Synthesis and biological activity of abscisic acid esters

16 ABA esters including 11 new compounds were prepared by two different esterification routes. All the structures of ABA esters were confirmed by ¹H NMR, ¹³C NMR and HRMS. Their biological activity and hydrolysis stability were investigated. Fortunately, there were 15 and 9 compounds which displayed much better or nearly the same inhibition activity for rice seedling growth and Arabidopsis thaliana seed germination compared to ABA, respectively. Especially, compounds 2d and 2g showed better biological activities than ABA in the three tests. Moreover, we found that chemical hydrolysis ability of the esters in vitro had little relationship to their biological activity.     

The biological activity of complex esters of saccharose and higher fatty acids

Sucrose/fatty acid ethers from Astasia longa culture have been studied. Biological activity of different ethers has been studied on calf kidney cells. The activity depends on the lipid component of the ethers. The highest stimulation of cell layer formation was observed with ethers of sucrose and polyunsaturated fatty acids.     

Synthesis and biological activity of 2-hydroxynicotinoyl-serine-butyl esters related to antibiotic UK-3A

Novel 2-hydroxynicotinoyl-serine-butyl esters have been synthesized. Three-step reactions from l-serine by esterification with n-butanol, amidation with 2-hydroxynicotinic acid and esterification with the corresponding carboxylic acids gave AD-1, AD-2 and AD-3. The toxicity level of esters were determined by Brine shrimp assay, and antibiotic activity was tested against Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Candida albicans. AD-3 showed greater activity as a growth inhibitor of B. subtilis and S. aureus compared to Antimycin A₃.     

Autoxidation of polyunsaturated esters in water: chemical structure and biological activity of the products

When polyunsaturated esters or fatty acids are dispersed for long periods in water in the presence of air, water-soluble substances are formed in great variety. Because these short-chain products are constantly eluted by the aqueous phase and are consequently not available for further reaction in the oil phase, many intermediates of classical autoxidation can be isolated and identified. The identification of several of these compounds is described. Some of the peroxidic and nonperoxidic autoxidation products show biochemical activity-in particular, inhibition of glycolysis and of respiration during incubation with tumor cells in vitro. Minimal inhibitory concentrations of pure, isolated products have been determined for Ehrlich ascites tumor cells. Synthetic short-chain (C(4)-C(10)) hydroxylated alpha,-unsaturated aldehydes have been shown to have this action and also to cause morphological changes in these cells which quickly lead to their death. Normal cells are not affected. Possible therapeutic use of these compounds in the treatment of malignant neoplasms is discussed.     

Long-acting contraceptive agents: The influence of pharmaceutical formulation upon biological activity of esters of norethisterone

17β-esters of norethisterone (17α-ethynyl-17β-hydroxyestr-4-en-3-one) have been formulated as aqueous microcrystalline suspensions and oily solutionsfor administration to rats to assess the length of progestogenic activity. Results show that, for some of the esters, the rate-controlling step in prolonging activity is the rate of drug release from the injected formulation. For these esters, when formulated as suspensions, it is proposed that crystal size and form will have a critical effect upon duration of estrus suppression. The influence of crystal form has been demonstrated with the 4-(butoxy)phenylacetate ester for which two different crystal forms have been identified. The lower melting point, more soluble crystal form shows marked prolongation of action, whereas the other form is ineffective.     

Preparation and biological evaluation of some 1,2-O-isopropylidene-D-hexofuranose esters

The synthesis and biological evaluation of some new glycose esters bearing the 1,2-O-isopropylidene-d-hexofuranose functionality and belonging to the 3-O-acyl-d-allose and 6-O-acyl-d-glucose series are reported. When the results concerning cell growth inhibition are compared, it appears that the 6-O-acyl-d-glucose derivatives are more active than the 3-O-acyl-d-allose compounds. Within both 6-O-acyl-d-glucose and 3-O-acyl-d-allose derivatives, butyric esters displayed the highest inhibitory effects. Inhibition of cell growth is not associated with high induction levels of erythroid differentiation, despite the fact that pivaloates induce erythroid differentiation to an extent similar to that exhibited by previously reported molecules [Bioorg. Med. Chem. Lett.1999, 9, 3153-3158].     

Production and biological function of volatile esters in Saccharomyces cerevisiae

The need to understand and control ester synthesis is driven by the fact that esters play a key role in the sensorial quality of fermented alcoholic beverages like beer, wine and sake. As esters are synthesized in yeast via several complex metabolic pathways, there is a need to gain a clear understanding of ester metabolism and its regulation. The individual genes involved, their functions and regulatory mechanisms have to be identified. In alcoholic beverages, there are two important groups of esters: the acetate esters and the medium-chain fatty acid (MCFA) ethyl esters. For acetate ester synthesis, the genes involved have already been cloned and characterized. Also the biochemical pathways and the regulation of acetate ester synthesis are well defined. With respect to the molecular basis of MCFA ethyl ester synthesis, however, significant progress has only recently been made. Next to the characterization of the biochemical pathways and regulation of ester synthesis, a new and more important question arises: what is the advantage for yeast to produce these esters? Several hypotheses have been proposed in the past, but none was satisfactorily. This paper reviews the current hypotheses of ester synthesis in yeast in relation to the complex regulation of the alcohol acetyl transferases and the different factors that allow ester formation to be controlled during fermentation.     

Comparative chemical and biological hydrolytic stability of homologous esters and isosteres

Esters are one of the major functional groups present in the structures of prodrugs and bioactive compounds. Their presence is often associated with hydrolytic lability. In this paper, we describe a comparative chemical and biological stability of homologous esters and isosteres in base media as well as in rat plasma and rat liver microsomes. Our results provided evidence for the hydrolytic structure lability relationship and demonstrated that the hydrolytic stability in plasma and liver microsome might depend on carboxylesterase activity. Molecular modelling studies were performed in order to understand the experimental data. Taken together, the data could be useful to design bioactive compounds or prodrugs based on the correct choice of the ester subunit, addressing compounds with higher or lower metabolic lability.     

Leishmanicidal activity of amino acid and peptide esters

Amino acid and dipeptide esters kill intracellular and isolated L. amazonensis amastigotes. Several o f the compounds also restrict the growth o f mouse lesions after intralesional administration. However, the esters are known to be toxic in vitro for monocytes and certain lymphoid cells. Michel Rabinovitch surveys the mechanisms o f the leishmanicidal activity, describes some structure--activity relationships, and discusses strategies for the design of compounds more selective for the parasite.     

Identification and quantitation of fatty acid ethyl esters in biological specimens

Fatty acid ethyl esters, recently described as enzymatic products of nonoxidative ethanol metabolism in the heart, may represent a mediator or marker of ethanol-induced organ pathology such as alcoholic cardiomyopathy. This study was designed to develop a method for the extraction, quantitation, and definitive identification of fatty acid ethyl esters formed both in biological specimens and during enzymatic incubations. First, several potential sources of error were identified and characterized. Tissue extraction with alcohols led to the time, temperature, and concentration-dependent nonenzymatic formation of fatty acid alcohol esters. Contamination of both substrates, [14C]ethanol and 14C-fatty acid, used to measure enzymatically mediated fatty acid ethyl ester synthesis, could be removed by purification. Accurate quantitation of fatty acid ethyl esters in tissue was achieved using acetone as an extraction solvent, after which isolated lipids were thin-layer chromatographed on silica gel developed with an apolar solvent system (petroleum ether:diethyl ether:acetic acid, 75:5:1). Gas chromatography and mass spectroscopy identified individual fatty acid ethyl esters. The reproducibility of this assay was high, as assessed by quintuplicate determinations of fatty acid ethyl esters formed in liver and heart homogenates, a method with standard deviations 4 to 11% of the mean.     

Scabrosin esters and derivatives: chemical derivatization studies and biological evaluation

Several derivatives of the natural scabrosin esters were synthesized in order to elucidate the structural features present, which are responsible for the biological activities. The studies demonstrate that full anti-proliferative activities of the scabrosin esters, both the carboskeleton core as well as the ability to form the dithiol and/or the disulfide linkage of the epidithiopiperazine-2,5-dione are required. The presence of the epoxide rings on the scabrosin esters do not contribute to the observed biological activities.     

The synthesis and antiherpetic activity of acyclovir phosphonate esters

Alkyl esters of acyclovir phosphite, alkoxycarbonylphosphonate, ethoxycarbonylmethylphosphonate, and aminocarbonylphosphonate were synthesized. Most of them were shown to inhibit the replication of type 1 herpes simplex virus in Vero cell culture. The stability in phosphate buffer and human blood serum was studied for several of the derivatives. A correlation between the stability and antiviral activity of the synthesized compounds is discussed. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 6; see also http://www.maik.ru.     

Isolation and biological activity of frankiamide

An antibiotic produced by the symbiotic actinomycete Frankia strain AiPs1 was isolated from culture broth using optimized thin-layer chromatography and high-performance liquid chromatography (HPLC) methods. The novel compound that was isolated, dubbed frankiamide, displayed antimicrobial activity against all 14 Gram-positive bacterial strains and six pathogenic fungal strains tested. The pathogenic actinomycete Clavibacter michiganensis and the ooymycete Phytophthora were especially susceptible. In addition to displaying antimicrobial activity, frankiamide also strongly inhibited ⁴⁵Ca²⁺ fluxes in clonal rat pituitary GH₄C₁ tumor cells and was comparable to a frequently used calcium antagonist, verapamil hydrochloride. The results of HPLC analysis, supported by both nuclear magnetic resonance and mass spectroscopy studies, showed that frankiamide has a high affinity for Na⁺ ions. Journal of Industrial Microbiology & Biotechnology (2001) 27, 62–66. Received 26 February 2001/ Accepted in revised form 01 June 2001     

Synthesis and biological evaluation of 2-alkoxycarbonylallyl esters as potential anticancer agents

The reaction of carboxylic acids with Baylis-Hillman reaction derived α-bromomethyl acrylic esters readily provide 2-(alkoxycarbonyl)allyl esters in good to excellent yields. These functionalized allyl esters have been evaluated for their cell proliferation inhibition properties against breast cancer (MDA-MB-231 and 4T1) and pancreatic cancer (MIAPaCa-2) cell lines to explore their potential as anticancer agents. Several of the synthesized derivatives exhibit good potency against all three cancer cell lines. Our structure activity relationship (SAR) studies on 2-carboxycarbonyl allyl esters indicate that substituted aromatic carboxylic acids provide enhanced activity compared to substituted aliphatic carboxylic acid analogs. Di- and tri-allyl esters derived from di-and tri-carboxylic acids exhibit higher inhibition of cell proliferation than mono esters. Further SAR studies indicate that the double bond in the 2-(alkoxycarbonyl)allyl ester is required for its activity, and there is no increase in activity with increased chain length of the alkoxy group. Two lead candidate compounds have been identified from the cell proliferation inhibition studies and their preliminary mechanism of action as DNA damaging agents has been evaluated using epifluorescence and western blot analysis. One of the lead compounds has been further evaluated for its systemic toxicity in healthy CD-1 mice followed by anticancer efficacy in a triple negative breast cancer MDA-MB-231 xenograft model in NOD-SCID mice. These two in vivo studies indicate that the lead compound is well tolerated in healthy CD-1 mice and exhibits good tumor growth inhibition compared to breast cancer drug doxorubicin.