Subergane‐Type Sesquiterpenes from Gorgonian Coral Subergorgia suberosa with Antibacterial Activities

A new subergane‐type sesquiterpene, named epoxysubergorgic acid ( 1 ), along with seven known sesquiterpenes, were isolated from the gorgonian coral Subergorgia suberosa. The structure of the new compound was determined by extensive spectroscopic analyses. The previously uncertain absolute configuration of the known analogues 2 – 6 was determined on the basis of CD, Mosher's method, and through chemical conversions. All compounds were evaluated for antibacterial activities.     

Suberosanones A – C,New Metabolites Possessing Cyclopentenone System from the South China Sea Gorgonian Coral Subergorgia suberosa

Two unusual novel bicyclic lactones, suberosanones A and B ( 1 and 2 , resp.), characterized by the co‐occurrence of cyclopentenone and butanolide rings within the same molecule, along with one tricyclic cyclopentenone derivative, suberosanone C ( 3 ), were isolated from the South China Sea gorgonian coral Subergorgia suberosa. Their structures were unambiguously established by detailed spectroscopic analyses (NMR, IR, and HR‐MS). The absolute configurations of 1 and 2 were determined by quantum‐chemical calculations using the time‐dependent density‐functional theory (TDDFT) method. All compounds showed neither antifouling activity against Balanus amphitrite larvae settlement nor antibacterial activity against a panel of bacterial strains at concentrations up to 25 μg/ml.     

Oxidations of erogorgiaene in pseudopterosin biosynthesis

Pseudopterosins are potent anti-inflammatory diterpene glycosides initially isolated from the gorgonian coral Pseudopterogorgia elisabethae. In continuation of pathway elucidation studies focused on this family of terpenes, we report the isolation of 7-hydroxyerogorgiaene and 7,8-dihydroxyerogorgiaene from P. elisabethae and confirm the intermediacy of these compounds in pseudopterosin biosynthesis by in vitro incubation experiments with these metabolites in radiolabeled form.     

Thiazolidin-4-Ones as Potential Antimicrobial Agents: Experimental and In Silico Evaluation

Herein, we report computational and experimental evaluations of the antimicrobial activity of twenty one 2,3-diaryl-thiazolidin-4-ones. All synthesized compounds exhibited an antibacterial activity against six Gram-positive and Gram-negative bacteria to different extents. Thus, the MIC was in the range of 0.008–0.24 mg/mL, while the MBC was 0.0016–0.48 mg/mL. The most sensitive bacterium was S. Typhimurium, whereas S. aureus was the most resistant. The best antibacterial activity was observed for compound 5 (MIC at 0.008–0.06 mg/mL). The three most active compounds 5, 8, and 15, as well as compound 6, which were evaluated against three resistant strains, MRSA, P. aeruginosa, and E. coli, were more potent against all bacterial strains used than ampicillin. The antifungal activity of some compounds exceeded or were equipotent with those of the reference antifungal agents bifonazole and ketoconazole. The best activity was expressed by compound 5. All compounds exhibited moderate to good drug-likeness scores ranging from −0.39 to 0.39. The docking studies indicated a probable involvement of E. coli Mur B inhibition in the antibacterial action, while CYP51 inhibition is likely responsible for the antifungal activity of the tested compounds. Finally, the assessment of cellular cytotoxicity of the compounds in normal human MRC-5 cells revealed that the compounds were not toxic.     

海洋放线菌S592次级代谢产物及其体外抑菌活性研究

对海洋放线菌S592的次级代谢产物以及体外抑菌活性进行研究.将菌株S592进行大量发酵,采用色谱方法对菌株发酵产物进行分离纯化,通过波谱技术对所获单体化合物进行结构鉴定,并测定化合物的体外抑菌活性.从海洋放线菌S592中分离得到6个化合物,含2个螺环抗生素lobophorin类化合物,1个环肽类化合物,2个苯甲酰胺类化...     

Synthesis and antibacterial activity of the metabolites of 9-fluoro-6,7-dihydro-8-(4-hydroxy-1-piperidyl)-5-methyl-1-oxo-1H,5H- benzo[i,j]quinolizine-2-carboxylic acid (OPC-7251)

The metabolites of 9-fluoro-6,7-dihydro-8-(4-hydroxy-1-piperidyl)-5-methyl-1-oxo-1H,5H- benzo[i,j]quinolizine-2-carboxylic acid (OPC-7251) (1), which has a potent antibacterial activity against gram-positive bacteria, characteristically Propionibacterium acnes, were synthesized to confirm their structures and to examine their antibacterial activity. The structures of three major metabolites (2, 3a and 4) were identified by means of comparison with the synthetic compounds. The antibacterial activity of the metabolites (2, 3a and 4) was found to be lower than that of 1.     

4-烷氧基苯甲醛-4-氨基安替比林希夫碱的合成及抑菌活性

报道了4-氨基安替比林与4-烷氧基苯甲醛缩合反应生成希夫碱的合成和抑菌活性,分子结构由1HNMR、IR和元素分析表征;抑菌活性测定结果表明,化合物(5a,5d,5e,5f,5g)对金黄色葡萄球菌、大肠杆菌、枯草杆菌、黑霉菌、青霉菌(抑菌环直径15.3 ～ 21.70 mm)均有较好的抑菌活性,其中化合物(5f)对黑霉菌(抑菌环直径26.20 mm)有优良的抑菌活性.     

Antibacterial and antioxidant activity of naphthofuranquinones from the twigs of tropical mangrove Avicennia officinalis

Abstract

Mangrove plants are endowed with various biologically active compounds which have potent antibacterial and antioxidant properties. In present study, a bioactivity-guided fractionation for antibacterial and antioxidant active metabolites from the twigs of Avicennia officinalis collected from Kuala Selangor Nature Park, Selangor, Malaysia gave 13 major fractions. The antibacterial activity of A. officinalis fractions using well-diffusion showed strong selectivity on the Gram-positive bacteria (Staphylococcus epidermidis, S. aureus and Bacillus subtilis) with minimum inhibition concentration (MIC) values of 0.156-5.00?mg/mL. However, no antibacterial activities were observed on the Gram-negative bacteria (Vibrio cholera, Enterobacter cloacae and Escherichia coli). The active antibacterial fractions were further isolated using several chromatographic techniques to give two naphthofuranquinones, namely, avicenol C (1) and stenocarpoquinone B (2). Meanwhile, the antioxidant activity of A. officinalis fractions were evaluated using DPPH radical scavenging assay exhibited low antioxidant activities. Molecular structure of the naphthofuranquinones was elucidated using 1?D and 2?D NMR spectroscopy.     

Gas chromatographic-mass spectrometric method for analysis of a pyrimido-s-triazine and some of its metabolites in dog urine.

3-Phenylpyrimido-[3,4-a]-s-triazines exhibit antiparasitic, antibacterial and antifungal activity. In order to study the metabolism of these heterocycles, 9,9-diethyl-3-phenyl-6,8-dioxo-2,3,4,5,6,7,8,9-octahydropyrimido[3 ,4-a]-s- triazine (TZ) was administered to dogs. Three potential metabolites were synthesized, and these models were identified and quantified with gas chromatography-mass spectrometry. The heterobicyclic compounds, TZ and its hydroxy derivative, underwent thermal degradation under chromatographic conditions. Dog urine spiked with the model metabolites was extracted, and the substances were quantified. The urine of dogs treated with TZ was studied, and two of the potential metabolites were recovered, identified and quantified.     

Synthesis and biological activities of novel ethers of quinolinone linked with coumarins

Abstract  

A series of new ethers of quinolinone linked with different substituted coumarins and benzofurans were synthesized from 4-(bromomethyl)quinolinones. All newly synthesized compounds were screened for their in vitro antibacterial and antifungal activities. Most of the compounds with chloro substitution at the C-6 or C-7 position in quinolinone showed potent antibacterial and antifungal activities. In pharmacological evaluations, some of these chloroquinolinones also showed 70–77% inhibition of inflammation after 8 h, whereas the other compounds showed 51–55% inhibition. Most of the compounds showed potent analgesic activity compared to the standard and control. The structures of all newly synthesized compounds were characterized by elemental analysis, IR, ¹H NMR, ¹³C NMR, and EI-MS.     

Synthesis and antibacterial activity of C-2(S)-substituted pleuromutilin derivatives

<正>In order to probe the effect of C-2(S)-substituted groups in the antibacterial activity,a series of novel C-2(S)-substituted pleuromutilin analogues of SB-225586 were synthesized and evaluated for their in vitro antibacterial activity.The results of antibacterial activities indicated that C-2(S)-substituted pleuromutilin derivatives retained appreciable antibacterial activity,and the 2-fluorination compounds 6a and 6b are more potent than the corresponding 2-hydroxylation analogues 7a and 7b.     

Perspectives on the structural and biosynthetic interrelationships between oxygenated furanocembranoids and their polycyclic congeners found in corals

Macrocyclic and polycyclic ‘cembranoid’ diterpenes are one of the most widespread groups of natural products that are found in the marine milieu. The macrocyclic cembranoids are linked to each other by a network of oxygenation processes, which often climax with the formation of furano- and furanobutenolide-based macrocyclic cembranoids commonly found in gorgonian and soft corals. These macrocycles are then prone to oxidative rearrangements, photochemical ring contraction, and transannular cyclisations amongst others, leading to a plethora of novel and architecturally attractive marine metabolites. Although there is a dearth of knowledge about the enzymes that trigger some of the steps in their biosynthesis, speculations are rife. In this personal perspective we have examined many of the structural relationships within oxycembranoids and their relatives isolated from corals. This has allowed us to speculate on the likely biosynthetic interrelationships between structurally similar metabolites, and then propose some likely key carbon-to-carbon bond forming reactions that are followed in vivo in linking macrocyclic cembranoids to their polycyclic congeners. Biomimetic synthesis studies, which vindicate some of the biosynthetic speculations, are interweaved in the discussion.     

Inhibitory study of some novel Schiff base derivatives on Staphylococcus aureus by microcalorimetry

The effect of a series of novel Schiff base compounds on Staphylococcus aureus was studied by microcalorimetric method at 37 °C The results showed that all of the organic compounds had the capacity to inhibit the growth of S. aureus in different extent. And the extent and duration of the inhibitory effect on the growth of S. aureus, judged from the rate constant (k), varied with the different structure of the Schiff base compounds. According to the power-time curves, the multiplication rate constant and inhibition ratio were calculated. The growth rate constant of S. aureus (in log phase) in the presence of Schiff base compounds decreased with the increasing of the concentrations of these compounds regularly. The experimental results revealed that the hydrophilicity of Schiff bases had a great influence on their antibacterial activity. Of these Schiff bases, the greater their hydrophilicity, the higher their antibacterial activity. The antibacterial structure-activity relationship (SAR) of Schiff base derivatives was also briefly discussed.     

Terpenoids from a Chinese Gorgonian Anthogorgia sp. and Their Antifouling Activities

Chemical examination of a Chinese gorgonian Anthogorgia sp. resulted in the isolation of seven terpenoids, including two new compounds, an rearranged serrulatane‐type diterpenoid anthogorgiene P ( 1 ) and a guaiazuene‐based terpenoid anthogorgiene Q ( 2 ). Anthogorgiene P ( 1 ) contains an unprecedented cubebane nucleus which is rarely found from nature. The structures of new compounds were elucidated on the basis of extensive spectroscopic methods (IR, UV, MS, CD and NMR). Compound 7 showed potent antifouling activity against the larval settlement of Balanus amphitrite, while 1 and 4 possessed moderate inhibition.     

Solvent-free one-pot synthesis,characterization, antibacterial and antifungal activities of novel spiropiperidinyl-1,2,4-triazolidine-3-thiones

A novel approach towards the synthesis of spiropiperidinyl 1,2,4-triazolidine-3-thiones was proposed, exploiting microwave activation coupled with solvent-free reaction conditions. In search for new leads towards potent antimicrobial agents, we tested all the synthesized compounds for their in vitro antibacterial activity against Bacillus subtilis and Micrococcus luteus and antifungal activity against Aspergillus niger, Candida albicans, Candida-6, and Candida-51. Two of the compounds exerted strong in vitro antibacterial activity against B. subtilis and M. luteus, and all the synthesized compounds were potent against the tested fungal strains.     

Minor compounds of the high purity salvianolic acid B freeze-dried powder from Salvia miltiorrhiza and antibacterial activity assessment

The study explored the isolation and characterisation of three compounds of high purity salvianolic acid B freeze-dried powder extracted from Salvia miltiorrhiza Bunge. A new salvianolic acid, salvianolic acid V (2) together with two known compounds (3–4) was identified. The antibacterial activity tests showed that compound 2 combined with clinical antibiotics such as Levofloxacin or Colistin sulphate together exhibited potent effects against MRSA or Acinetobacter baumanii. This report has considerably extended our knowledge about the diversity and bioactivity of caffeic acid derivatives from S. miltiorrhiza.     

A study on synthesis and antimicrobial activity of 4-acyl-pyrazoles

4-Acyl-pyrazole-3-carboxylic acids (1) were synthesized via the reaction of 4-acyl-2,3-furandiones (F) with hydrazone (1-benzylidene-2-(2,5-dimethyl-phenyl)-hydrazine) by heating under solid phase and their acid chlorides (2) were obtained. Then these derivatives were easily converted into the corresponding derivatives such as ester, amide, ureide, pyrazolo-pyridazine, etc. Totally 62 new compounds were synthesized. The structures of these new synthesized compounds were determined by spectroscopic methods and the in vitro antibacterial activity of newly synthesized compounds were carried out against some gram-positive and gram-negative bacteria by well diffusion method (zone inhibition). Our results have showed that these new synthesized compounds have much potent of antibacterial activity owing to containing of pyrazole and/or pyridazine, chromone, oxazine, furane, and pyrrole rings. Some of the new pyrazole derivatives exhibited higher activities than reference drugs against the representative bacteria.     

Antimicrobial flavonoids isolated from Indian medicinal plant Scutellaria oblonga inhibit biofilms formed by common food pathogens

Scutellaria oblonga Benth., a hitherto phytochemically unexplored Indian medicinal folklore plant was extracted with acetone and subjected to chromatography to yield nine flavonoids, for the first time from this plant. Antimicrobial assays were performed against 11 foodborne pathogens, and three molecules (Techtochrysin, Negletein and Quercitin-3-glucoside) depicted significant activity. These molecules were assessed for their rate of antibacterial action using time–kill curves which depicted complete inhibition of most of the bacteria within 12–16 h. The significant biofilm-reducing capability exhibited by these three molecules formed a significant finding of the current study. In most of the experiments, a 90–95% reduction in biofilms was observed. Thus, flavonoids as natural molecules from S. oblonga could be further researched to be used as potent antimicrobial and antibiofilm agents.     

Isolation, structure, and antibacterial activity of philipimycin, a thiazolyl peptide discovered from Actinoplanes philippinensis MA7347

Bacterial resistance to antibiotics, particularly to multiple drug resistant antibiotics, is becoming cause for significant concern. The only really viable course of action is to discover new antibiotics with novel mode of actions. Thiazolyl peptides are a class of natural products that are architecturally complex potent antibiotics but generally suffer from poor solubility and pharmaceutical properties. To discover new thiazolyl peptides potentially with better desired properties, we designed a highly specific assay with a pair of thiazomycin sensitive and resistant strains of Staphylococcus aureus, which led to the discovery of philipimycin, a new thiazolyl peptide glycoside. It was isolated along with an acid-catalyzed degradation product by bioassay-guided fractionation. Structure of both compounds was elucidated by extensive application of 2D NMR, 1D TOCSY, and HRESIFT-MS/MS. Both compounds showed strong antibacterial activities against gram-positive bacteria including MRSA and exhibited MIC values ranging from 0.015 to 1 microg/mL. Philipimycin was significantly more potent than the degradation product. Both compounds showed selective inhibition of protein synthesis, indicating that they targeted the ribosome. Philipimycin was effective in vivo in a mouse model of S. aureus infection exhibiting an ED50 value of 8.4 mg/kg. The docking studies of philipimycin suggested that a part of the molecule interacts with the ribosome and another part with Pro23, Pro22, and Pro26 of L11 protein, which helped in explaining the differential of activities between the sensitive and resistant strains. The design and execution of the bioassay, the isolation, structure, in vitro and in vivo antibacterial activity, and docking studies of philipimycin and its degradation product are described.     

Study on the synthesis and antimicrobial activity of novel cationic porphyrins

A novel series of quaternary ammonium cationic derivatives based on tetrapyridyl-porphyrin was synthesized.All the compounds were evaluated for their in vitro antibacterial activities against S.aureus,E.coli and P.aeruginosa,and antifungal activities against C.albicans,where microorganisms were exposed and unexposed to the irradiation.The results revealed that some of these compounds,especially,3a and 4a displayed satisfactory antibacterial activity against Gram-positive bacteria S.aureus and moderate an...