Repurposing primaquine as a polyamine conjugate to become an antibiotic adjuvant

In our search for new antibiotic adjuvants as a novel strategy to deal with the emergence of multi-drug resistant (MDR) bacteria, a series of succinylprimaquine-polyamine (SPQ-PA) conjugates and derivatives of a cationic amphiphilic nature have been prepared. Evaluation of these primaquine conjugates for intrinsic antimicrobial properties and the ability to restore the antibiotic activity of doxycycline identified two derivatives, SPQ-PA3-8-3 and SPQ-PA3-10-3 that exhibited intrinsic activity against the Gram-positive bacteria Staphylococcus aureus and the yeast Cryptococcus neoformans. None of the analogues were active against the Gram-negative bacterium Pseudomonas aeruginosa. However, in the presence of a sub-therapeutic amount of doxycycline (4.5 µM), both SPQ-PA3-4-3 and SPQ-PA3-10-3 compounds displayed potent antibiotic adjuvant properties against P. aeruginosa, with MIC's of 6.25 µM. A series of derivatives were prepared to investigate the structure-activity relationship that explored the influence of both a simplified aryl lipophilic substituent and variation of the length of the polyamine scaffold on observed intrinsic antimicrobial properties and the ability to potentiate the action of doxycycline against P. aeruginosa.

An Acetylenic Lipid from the New Zealand Ascidian Pseudodistoma cereum: Exemplification of an Improved Workflow for Determination of Absolute Configuration of Long-Chain 2-Amino-3-alkanols

An acetylenic 2-amino-3-alcohol, distaminolyne B (2), isolated from the New Zealand ascidian Pseudodistoma cereum, is reported. The isolation and structure elucidation of 2 and assignment of 2S,3S absolute configuration (AC) using the exciton coupled circular dichroism technique are described. Using a methodologically facile workflow, the same AC was also established by analysis of specific rotation, terminal methyl C-1 δ_C chemical shift, and NH δ_H and J values of the N,O-diacetate derivative.

The Configuration of Distaminolyne A is S: Quantitative Evaluation of Exciton Coupling Circular Dichroism of N, O- Bis-arenoyl-1-amino-2-alkanols

The 2 S configuration of the marine natural product distaminolyne A was recently disputed based upon total synthesis, yet paradoxically supported by a second independent total synthesis from a different research group. We now verify the 2 S configuration of distaminolyne A by extensive chiroptical studies and support the veracity of the EC ECD method originally used to prove it. The origin of the apparent paradox appears to lie in the limits of precision of polarimetry in the context of weakly rotatory molecules, which strikes a cautionary note on the reliability of "reassignment" of natural product configurations based solely on specific rotation.

Enantiomeric Variability of Distaminolyne A. Refinement of ECD and NMR Methods for Determining Optical Purity of 1-Amino-2-Alkanols

Sample configurations of distaminolyne A (1a); isolated from the ascidians Pseudodistoma opacum and P. cereum, and collected at different sites in New Zealand, were investigated by two methods: Exciton coupled electronic circular dichroism (EC ECD) of the corresponding N,O-dibenzoyl derivative 1b; and chiral reagent derivatization of 1a with (S)- and (R)-α-methoxyphenylacetic acid (MPA), followed by ¹H-NMR analysis. Configuration and optical purity of 1a (%ee) was found to vary depending on the geographic distribution of ascidian colonies. An improved method for preparing N,O-diarenoyl derivatives of 1a was optimized. The EC ECD method was found to be complementary to the MPA-NMR method at different ranges of %ee.

Total Synthesis of (-)-Bicubebin A, B, (+)-Bicubebin C and Structural Reassignment of (-)-cis-Cubebin

The first total synthesis of (-)-bicubebin A, and two previously unreported dilignans, (-)-bicubebin B and (+)-bicubebin C has been achieved through the dimerization of (-)-cubebin, confirming the structure and absolute stereochemistry of (-)-bicubebin A. Analysis of the data for (-)-bicubebin B showed it matched that of reported compound (-)-cis-cubebin. The NMR data of the subsequently synthesized proposed structure of cis-cubebin confirmed that its original proposed structure was incorrect.

Biologically Active Acetylenic Amino Alcohol and N-Hydroxylated 1,2,3,4-Tetrahydro-β-carboline Constituents of the New Zealand Ascidian Pseudodistoma opacum

The first occurrence of an acetylenic 1-amino-2-alcohol, distaminolyne A (1), isolated from the New Zealand ascidian Pseudodistoma opacum, is reported. The isolation and structure elucidation of 1 and assignment of absolute configuration using the exciton coupled circular dichroism technique are described. In addition, a new N-9 hydroxy analogue (2) of the known P. opacum metabolite 7-bromohomotrypargine is also reported. Antimicrobial screening identified modest activity of 1 toward Escherichia coli, Staphylococcus aureus, and Mycobacterim tuberculosis, while 2 exhibited a moderate antimalarial activity (IC50 3.82 μM) toward a chloroquine-resistant strain (FcB1) of Plasmodium falciparum.

Discovery and evaluation of thiazinoquinones as anti-protozoal agents

Pure compound screening has identified the dioxothiazino-quinoline-quinone ascidian metabolite ascidiathiazone A (2) to be a moderate growth inhibitor of Trypanosoma brucei rhodesiense (IC₅₀ 3.1 μM) and Plasmodium falciparum (K1 dual drug resistant strain) (IC₅₀ 3.3 μM) while exhibiting low levels of cytotoxicity (L6, IC₅₀ 167 μM). A series of C-7 amide and Δ²⁽³⁾ analogues were prepared that explored the influence of lipophilicity and oxidation state on observed anti-protozoal activity and selectivity. Little variation in anti-malarial potency was observed (IC₅₀ 0.62–6.5 μM), and no correlation was apparent between anti-malarial and anti-T. brucei activity. Phenethylamide 7e and Δ²⁽³⁾-glycine analogue 8k exhibited similar anti-Pf activity to 2 but with slightly enhanced selectivity (SI 72 and 93, respectively), while Δ²⁽³⁾-phenethylamide 8e (IC₅₀ 0.67 μM, SI 78) exhibited improved potency and selectivity towards T. brucei rhodesiense compared to the natural product hit. A second series of analogues were prepared that replaced the quinoline ring of 2 with benzofuran or benzothiophene moieties. While esters 10a/10b and 15 were once again found to exhibit cytotoxicity, carboxylic acid analogues exhibited potent anti-Pf activity (IC₅₀ 0.34–0.035 μM) combined with excellent selectivity (SI 560–4000). In vivo evaluation of a furan carboxylic acid analogue against P. berghei was undertaken, demonstrating 85.7% and 47% reductions in parasitaemia with ip or oral dosing respectively.

Investigation of the electrophilic reactivity of the cytotoxic marine alkaloid discorhabdin B

The mechanisms of action of the cytotoxic marine pyrroloiminoquinone alkaloids the discorhabdins are unknown. We have determined that discorhabdin B acts as an electrophile towards biomimetic thiol nucleophiles leading to debrominated adducts. In contrast, less potent cytotoxins discorhabdins D and Q failed to react, supporting an SAR model of cytotoxicity requiring an orchestrated combination of an electrophilic Δ(1) carbon centre and a nucleophilic N-18 amine for potent activity. The stereospecific nature of nucleophile trapping exhibited by both enantiomers of discorhabdin B implies the biogenesis of ovothiol A substituted discorhabdins H, H(2), K and K(2) need not be mediated by enzymatic processes.

Anti-inflammatory and antimalarial meroterpenoids from the New Zealand ascidian Aplidium scabellum

Bioassay-directed fractionation of an extract of the New Zealand ascidian Aplidium scabellum has afforded the anti-inflammatory secondary metabolite 2-geranyl-6-methoxy-1,4-hydroquinone-4-sulfate (1) and a family of pseudodimeric meroterpenoids scabellones A (2)-D (5). The benzo[c]chromene-7,10-dione scaffold contained within scabellones A-D is particularly rare among natural products. The structures were elucidated by interpretation of NMR data. Scabellone B was also identified as a moderately potent, nontoxic inhibitor of Plasmodium falciparum.

Antimalarial β-carbolines from the New Zealand ascidian Pseudodistoma opacum

One tetrahydro-β-carboline, (-)-7-bromohomotrypargine (1), and three alkylguanidine-substituted β-carbolines, opacalines A, B, and C (2-4), have been isolated from the New Zealand ascidian Pseudodistoma opacum. The structures of the metabolites were determined by analysis of mass spectrometric and 2D NMR spectroscopic data. Natural products 2 and 3, synthetic debromo analogues 8 and 9, and intermediate 16 exhibited moderate antimalarial activity toward a chloroquine-resistant strain of Plasmodium falciparum, with an IC50 range of 2.5-14 μM. The biosynthesis of 1-4 is proposed to proceed via a Pictet-Spengler condensation of 6-bromotryptamine and the α-keto acid transamination product of either arginine or homoarginine. Cell separation and 1H NMR analysis of P. opacum identified tetrahydro-β-carboline 1 to be principally located in the zooids, while fully aromatized analogues 2-4 were localized to the test.

Didemnidines A and B, indole spermidine alkaloids from the New Zealand ascidian Didemnum sp

Two new indole spermidine alkaloids, didemnidines A (1) and B (2), have been isolated from the New Zealand ascidian Didemnum sp. The structures of the metabolites, determined by analysis of 2D NMR spectra and confirmed via synthesis, embody an indole-3-glyoxylamide moiety linked to the N(1) position of spermidine, the latter motif being particularly rare among marine natural products. Didemnidine B and a synthetic precursor exhibited mild in vitro growth inhibition of Plasmodium falciparum with IC(50)'s of 15 and 8.4 μM, respectively.

Isolation and characterization of diastereomers of discorhabdins H and K and assignment of absolute configuration to discorhabdins D, N, Q, S, T, and U

Investigations of four different sponge populations of Latrunculia species collected in New Zealand waters has led to the characterization of a new diastereomer of discorhabdin H, named discorhabdin H2, confirmation of the structure of discorhabdin K ((+)-7), and presentation of a new diastereomer, discorhabdin K2 ((-)-8). In each case the structures were established by extensive NMR and MS studies and the absolute configurations interrogated by electronic circular dichroism (ECD). Absolute configurations were assigned to the known metabolites discorhabdins H, D, 2-hydroxy-D, N, and Q by comparison of ECD spectra with those recorded for discorhabdin alkaloids of defined absolute configuration, while the configurations of discorhabdins S, T, and U were assigned by semisynthesis from (+)-(6S,8S)-discorhabdin B.

Anti-inflammatory thiazine alkaloids isolated from the New Zealand ascidian Aplidium sp.: inhibitors of the neutrophil respiratory burst in a model of gouty arthritis

Ascidiathiazones A (3) and B (4), two new tricyclic thiazine-containing quinolinequinone alkaloids, were isolated from the New Zealand ascidian Aplidium species. Both compounds inhibited the in vitro production of superoxide by PMA-stimulated human neutrophils in a dose-dependent manner with IC50 1.55 +/- 0.32 and 0.44 +/- 0.09 microM, respectively. In vivo inhibition of superoxide production by peritoneal neutrophils in a murine model of gout was observed for both compounds with oral doses of 25.6 micromol/kg. Ascidiathiazone A (3) was synthesized in four steps from 8-hydroxyquinoline-2-carboxylic acid.

E/Z-rubrolide O, an anti-inflammatory halogenated furanone from the New Zealand ascidian Synoicum n. sp

Bioassay-directed fractionation of extracts of a Synoicum n. sp. ascidian from New Zealand led to the isolation of the principal anti-inflammatory component, which was identified by spectroscopic methods as a new member of the rubrolide family, rubrolide O (1), existing as a mixture of E/Z isomers.

Natural product growth inhibitors of Mycobacterium tuberculosis

This review covers natural products (secondary metabolites) with reported growth inhibitory activity towards Mycobacterium tuberculosis or related organisms. Such compounds have been isolated from a variety of sources including terrestrial and marine plants and animals, and microorganisms, with the express intent of identifying novel scaffolds for the development of new antituberculosis agents. The literature from January 2003 to December 2005 (inclusive) is reviewed and 146 references to 353 compounds are cited. The compounds are presented in order of chemical type, namely lipids/fatty acids and simple aromatics, phenolics and quinones, peptides, alkaloids, terpenes (monoterpenoids, diterpenes, sesquiterpenes and triterpenes), steroids and miscellaneous structures.

N2,N2,7-trimethylguanine, a new trimethylated guanine natural product from the New Zealand ascidian, Lissoclinum notti

From the New Zealand ascidian, Lissoclinum notti a new natural product, N2,N2,7-trimethylguanine (1) has been isolated. The structure of 1 was elucidated by analysis of spectroscopic data.

Comb wax effects on the ontogeny of honey bee nestmate recognition

We addressed the general question of how kin recognition cues develop by investigating cue differentiation between colonies of the honey bee, Apis mellifera. In honey bee colonies, exposure to the wax comb is a critical component of the development of kin recognition cues. In this study, we determined how the cues develop under natural conditions (in swarms), whether the genetic source and age of the wax affect cue ontogeny, and whether exposure to wax, as in normal development, affects preferential feeding among bees within social groups. Cue development in swarms coincided with wax production, rather than with the presence of brood or the emergence of new workers; this finding supported previous observations concerning the importance of wax in cue ontogeny. Effective cue development required a match between the genetic source of the workers attempting to enter the hive, the wax to which they were exposed, and the guards at the hive entrance. The wax must also have been exposed to the hive environment for some time. Cues gained from wax did not mask or override cues used in preferential feeding interactions; this finding supports the contention that two recognition systems, one for nestmate recognition and the other for intra-colonial recognition, are present. The results fit a general model for cue development in nestmate recognition that relies on the use of nesting materials as an intermediary; the evolutionary significance of this model is discussed. Copyright 1998 The Association for the Study of Animal Behaviour.

Tongue reconstruction procedures for treatment of cancer

Cancer of the tongue is the second most common oral cavity malignancy seen in the general population. When otolaryngologists decide to treat patients surgically, perioperative nurses must institute special nursing interventions directed toward patients' tongue reconstruction procedures and rehabilitation. Surgical management of patients undergoing tongue reconstruction procedures requires extensive knowledge of the tongue's anatomy and both current and new physiology created by surgical reconstructive procedures. Equally important is the multidisciplinary care provided to patients during rehabilitation.

Contact with a sow in oestrus or a mature boar stimulates the onset of oestrus in weaned sows

Post weaning anoestrus can represent a significant source of reproductive inefficiency in pig production. Although many factors such as breed, parity, season and nutrition are known to influence the interval between weaning and remating, the effect of the sow's social environment after weaning is largely unknown. For this experiment six groups of Large White/Landrace cross-bred sows weaned between August 1989 and March 1990 at a mean of 29 days after farrowing were used to investigate the effect of social environment on the onset of oestrus after weaning in the sow. Groups two, three or four sows were exposed in six replicates to the following four treatments: (1) 18 were isolated as controls, (2) 16 were housed next to an anoestrous ovariectomised sow and allowed 10 minutes physical contact with it daily, (3) 15 were housed next to an ovariectomised sow, induced into oestrus by the injection of 1 mg oestradiol benzoate, and allowed 10 minutes physical contact with it daily, and (4) 16 were housed next to a mature boar and allowed 10 minutes physical contact with it daily. Significantly more sows in treatments 3 and 4 showed oestrus within 10 days of weaning (P less than 0.05), and the onset of oestrus was more synchronised in the sows in treatment 3 than in any other treatment (P less than 0.001). The exposure of the weaned sows to an oestrous sow or a boar overcame the extension of the weaning to remating interval which occurred over the summer and in primiparous animals in other treatments.