A study of nuclear prenylation of 2,4-dihydroxy phenyl benzyl ketone: Syntheses of linear and angular 6″,6″-dimethyl pyrano-isoflavones,and their 2-methyl and 2-phenyl analogues

2,4-Dihydroxyphenyl benzyl ketone (I) condenses with 2-methyl but-3-en-2-ol in the presence of boron trifluoride etherate to afford a mixture of 3-C-, 5-C- and 3,5-di C C-prenyl derivatives separable by chromatography. The above mixture without the 5-C-prenyl but with the 4-O-prenyl derivative results when ketone I is treated with prenyl bromide in the presence of methanolic potash. 3-C-(III a) and 5-C-(IV) prenyl derivatives undergo ready oxidative cyclization with DDQ to yield the corresponding pyrano derivatives VIII and XII respectively which form good starting materials for various isoflavone condensations. Thus both linear and angular 6″,6″-dimethyl pyrano-isoflavones and their 2-methyl and 2-phenyl analogues have been synthesized.     

Role of partially flocculated sols in emulsion stability

Summary The stability of emulsion of Toluene in water stabilized by partially flocculated ferric hydroxide sol has been studied. The size of the emulsion droplets as determined by size frequency analysis is found to be of 1.1 μ radius. The flocculation studies were carried out haemocytometrically at different amount of electrolytes and at different p_H values. The electrokinetic potential ‘ζ’ was determined micro-electrophoretically at different amounts of electrolytes and also at different p_H's. In the case of tri and tetra valent anions the charge reversal was observed. In the light of the D.V.O. theory the interaction energy profiles were drawn and 2–6 kT deep secondary minima obtained showing thereby the occurrence of reversible flocculation. Degree of aggregation has been calculated theoretically at different values of ‘A’ and the value of A was found to be 1.0×10⁻¹² erg to fit the value of degree of aggregation obtained haemocytometrically. The charge densities and binding parameters have also been calculated.     

Delivery of Benzoporphyrin Derivative, a Photosensitizer, into Atherosclerotic Plaque of Watanabe Heritable Hyperlipidemic Rabbits and Balloon-Injured New Zealand Rabbits

Abstract— In this study we compared the plasma distribution and arterial accumulation of a photosensitizer, benzoporphyrin derivative (BPD), in two models of atherosclerosis: the spontaneous lesions of the Watanabe heritable hyperlipidemic (WHHL) rabbit and induced lesions of the balloon-injured, cholesterol-fed New Zealand white (NZW) rabbit. Selective uptake and retention of a photosensitizer by the abnormal portion of a vessel is a necessity in order for photodynamic therapy to become a successful modality for inhibition of intimal hyperplasia, selective removal of atherosclerotic tissue or imaging of diseased arteries. Liposome-based formulations were compared to freshly isolated native low density lipoprotein (LDL) and acetylated-LDL (Ac-LDL) as delivery vehicles for BPD. Plasma distribution of the photosensitizer was analyzed by KBr density gradient ultracentrifuga-tion. Although the delivery vehicle influenced plasma distribution immediately postinjection, BPD subsequently partitioned according to the plasma concentration of the lipoproteins. Photosensitizer level in plaque and normal artery specimens was determined by ethyl acetate extraction and spectrofluorometric measurement. The measurement of BPD in normal and atherosclerotic arterial tissue demonstrated a selective accumulation in atherosclerotic tissue. Preassociation with LDL and Ac-LDL enhanced accumulation of BPD in atherosclerotic tissue when compared with normal artery (mean ratios of 2.8 and 4.1 were achieved, respectively). These results indicate that the preferential uptake of BPD by atherosclerotic plaque can be enhanced by preassociation with plasma lipoproteins, suggesting that light activation could lead to a highly selective destruction of diseased vascular tissue.     

Synthesis of (±) lupinifoun, di-o-methyl xanthohumol and isoxanthohumol and related compounds

Nuclear prenylation of naringenin (7) with 2-methylbut-3-en-2-ol in the presence of boron trifluoride etherate gives a mixture of 6-C-prenyl-(11), 8-C-prenyl-(15) and 6,8-di-C-prenyl-(8) derivatives. On formic acid cyclisation, 11 yielded two monodihydropyrans (12 and 13), but 15 afforded only one viz 16; similarly 8 formed the bisdihydropyran 10. Methylation of 8-C-prenyl naringenin (15) with Me₂SO₄ resulted in the formation of di-O-methyl derivatives of xanthohumol (22) and isoxanthohumol (23).

Cyclodehydrogenation of 6,8-di-C-prenyl-naringenin (8) with DDQ gave a mono-C-prenyl-2,2-dimethylpyran (1) corresponding to (±) lupinifolin. The angular isomer (2) was also formed. The structure of natural flemichin-B therefore needs further consideration. Similarly, cyclodehydrogenation of 6-C-(11)- and 8-C-prenyl-(15) naringenins afforded the corresponding linear (24) and angular (25) derivatives which have been characterized by conversion into known chalcones 26 and 27 by O-methylation.     

ENERGETICS OF DNA REPAIR IN UV-IRRADIATED PERIPHERAL BLOOD LEUKOCYTES FROM CHRONIC MYELOID LEUKAEMIA PATIENTS

Abstract— The relationship between energy metabolism and UV-induced (251 nm) DNA repair has been investigated in leukocytes obtained from peripheral blood of chronic myeloid leukaemia patients. Energy supply was modulated by using inhibitors of respiratory (antimvcin-A) and glycolytic (2-deoxy-o-glucose and other glucose analogues) pathways for adenosine-triphosphatc (ATP) production. DNA repair was measured by the unscheduled DNA synthesis technique. Parameters of energy metabolism like glucose utilization. lactate production and ATP content of cells. were measured under similar experimental conditions. The observations made indicate the following results: (1) ATP for DNA repair can be supplied by the respiratory and/or by the glycolytic pathway. (2) In the absence of respiration, the rate of glycolysis bears a linear correlation with DNA repair. (3) A minimum threshold rate of ATP-production is necessary for DNA repair.     

High-order one-step P-stable methods for the numerical integration of periodic initial value problems

Using Lobatto nodes, one-step methods of order six and eight have been obtained for the second-order differential equation y″ = f(x, y), y(x₀) = y₀, y′(x₀) = y′₀. The methods are shown to be P-stable. If

, then at each integration step a system of dimension 3s, 4s, respectively, has to be solved. The numerical results, for two problems, obtained by using these methods are given in the end.     

Spectrophotometric determination of ascorbic acid in pharmaceuticals by background correction and flow injection

Background correction has been shown to be an effective and indispensable modification in the spectrophotometric determination of ascorbic acid. The decomposition of ascorbic acid in pharmaceutical samples was carried out by incubation with sodium hydroxide to give products that were insensitive to ultraviolet light. The rapid oxidation in air of ascorbic acid, especially in dilute solutions, was avoided by the use of the flow injection principle for spectrophotometric determination and by employing a carrier stream of an anti-oxidizing nature consisting of 6 micrograms ml(-1) of 2-mercaptoethanol in 0.25% sulphuric acid. The optimized method with a single channel manifold made use of a carrier stream flow rate of 1.1 ml min(-1), an injection volume of 50 microl, a delay coil of 50 cm (0.5 mm i.d.) and detection at 245 nm. The throughput was at least 180 injections h(-1). The proposed flow injection method yielded results for the analysis of 0-20 micrograms ml(-1) of ascorbic acid that were 99-102% (relative standard deviation 0.6% or better) in agreement with those produced by comparable methods involving titration with iodine, chloranil or 2,6-dichlorophenolindophenol [4-(2,6-dichloro-4-hydroxyphenylimino)cyclohexa-2,5-dieno ne], and high-performance liquid chromatography. When the agreement was not good (as low as 14% with respect to the method being compared), this was traced to the presence of substances which are known to interfere in one or other of the methods of comparison.