Antibacterial properties of zeylasterone, a triterpenoid isolated from Maytenus blepharodes, against Staphylococcus aureus.

The anti-staphylococcal properties of zeylasterone and demethylzeylasterone, two 6-oxophenolic triterpenoids isolated from Maytenus blepharodes, were investigated. Zeylasterone was more active than demethylzeylasterone on Staphylococcus aureus cells, showing bactericidal activity at 30 µg/ml (6 × MIC) in less than three hours and bacteriostatic at lower concentrations. At the same cell density, a more drastic reduction in CFU count was obtained when the triterpenoid was incorporated into cultures growing actively. Zeylasterone at 3 × MIC added on S. aureus cultures showed an early inhibitory effect on incorporation of radiolabeled thymidine, uridina and N-acetyl-glucosamine, and later on leucine. It also caused cell membrane disruption in S. aureus, as shown by the inhibition of radiolabeled precursor uptake, rapid potassium leakage, inhibition of NADH oxidation, and formation of mesosome-like structures around the septa. The structural features of the molecule, the blockage of solute transport through the membrane and changes in its permeability, suggest that zeylasterone acts mainly on cytoplasmic membrane.

Activity and mechanism of the action of zeylasterone against Bacillus subtilis.

AIMS: To investigate the antimicrobial properties of 6-oxophenolic triterpenoids isolated from Maytenus blepharodes against different micro-organisms and the mode of action on Bacillus subtilis. METHODS AND RESULTS: The activity of zeylasterone and demethylzeylasterone was evaluated by microdilution method. Zeylasterone showed a higher activity, being active against Gram-positive bacteria (minimum inhibitory concentration 3-20 microg ml(-1)) and Candida albicans (10 microg ml(-1)). Killing curves revealed a bacteriostatic effect on B. subtilis that was dependent on the growth phase and inoculum size. Zeylasterone caused cell membrane alterations in B. subtilis, as shown by potassium leakage and formation of mesosome-like structures. However, membrane disruption was not revealed by either LIVE/DEAD Baclight assay or measurement of intracellular constituent efflux. Zeylasterone showed an early effect on N-acetyl-glucosamine and uridine incorporation and later on that of thymidine and leucine. CONCLUSIONS: Diverse micro-organisms exhibit sensitivities towards compounds studied. The permeability changes in the cytoplasmic membrane and nonsimultaneous ceasing of macromolecular synthesis suggest that zeylasterone could act on multiple targets on B. subtilis. SIGNIFICANCE AND IMPACT OF THE STUDY: The activity showed against B. subtilis as a model of spore-forming bacteria would provide valuable information for further studies in the development of 6-oxophenolic triterpenoids as antiseptic and disinfectant properties.

Efficacy of ciprofloxacin implants in treating experimental osteomyelitis.

Ciprofloxacin (CFX) implants containing poly(D,L-lactide) and calcium phosphates (tricalcium phosphate and hydroxyapatite) was evaluated in 50 rabbits in an experimental osteomyelitis model. Their femoral cavity was inoculated with Staphylococcus aureus. After 2 weeks, the infected focus was cleaned out and the delivery system implanted. The infection and subsequent response to treatment were evaluated by microbiological analysis, biochemical and hematological markers, body weight, temperature, clinical signs, X-rays, and histology. Infected bone cultures, treated with CFX implants, showed reduced bacterial growth against controls. All CFX was released within 6 weeks. All animals recovered within 4 weeks. Even 12 weeks after implantation, no recurrence of infection was observed. Serum C-reactive protein, platelet, and leukocyte levels increased in all animals before treatment, and 4 weeks after it were maintained or rose in control animals, while decreased to normal levels in treated ones. Body weight was characterized by pretreatment losses, then gains during recuperation, or further loss in untreated animals; with no significant intraindividual differences in body temperature. Body weight, leucocytes, platelets, and C-reactive protein turned out to be highly useful markers for monitoring this kind of infection and its treatment. CFX implants demonstrated to be an effective therapy for S. aureus bone infection. Their efficacy was also reflected in decreasing severity of clinical signs, nonprogress of radiological signs indicative of infection, and good integration into bone structure. Histological examination revealed repair, with new bone formation extending into implants.

Triterpene trimers from Maytenus scutioides: cycloaddition compounds?

Two novel trimers, triscutins A and B (1 and 2), based on pristimerin triterpene units, were isolated and characterized from Maytenus scutioides. Their structures were determined on the basis of spectroscopic evidence, including 1H-13C heteronuclear correlation (HMQC), long-range correlation with inverse detection (HMBC), and ROESY NMR experiments; and their absolute configurations, by means of CD studies. Compounds 1 and 2 were assayed for antimicrobial and cytotoxic activities, and their possible biosynthetic route is proposed.

A new bioactive norquinone-methide triterpene from Maytenus scutioides.

By antimicrobial and cytotoxic-guided fractionation, a bioactive norquinone-methide triterpene, 15 alpha-hydroxypristimerin, was isolated from a South American medicinal plant, Maytenus scutioides. Its structure was determined on the basis of spectroscopic evidence. Successful chemical transformation of pristimerin to netzahualcoyene indicates that the 15-hydroxy compounds seems to be a possible percursor of 14(15)-ene-quinone-methide-triterpenoids in the biogenetic pathway.

Biological activities of some Argyranthemum species.

Seven species of the genus Argyranthemum were studied for antimicrobial and cytotoxic activities. Argyranthemum adauctum, A. foeniculaceum and A. frutescens showed antimicrobial activity against Gram-positive and Gram-negative and cytotoxic activity against HeLa and Hep-2 cell lines. Two new acetylenic compounds, frutescinol isovalerate and 3'-demethyl frutescinol isovalerate, were isolated from A. frutescens and their structures elucidated by spectroscopic studies.

Antibiotic phenol nor-triterpenes from Maytenus canariensis.

The new phenols 6-oxo-tingenol, 3-O-methyl-6-oxo-tingenol and 6-oxo-iguesterol were isolated from the root bark of Maytenus canariensis. Their structures were determined by 1H and 13C NMR spectroscopic studies, including HMQC, HMBC, DEPT and ROESY and chemical transformations. The synthesis of 6-oxo-tingenol was achieved from tingenone. These compounds exhibit antibiotic activity against Gram-positive bacteria.

Scutione, a new bioactive norquinonemethide triterpene from Maytenus scutioides (Celastraceae).

Scutione (1), a new norquinonemethide triterpene with a netzahualcoyene type skeleton, has been isolated from the root bark of Maytenus scutioides (Celastraceae) by bioactivity-directed fractionation. The structure of 1 has been elucidated by means of 1H and 13C NMR spectroscopic studies, including 1H-13C heteronuclear correlation (HETCOR), a long-range correlation spectrum with inverse detection (HMBC) and ROESY experiments. Compound 1 showed antibiotic activity against Gram-positive bacteria and modest cytotoxic activity against HeLa, Hep-2 and Vero cell lines. Fluoride derivatives 2-4 were prepared and assayed for bioactivity, where 2 showed slight improvement of the cytotoxic potency.

Xanthine oxidase inhibitory activity of some Panamanian plants from Celastraceae and Lamiaceae.

Thirty four crude extracts of Panamanian plants, from nine species of Celastraceae and Lamiaceae, were assayed for xanthine oxidase (XO) inhibitory activity. The enzymatic activity was estimated by measuring the increase in absorbance at 290 nm due to uric acid formation. Eighty five percent of the crude extracts were found to possess XO inhibitory activity at 50 micrograms/ml and all the extracts of the species from Lamiaceae were active even at 1 micrograms/ml. The ethanol extracts of Hyptis obtusiflora Presl ex Benth. (Lamiaceae) and H. lantanaefolia Poit. (Lamiaceae) exhibited the highest activity with an inhibition of approximately 40% at 1 micrograms/ml.

Biological activity of secondary metabolites from Bupleurum salicifolium (Umbelliferae).

Secondary metabolites from Bupleurum salicifolium were tested against viruses, Gram-positive and Gram-negative bacteria, the yeast Candida albicans, the nematodes Globodera pallida and G. rostochiensis, the insect Spodoptera littoralis and the crustacean Artemia salina. These compounds were also tested against tumoral and non-tumoral cell lines. The polyacetylene 8S-heptadeca-2(Z)-9(Z)-diene-4,6-diyne-1,8-diol exhibited toxicity for A. salina and specific antibiotic activity against Gram-positive bacteria. Nine of the lignans and one coumarin showed toxicity for A. salina, and the lignans bursehernin and matairesinol inhibited the hatching of the two nematode species. These are the first lignans that have been reported as affecting phytoparasitic nematodes, and the first natural products known to have an effect on the hatching of G. pallida. Lignans may play a role in the defence mechanisms of potato plants, as allelopathic substances acting against cyst-forming nematodes.

Antibiotic activity and absolute configuation of 8S-heptadeca-2(Z),9(Z)-diene-4,6-diyne-1,8-diol from Bupleurum salicifolium.

A polyacetylene has been isolated from Bupleurum salicifolium. Its structure and absolute configuration were determined to be 8S-heptadeca-2(Z),9(Z)-diene-4,6-diyne-1,8-diol [1] by means of 1H- and 13C-nmr spectroscopic studies, including 1H-13C heteronuclear correlation (HMQC) and long-range correlation spectra with inverse detection (HMBC). Its absolute configuration was determined by application of the Horeau method. This compound exhibited significant antibiotic activity against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis. Also isolated during this investigation were the known compounds; betulin, herniarin, 6,7,8-trimethoxycoumarin, p-hydroxyphenethyl alcohol, pluviatolide, guamaroline, bursehernin, guayadequiol, kaerophyllin, and matairesinol dimethyl ether.

Screening of antimicrobial and cytotoxic activities of Panamanian plants.

34 crude extracts of Panamanian plants, representing 4 species of Celastraceae and 5 species of Lamiaceae, have been screened for antimicrobial activity against thirteen bacterial strains and two yeasts. The cytotoxic activity was assayed against HeLa and Hep-2 cell lines. Fifty-three percent were found to have significant antimicrobial activity against at least two of the organisms tested, and 26.5 percent showed an IC(50) < 100 µg/ml against one cell line.

Isolation of an Enterobacter agglomerans strain with inhibitory activity on Pseudomonas aeruginosa.

Antagonism between Enterobacter agglomerans and Pseudomonas aeruginosa was due to an extracellular substance produced by E. agglomerans which accumulates in the culture medium. This substance was also toxic to Escherichia coli and Staphylococcus albus and its MIC for P. aeruginosa ranged between 7.8 and 3.9 micrograms/ml. However, when the extracts from the culture medium were irradiated from 2 h with white light (15 mW/cm2), the MIC was lower (3.9-1.9 micrograms/ml) suggesting that the active substance was a phototoxin.

Mode of action of netzahualcoyone.

The activity of netzahualcoyone on Bacillus subtilis and Escherichia coli was studied. The product inhibited the respiration of intact cells of B. subtilis but had no effect on the respiration of E. coli. However, when preparations of sonically disrupted cells were examined, inhibitory activity on both bacteria was observed.

Synthesis of some derivatives of 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(piperazin-1-yl)-3-quino linecarbo xylic acid (norfloxacin) as potential antibacterial agents.

Twelve new fluoroquinolones, structurally related to norfloxacin, have been synthesized in order to investigate the effect of substituents at the secondary nitrogen of the piperazine ring on antimicrobial activity. The new substances (carbamates, isoureas, guanidines, ureas and cyanamides) tested on a variety of gram-positive and gram-negative organisms showed lower activity than the model compound.