition on the enzymatic reaction, and then selected the optimum condition as follows: 200-mU/ml XOD concentration, 0.5-mM xanthine concentration, 0.5-ml/min flow rate, and 2-m mixing coil length. Under this condition, a typical XOD inhibitor quercetin was determined in the concentration range 0.1 - 1.5 mM at a sampling frequency of 10 samples/h. Using the optimized FIA method, we determined the XOD inhibitory activity of some food samples: onions, apples and teas, which are the high sources of flavonoids known as the potential XOD inhibitors. Among these samples, tea leaves showed the highest activity, the second was onions and the lowest was apples. Based on the result of the assay, not only quercetin, but also other components in investigated samples, contributed to the XOD inhibitory activity.

Synthesis of diversely functionalized hexahydropyrrolo[2,3-b]indoles using domino reactions, olefination, isomerization and Claisen rearrangement followed by reductive cyclization.

Hexahydropyrrolo[2,3-b]indoles 6 were synthesized in five steps from indolin-3-one 8 by a general and efficient method, in which elements of molecular diversity were readily added onto the 3a-position of the pyrrolo[2,3-b]indole ring system. Horner-Wadsworth-Emmons reaction of 2-allyloxyindolin-3-ones 7, derived from indolin-3-one 8 and a variety of allylic alcohols, smoothly proceeded with successive Claisen rearrangement to give the corresponding 3-allyl-3-cyanomethylindolin-2-ones 15. Indolin-2-ones 15 were converted into pyrrolo[2,3-b]indoles 6 using partial hydrolysis followed by reductive cyclization with LiAlH(4). Synthesis of N-methylated pyrrolo[2,3-b]indole derivatives 23 and 26 is also described.

Preparation of 9-hydroxy grayanotoxin derivatives and their acute toxicity in mice.

Novel 9alpha and 9beta-hydroxy grayanotoxin II derivatives were prepared by photo-sensitized oxygenation of iso-grayanotoxin II and oxidation of grayanotoxin II tetraacetate with selenium dioxide respectively. The lethal dosage of 9alpha and 9beta-hydroxy grayanotoxin II were lower than that of grayanotoxin II. In addition, the lethal dosage of 9beta-hydroxy-dihydro grayanotoxin II was higher than that of dihydro grayanotoxin II.