Biofilm inhibiting properties of compounds from the leaves of Warburgia ugandensis Sprague subsp ugandensis against Candida and staphylococcal biofilms.

ETHNOPHARMACOLOGICAL RELEVANCE: Warburgia ugandensis Sprague subspecies ugandensis is a plant widely distributed in Eastern, Central and Southern Africa. In humans, it is used to treat respiratory infections, tooth aches, malaria, skin infections, venereal diseases, diarrhea, fevers and aches. AIM OF THE STUDY: This study aims to identify the bioactive compounds against clinically important biofilm-forming strains of Candida and staphylococci that are responsible for tissue and implanted device-related infections. METHODS: Using a bioassay-guided fractionation approach, hexane -, ethanol -, acetone - and water extracts from the leaves of W. ugandensis, their subsequent fractions and isolated compounds were tested against both developing and preformed 24 h-biofilms of Candida albicans SC5314, Candida glabrata BG2, Candida glabrata ATCC 2001, Staphylococcus epidermidis 1457 and Staphylococcus aureus USA 300 using microtiter susceptibility tests. Planktonic cells were also tested in parallel for comparison purposes. Confocal scanning laser microscopy was also used to visualize effects of isolated compounds on biofilm formation. RESULTS: Warburganal, polygodial and alpha-linolenic acid (ALA) were the major bioactive compounds isolated from the acetone extract of W. ugandensis. For both warburganal and polygodial, the biofilm inhibitory concentration that inhibits 50% of C. albicans developing biofilms (BIC50) was 4.5 ±â€¯1 and 10.8 ±â€¯5 µg/mL respectively. Against S. aureus developing biofilms, this value was 37.9 ±â€¯8 µg/mL and 25 µg/mL with warburganal and ALA respectively. Eradication of preformed 24 h biofilms was also observed. Interestingly, synergy between the sesquiterpenoids and azoles against developing C. albicans biofilms resulted in an approximately ten-fold decrease of the effective concentration required to completely inhibit growth of the biofilms by individual compounds. The hydroxyl group in position C-9 in warburganal was identified as essential for activity against staphylococcal biofilms. We also identified additional promising bioactive sesquiterpenoids; drimenol and drimendiol from the structure-activity relationship (SAR) studies. CONCLUSIONS: ALA and four sesquiterpenoids: polygodial, warburganal, drimenol and drimendiol, have shown biofilm-inhibitory activity that has not been reported before and is worth following up. These compounds are potential drug candidates to manage biofilm-based infections, possibly in combination with azoles.

Synthesis of N-Acyl Sulfamates from Fluorosulfates and Amides.

A novel synthetic strategy toward  N-acyl sulfamates was developed. Interestingly, fluorosulfates, a new emerging class of electrophiles, were used to construct the sulfamate core. This precludes handling of chlorosulfonyl isocyanate and sulfamoyl chloride. In combination with amides, a wide and diverse set of N-acyl sulfamates was synthesized, including functionalized bioactive compounds. Furthermore, initial results showed that this method is also amenable to access N-thioacyl sulfamates.

Bioassay-guided isolation of active substances from Semen Torreyae identifies two new anthelmintic compounds with novel mechanism of action.

ETHNOPHARMACOLOGICAL RELEVANCE: Semen Torreyae, the seeds of Torreya grandis Fortune ex Lindley (Cephalotaxaceae) is a well-known traditional Chinese medicinal plant recorded in the Chinese Pharmacopeia (2010 version). It is widely used for treating intestinal parasites in China, owing to its desirable efficacy and safety. However, the anthelmintic compounds in Semen Torreyae have not yet been identified. AIM OF THE STUDY: This study aims to identify the compounds active against helminths from Semen Torreyae. In addition, we tested whether C. elegans strains resistant to currently-used anthelmintic drugs showed cross-resistance to these compounds. METHODS: A bioassay-guided isolation of anthelmintic compounds from Semen Torreyae was performed using a Caenorhabditis elegans (C. elegans) testing model. The structures of active compounds were elucidated by a combination of GC-MS, high resolution MS, and NMR. The median-effect method was employed to generate a combination index (CI) to evaluate the synergistic effect of the anthelmintic compounds. A panel of C. elegans mutant strains resistant against the major anthelmintic drug classes was used to study the cross-resistance to currently-used anthelmintic drugs. A panel of transient receptor potential (TRP) channel mutant strains was also tested to explore the possible mechanisms of action of the anthelmintic compounds. RESULTS: The bioassay-guided isolation led to two active compounds, i.e. galangal acetate (IC50: 58.5 ±â€¯8.9 µM) and miogadial (IC50: 25.1 ±â€¯5.4 µM). The combination of galangal acetate and miogadial resulted in a synergistic effect at IC50, IC70, and IC90 levels (CIs < 1). Galangal acetate and miogadial demonstrated similar activity against drug-resistant C. elegans strains compared to the wild-type strain. In addition, none of the TRP mutants was significantly resistant to galangal acetate or miogadial compared to wild type worms. CONCLUSIONS: We identified the bioactive compounds from Semen Torreyae responsible for its anthelmintic activity: galangal acetate and miogadial. The two anthelmintic compounds demonstrated a synergistic effect against C. elegans. Galangal acetate and miogadial are unlikely to act on the targets of currently-used anthelmintics (ivermectin, levamisole, benomyl and aldicarb), and an action on TRP channels appears to be ruled out as well. In summary, galangal acetate and miogadial are promising anthelmintic hits worth further investigation.

Direct Access to Aryl Bis(trifluoromethyl)carbinols from Aryl Bromides or Fluorosulfates: Palladium-Catalyzed Carbonylation.

A palladium-catalyzed carbonylative approach for the direct conversion of (hetero)aryl bromides into their α,α-bis(trifluoromethyl)carbinols is described, and it employs only stoichiometric amounts of carbon monoxide and trifluoromethyltrimethylsilane. In addition, aryl fluorosulfates proved highly compatible with these reaction conditions. The method is tolerant of a diverse set of functional groups, and it is adaptable to late-stage carbon-isotope labeling.

Active principles of Tetradenia riparia. IV. Anthelmintic activity of 8(14),15-sandaracopimaradiene-7α,18-diol.

ETHNOPHARMACOLOGICAL RELEVANCE: Tetradenia (T.) riparia (Hochst.) Codd (Lamiaceae), formerly known as Iboza riparia (Hochst.) N.E.Br., is one of the most frequently used medicinal plants in traditional Rwandese medicine. It was used as a remedy against a wide range of diseases including malaria, angina, yaws, dental abscesses, headache, worm infections and several kinds of fevers and aches. AIM OF THE STUDY: This study aims to identify the compounds active against helminths from Tetradenia riparia. METHODS: A bioassay-guided isolation of anthelmintic compounds from the leaves of Tetradenia riparia was performed using a Caenorhabditis elegans (C. elegans) testing model. RESULTS: The bioassay-guided isolation led to one active compound, i.e. 8(14),15-sandaracopimaradiene-7α,18-diol. Its IC50 value was 5.4 ± 0.9 µg/mL (17.8 ± 2.9 µM). CONCLUSIONS: We identified the bioactive compound from Tetradenia riparia responsible for its anthelmintic activity: 8(14),15-sandaracopimaradiene-7α,18-diol. Although the compound and several of its bioactivities have been described before, this is the first report of its anthelmintic effect.

Ex Situ Generation of Sulfuryl Fluoride for the Synthesis of Aryl Fluorosulfates.

A convenient transformation of phenols into the corresponding aryl fluorosulfates is presented: the first protocol to completely circumvent direct handling of gaseous sulfuryl fluoride (SO2F2). The proposed method employs 1,1'-sulfonyldiimidazole as a precursor to generate near-stoichiometric amounts of SO2F2 gas using a two-chamber reactor. With NMR studies, it was shown that this ex situ gas evolution is extremely rapid, and a variety of phenols and hydroxylated heteroarenes were fluorosulfated in good to excellent yields.

Carbonylation as a novel method for the assembly of pyrazine based oligoamide alpha-helix mimetics.

The design and synthesis of oligoamide α-helix peptidomimetics is reported. The oligoamide type systems are prepared in a modular fashion by coupling the monomers using palladium-catalyzed carbonylation chemistry. This enabled us to use substrates with a low nucleophilicity, leading to previously unreported pyrazine based oligoamide α-helix mimetics. The proof of principle is given by synthesizing a small set of compounds. Various end-capping groups were introduced and also a mixed multimer was successfully prepared.

Optimization of a Nile Red method for rapid lipid determination in autotrophic, marine microalgae is species dependent.

Several studies have been conducted to develop rapid methods for quantification of lipid content in microalgae, as an alternative for time consuming gravimetric methods. Different studies showed that lipid staining with Nile Red in whole cell suspensions and subsequently quantification by the use of a spectrofluorometric device is a promising method, but a profound optimization and validation is rare. It has already been proven that the correlation curve for quantification is species dependent, but it has not yet been investigated whether this is also the case for the optimization of the Nile Red assay protocol. Therefore, two autotrophic, marine microalgae, Nannochloropsis oculata and T-Isochrysis lutea, strongly differing in e.g. cell wall structure, were selected in this study to investigate whether optimization of the Nile Red assay is species dependent. Besides this, it was checked for one of these species, Nannochloropsis, whether the lipid content, determined by the Nile Red assay, could indeed be correlated with the neutral and/or total lipid content determined by gravimetric methods. It was found that optimization of the Nile Red assay was strongly species dependent. Consequently, optimization has to be done for each species before using the assay. For Nannochloropsis, a good correlation was found between total and neutral lipid content obtained by the Nile Red assay and by gravimetric methods.