Synthesis and biological activities of 4-chloroindole-3-acetic acid and its esters

4-Chloroindole-3-acetic acid (4-Cl-IAA) and its esters were synthesized from 2-chloro-6-nitrotoluene as the starting material. The biological activities of 4-CI-IAA and its esters were determined by four bioassays. Except for the tert-butyl ester, 4-Cl-IAA and its esters had stronger elongation activity toward Avena coleoptiles than had indole-3-acetic acid. The biological activities of the methyl, ethyl and allyl esters were as strong as the activity of the free acid. All the esters, except for the tert-butyl, inhibited Chinese cabbage hypocotyl growth more than the free acid did, and all the esters induced severe swelling and formation of numerous lateral roots in black gram seedlings even at a low concentration. Furthermore, adventitious root formation was strongly promoted in Serissa japonica cuttings by all the esters. The root formation-promoting activities of the ethyl and allyl esters were about three times the value for indole-3-butyric acid which is used to promote and accelerate root formation in plant cuttings.     

1,3-Dinitrates of cyclooxygenase metabolites of endocannabinoid 2-arachidonoylglycerol. Synthesis and properties

The 1,3-Dinitrates of glycerol esters of natural prostaglandins that are the cyclooxygenase metabolites of 2-arachidonoylglycerol, an endogenous ligand of cannabinoid receptors, were synthesized for the first time. Four methods of synthesis of these esters were developed via the activation of a carboxyl group and their chemical and pharmacological properties were investigated. The esters exhibit a more selective pharmacological spectrum of activities in comparison with the corresponding natural prostaglandins: some types of myotropic activity were enhanced, while others were loosened. 1,3-dinitroglycerol esters act as vasodilators, whereas the majority of natural prostaglandins act as vasoconstrictors. The observed changes result from the introduction of an NO-releasing fragment into prostaglandin molecule.     

Enzymatic synthesis and anti-oxidative activities of plant oil-based ascorbyl esters in 2-methyltetrahydrofuran-containing mixtures

Ascorbyl fatty acid esters are commercially interesting fat-soluble antioxidants. In this work, enzymatic synthesis of ascorbyl esters from less expensive and readily available plant oils, and their anti-oxidative activities are described. Among the immobilized lipases tested, Candida antarctica lipase B was the best for the synthesis of plant oil-based ascorbyl esters. The enzyme showed much better catalytic performances in the binary mixtures of biomass-based 2-methyltetrahydrofuran (MeTHF) and t-butanol than the previously preferred t-butanol. The conversions of 70–73% were obtained under the optimal reaction conditions after 24?h, with the unsaturated fatty acid esters (oleate and linoleate, 80–90%) as the major products. The immobilized lipase kept the relative activity of 80% after reuse for 6 batches in MeTHF-containing system. Besides, anti-oxidative activities of plant oil-based ascorbyl esters and ascorbic acid were comparable, which could remove α,α-diphenyl-β-picrylhydrazyl (DPPH) free radical of >87%.     

The enzymic deacylation of phospholipids and galactolipids in plants. Purification and properties of a lipolytic acyl-hydrolase from potato tubers

An enzyme preparation that catalyses the deacylation of mono- and di-acyl phospholipids, galactosyl diglycerides, mono- and di-glycerides has been partially purified from potato tubers. The preparation also hydrolyses methyl and p-nitrophenyl esters and acts preferentially on esters of long-chain fatty acids. Triglycerides, wax esters and sterol esters are not hydrolysed. The same enzyme preparation catalyses acyl transfer reactions in the presence of alcohols and also catalyses the synthesis of wax esters from long-chain alcohols and free fatty acids. Gel filtration, DEAE-cellulose chromatography and free-flow electrophoresis failed to achieve any separation of the acyl-hydrolase activities towards different classes of acyl lipids (phosphatidylcholine, monogalactosyl diglyceride, mono-olein, methyl palmitate and p-nitrophenyl palmitate) or any separation of these activities from a major protein component. For each class of lipid the acyl-hydrolase activity was subject to substrate inhibition, was inhibited by relatively high concentrations of di-isopropyl phosphorofluoridate and the pH responses were changed by Triton X-100. The hydrolysis of phosphatidylcholine was stimulated 30-40-fold by Triton X-100. The specific activities of the potato enzyme with galactolipids were at least 70 times higher than those reported for a homogeneous galactolipase enzyme purified from runner bean leaves. The possibility that a single lipolytic acyl-hydrolase enzyme is responsible for the deacylation of several classes of acyl lipid is discussed.     

Thiols as myeloperoxidase-oxidase substrates.

Nine low-Mr thiols were compared with regard to their ability to function as myeloperoxidase-oxidase substrates under conditions where no auto-oxidation of the thiols could be observed. The methyl and ethyl esters of cysteine were found to be about twice as active as cysteamine at pH 7.0, in terms of increased O2 consumption. Cysteine itself was poorly active, whereas glutathione, N-acetylcysteine and penicillamine were completely inactive as myeloperoxidase-oxidase substrates under these conditions. The structure-activity relationships indicated that both a free thiol and free amino group were required for peroxidase-oxidase activity, and also that a free carboxy group abolished activity. In analogy with cysteamine, the activities of both cysteine esters were inhibited by superoxide dismutase (less than 5 micrograms/ml) and by catalase and not by the hydroxyl-radical scavenger mannitol. In contrast with cysteamine, the activities of both cysteine esters were stimulated more than 2-fold by high concentrations (greater than 5 micrograms/ml) of superoxide dismutase. The activities of both cysteine esters exhibited broad pH optima at pH 7. A mechanism for the myeloperoxidase-oxidase oxidation of the cysteine esters is proposed, which is partly different from that previously proposed for cysteamine.     

Design, synthesis, biological evaluation, and comparative Cox1 and Cox2 docking of p-substituted benzylidenamino phenyl esters of ibuprofenic and mefenamic acids

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently associated with gastric mucosal and renal adverse reactions, related to inhibition of cyclooxygenase1 (Cox1) in tissues where prostaglandins exert physiological effects. This led us to develop a set of ibuprofenic acid and mefenamic acid esters, namely: 4-((4-substituted benzylidene)amino)phenyl 2-(4-isobutylphenyl)propanoate and 4-((4-substituted benzylidene)amino)phenyl 2-((2,4-dimethylphenyl)amino)benzoate analogs, which were synthesized by condensation of the corresponding acids with Schiff's bases [4-(4-substituted benzylideneamino)phenols] involving dicyclohexyl carbodiimmide (DCC) as mild dehydrating agent. The main objective is to reduce the GIT toxicity associated with acute and chronic NSAIDs use. Anti-inflammatory, analgesic as well as ulcerogenic activities of the prepared esters were evaluated in vivo and compared with that of ibuprofen as reference standard in all screenings, involving the carrageenan induced paw oedema model and hot plate method. Most of the synthesized esters showed remarkable analgesic and anti-inflammatory activities. Interestingly, all of the compounds were found to be non-ulcerogenic under the tested conditions. This evidence have suggested that modification of the carboxyl function of representative NSAIDs results in retained or enhanced anti-inflammatory and analgesic activities with reduced ulcerogenic potential. Additionally, a comparative AutoDock study into Cox 1 and Cox2 has been done involving both of rigid and flexible docking for potential selectivity of our compounds within different Cox enzymes and to find out the binding orientation of these novel esters into their binding site. Some of the newly prepared aforementioned compounds showed considerable more Cox2 over Cox1 binding affinities by flexible docking better than rigid one.     

Prostaglandin E and F levels in mouse epidermis are increased by tumor-promoting phorbol esters

After topical application of tumor-promoting phorbol esters, immunoreactive prostaglandins E and F in mouse epidermis were increased several-fold over basal levels. The increases were doubled by 3 hours and lasted until 5 days after phorbol ester treatment. The activities of various phorbol esters for increasing epidermal prostaglandin levels paralleled the tumorpromoting activities of these compounds. Topical pretreatment with nonsteroidal anti-inflammatory drugs inhibited the effect of phorbol esters on epidermal prostaglandin levels.     

New prodrugs of Adefovir and Cidofovir

New Adefovir (PMEA) prodrugs with a pro-moiety consisting of decyl or decyloxyethyl chain bearing hydroxyl function(s), hexaethyleneglycol or a (5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl unit were prepared starting from the tetrabutylammonium salt of the phosphonate drug and an appropriate alkyl bromide or tosylate. Analogously, two esters of Cidofovir [(S)-HPMPC] bearing a hexaethyleneglycol moiety were prepared. The activity of the prodrugs was evaluated in vitro against different virus families. A loss in the antiviral activities of the hydroxylated decyl or decyloxyethyl esters and hexaethyleneglycol esters of PMEA against human immunodeficiency virus (HIV) and herpesviruses [including herpes simplex virus (HSV), varicella-zoster virus (VZV), and human cytomegalovirus (CMV)] occurred in comparison with the parent compound. On the other hand, the (5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl ester of PMEA showed significant activities against HIV and herpesviruses. (S)-HPMPC prodrugs exhibited anti-cytomegalovirus activities in the same range as the parent drug, whereas the anti-HSV and anti-VZV activities were one- to seven-fold lower than that of Cidofovir.     

Turnover of cholesteryl esters of plasma lipoproteins in the rat

Turnover of individual classes of cholesteryl esters (classified on the basis of the degree of unsaturation of the fatty acid moiety) in rat plasma lipoproteins and liver was studied after the administration of mevalonic acid-5-(3)H and mevalonic acid-2-(14)C. The relative turnover rate was greatest in the d < 1.019 lipoproteins, with monoenes > saturated = dienes > tetraenes. In the d > 1.063 lipoproteins, all cholesteryl esters had slower turnover rates, but tetraenes = pentaenes > dienes > monoenes = saturated. Comparisons of specific activities of individual cholesteryl ester classes of liver subcellular fractions and lipoproteins suggest that the d < 1.019 lipoprotein cholesteryl esters are synthesized from newly synthesized cholesterol in the liver and are rapidly released into this lipoprotein. Tetraenoic cholesteryl esters, however, may originate from esterification of free cholesterol in plasma. Tetraenoic esters are formed from cholesterol in plasma during incubation or ultracentrifugation unless a thiol-reacting or alkylating agent is added. Failure to add such a reagent to plasma results in erroneous specific activities. In the adrenal, relative rates of synthesis of cholesteryl esters are monoenes = dienes > tetraenes > trienes = pentaenes > saturated. It is concluded that cholesteryl ester turnover in the rat, as opposed to man, is determined not only by the particular lipoprotein class but also by the fatty acid moiety of the ester.     

Synthesis and cytotoxic activities of new fatty acid esters of 20(S)-protopanaxadiol

In order to find new lead compounds with antitumour activies, thirteen new fatty acid esters of 20(S)-protopanaxadiol (PPD) were synthesized using oleoyl chloride or fatty acids and N,N'-dicyclohexylcarbodiimide (DCC). Their cytotoxic activities were tested using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] method, and the structure-activity relationships between the fatty acid esters of PPD and their cytotoxic activities are discussed.     

Neutral and acid retinyl ester hydrolases associated with rat liver microsomes: relationships to microsomal cholesteryl ester hydrolases

We recently reported the presence of a neutral, bile salt-independent retinyl ester hydrolase (REH) activity in rat liver microsomes and showed that it was distinct from the previously studied bile salt-dependent REH and from nonspecific carboxylesterases (Harrison, E. H., and M. Z. Gad. 1989. J. Biol. Chem. 264: 17142-17147). We have now further characterized the hydrolysis of retinyl esters by liver microsomes and have compared the observed activities with those catalyzing the hydrolysis of cholesteryl esters. Microsomes and microsomal subfractions enriched in plasma membranes and endosomes catalyze the hydrolysis of retinyl esters at both neutral and acid pH. The acid and neutral REH enzyme activities can be distinguished from one another on the basis of selective inhibition by metal ions and by irreversible, active site-directed serine esterase inhibitors. The same preparations also catalyze the hydrolysis of cholesteryl esters at both acid and neutral pH. However, the enzyme(s) responsible for the neutral REH activity can be clearly responsible for the neutral REH activity can be clearly differentiated from the neutral cholesteryl ester hydrolase(s) on the basis of differential stability, sensitivity to proteolysis, and sensitivity to active site-directed reagents. These results suggest that the neutral, bile salt-independent REH is relatively specific for the hydrolysis of retinyl esters and thus may play an important physiological role in hepatic vitamin A metabolism. In contrast to the neutral hydrolases, the activities responsible for hydrolysis of retinyl esters and cholesterol esters at acid pH are similar in their responses to the treatments mentioned above. Thus, a single microsomal acid hydrolase may catalyze the hydrolysis of both types of ester.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis of N-hydroxycinnamoyl amide derivatives and evaluation of their anti-oxidative and anti-tyrosinase activities

Twelve N-hydroxycinnamoyl amino acid amide ethyl esters (CAES) were synthesized by using l-amino acid ethyl ester hydrochloride and corresponding cinnamic acid (ferulic acid, acetylferulic acid and caffeic acid) as raw materials in the presence of a catalytic amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide-hydrochloride (EDC) and 1-hydroxybenzotriene (HOBt). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activities of CAES were evaluated. The anti-tyrosinase activities of N-feruloyl amino acid ethyl esters and the hydroxyl (OH) free radical scavenging activities of N-caffeoyl amino acid ethyl esters were also examined. DPPH free radical scavenging activity was shown in all CAES, of which N-caffeoyl amino acid ethyl esters demonstrated higher radical scavenging activity than N-feruloyl amide derivatives, and (E) -N-(caffeic acid)-l-glycinate ethyl ester (c₅) had the strongest ability to scavenge free radicals with an IC₅₀ value of 18.6 µM. The acetylferuloyl amino acid esters exhibited the highest tyrosinase inhibition activity among the tested amides.     

Characterisation of steryl esterase activities in commercial lipase preparations

Triglycerides, steryl esters, resin acids, free fatty acids and sterols are lipophilic extractives of wood (commonly referred to as pitch or wood resin) and have a negative impact on paper machine runnability and quality of paper. Thus, enzymes capable of modifying these compounds would be potential tools for reducing pitch problems during paper manufacture. In this work, 19 commercial lipase preparations were tested for their ability to degrade steryl esters, which may play a significant role in the formation and stabilisation of pitch particles. Six lipase preparations were shown to be able to degrade steryl esters. Lipase preparations of Pseudomonas sp., Chromobacterium viscosum and Candida rugosa were shown to have the highest steryl esterase activities. The enzymes were able to hydrolyse steryl esters totally in the presence of a surfactant (Thesit). Up to 80% of the steryl esters were degraded in aqueous dispersion. Preliminary characterisation of the enzymatic activities revealed that the lipase preparation of Pseudomonas sp. could be the most potential enzyme in industrial applications. The steryl esterase activity of this preparation was stable over a broad pH range and the enzyme was able to act efficiently at pH 6-10 and at temperatures up to 70 degrees C.     

Comparative study on digestive lipase activities on the self emulsifying excipient Labrasol, medium chain glycerides and PEG esters

Labrasol is a lipid-based self-emulsifying excipient used in the preparation of lipophilic drugs intended for oral delivery. It is mainly composed of PEG esters and glycerides with medium acyl chains, which are potential substrates for digestive lipases. The hydrolysis of Labrasol by porcine pancreatic extracts, human pancreatic juice and several purified digestive lipases was investigated in the present study. Classical human pancreatic lipase (HPL) and porcine pancreatic lipase, which are the main lipases involved in the digestion of dietary triglycerides, showed very low levels of activity on the entire Labrasol excipient as well as on separated fractions of glycerides and PEG esters. On the other hand, gastric lipase, pancreatic lipase-related protein 2 (PLRP2) and carboxyl ester hydrolase (CEH) showed high specific activities on Labrasol. These lipases were found to hydrolyze the main components of Labrasol (PEG esters and monoglycerides) used as individual substrates, whereas these esters were found to be poor substrates for HPL. The lipolytic activity of pancreatic extracts and human pancreatic juice on Labrasol(R) is therefore mainly due to the combined action of CEH and PLRP2. These two pancreatic enzymes, together with gastric lipase, are probably the main enzymes involved in the in vivo lipolysis of Labrasol taken orally.     

Mung bean nuclease: mode of action and specificity vs synthetic esters of 3'-nucleotides

Mung bean nuclease hydrolyzes synthetic esters of 3′-nucleotides to nucleosides and phosphate esters; esters of 2′-nucleotides, and 2′→ 5′ internucleotide linkages, are resistant. Esters of ribonucleotides are cleaved at 100-fold the rate for deoxyribonucleotides, the increased rate being due to presence of the 2′-hydroxyl and not to differences in conformation. Introduction of a 5′-substituent leads to a 3-fold increase in rate. The rates of hydrolysis vary up to 10-fold with the nature of the base, in the order adenine > hypoxanthine > uracil; and up to 6-fold with the nature of the ester radical. This form of cleavage of esters of 3′-nucleotides is also characteristic for nuclease-3′-nucleotidase activities from potato tubers and wheat, suggesting that one type of enzyme is responsible for all these activities.     

Esterification of cholesterol and lipid-soluble vitamins by human pancreatic carboxyl ester hydrolase

Human pancreatic carboxyl ester hydrolase is shown to catalyse the esterification of cholesterol and lipid-soluble vitamins A, E and D3 with oleic acid. The acitivity requires the presence of bile salts, and the trihydroxylated or the 3 alpha, 7 alpha dihydroxylated bile salts are better activators than the 3 alpha, 12 alpha dihydroxylated bile salts. The hydrolyzing and synthetizing activities of human pancreatic carboxyl ester hydrolase are separated by a large pH range since the synthesis of cholesterol esters is optimal at pH 5.25 and the hydrolysis of cholesterol and vitamin E esters is optimal at pH 8.0. From the comparison of the catalytic constants determined for the hydrolyzing and synthetizing activities and from the pH dependence of the two activities, it appears that human carboxyl ester hydrolase plays an important part in the intestinal lumen. The role of the enzyme in the esterification of cholesterol and lipid-soluble vitamins is questionable.     

Effect of d-Limonene and related compounds on bile flow and biliary lipid composition in rats and dogs

d-Limonene enhanced bile flow in rats and dogs with a dose response correlation. The choleretic activity was much higher in the metabolites of d-limonene such as p-mentha-1,8-dien-10-ol, p-menth-1-ene-8,9-diol and p-mentha-1,8-dien-6-ol than d-limonene, and this suggested that the choleretic activity of d-limonene was attributable at least in part to its metabolites.The choleretic activities of esters of p-menth-1-ene-8,9-diol with acetic acid, propionic acid, stearic acid, palmitic acid, linoleic acid, benzoic acid, salicylic acid, α-naphthylacetic acid and nicotinic acid were also investigated in rats. Among these compounds, acetate, propionate and nicotinate possessed considerable, but lesser activities than the original diol. In dogs, however, the choleretic activity of p-menth-l-ene-8,9-diol acetate and propionate was much higher than that of original diol, suggesting that the choleretic activity of these esters is attributable to the esters themselves.d-Limonene decreased the ratio of biliary bile salts and phospholipids to cholesterol, whereas p-menth-l-ene-8,9-diol increased it.     

Cholesteryl ester oxidation products in atherosclerosis

Lipid oxidation products are formed at sites of increased oxidant stress and have been shown to accumulate in atherosclerotic lesions. Although recent studies have focused on the formation and metabolism of oxidized lipids, very little is known about their biological activities and possible (patho)physiological functions. Oxidation of cholesteryl esters containing unsaturated fatty acids leads to the formation of hydroperoxides that are either reduced to alcohols or degrade into biologically active "core-aldehydes". In this review, the mechanisms of formation and metabolic fate of oxidized cholesteryl esters, their occurrence, as well as possible biological activities are discussed. Based on the current knowledge, cholesteryl ester oxidation leads to the formation of biologically active substances, which could actively contribute to the progression of atherosclerotic lesions and their resulting complications.     

Resolution, purification and characterization of the orthophosphate releasing activities from fracture callus calcifying cartilage.

Callus calcifying cartilage alkaline phosphatase was resolved by DEAE-cellulose column chromatography into two distinct phsophatase activities. The phosphatase activity which was eluted first from the column, (phosphatase I), was active towards a variety of phosphate esters, sodium pyrophosphatase and several linear polyphosphates, while the second phosphatase activity , (phosphatase II), was active toward simple phosphate esters but not towards sodium pyrophosphate and linear oligo or polyphosphates. All the phosphate esters, sodium pyrophosphate and polyphosphates at higher concentrations were inhibitory for phosphatase I. The modulating effects of magnesium, calcium, zinc and other phosphatase modulators have been investigated. Both phosphatases from callus calcifying cartilage were found to be substrates of neuraminidase with sialic acid as the product. Besides the difference in their specificity, the phosphatases were found to be immunologically different and to have different molecular weights, strong indication that they are different enzymes.