Michael C. Bowyer

Anhydride modified cantharidin analogues: synthesis, inhibition of protein phosphatases 1 and 2A and anticancer activity

Two series of anhydride modified cantharidin analogues were synthesised and screened for their phosphatase inhibition (PP1 and PP2A) and cytotoxicity in various cancer cell lines (Ovarian A2780, ADDP; Osteosarcoma 143B; and Colon HCT116 and HT29). One series was synthesised by a novel, high yielding one-pot hydrogenation-ring-opening-esterification procedure, the other by acid catalysed acetal formation. Analogues 5-7 and 9 displayed moderate PP2A selectivity (ca. 5- to 20-fold) and inhibition typically in the low microM range (comparable, in some cases to cantharidin). The anticancer activity of these analogues varied with the cell line under study; however, many of them showed selective cytotoxicity for the colon tumour cell lines.

Cantharidin analogues: synthesis and evaluation of growth inhibition in a panel of selected tumour cell lines

Diels-Alder addition of furans (furan, furfuryl alcohol, and 3-bromofuran) to maelic anhydride yields three distinct 5,6-dehydronorcantharidins. Hydrogenation of (4,10-dioxatricyclo[5.2.1.0]decane-3,5-dione) (4a), in dry ethanol affords the monoester (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic aid monoethyl ester) (6). Subsequent transesterification affords a series of monoesters (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid monomethyl ester (7)), 7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid monopropyl ester (8), (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid monohexyl ester (9)) and differentially substituted diesters (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid 2-ethyl ester 3-isopropyl ester) (10), and (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic acid 2-ethyl ester 3-phenyl ester) (11). Analogues were firstly screened for their ability to inhibit protein phosphatases 1 (PP1) and 2A (PP2A) as the lead compounds cantharidin (1) and norcantharidin (2) are known PP1 and PP2A inhibitors. Only analogues 4a, 6-8 displayed good PP1 and PP2A inhibition (PP1 IC(50)s=2.0, 2.96, 4.71, and 4.82 microM, respectively; PP2A IC(50)s=0.2, 0.45, 0.41, and 0.47 microM, respectively). All analogues were also screened for their anti-cancer potential against a panel of tumour cell lines, HL60, L1210, SW480, WiDr, HT29, HCT116, A2780, ADDP, and 143B, producing GI(50) values ranging from 6 microM to >1000 microM. Analogues possessing good PP1 and/or PP2A inhibition also returned moderate to good anti-cancer activity. Analogues with substituents directly attached to the intact bicyclo[2.2.1]heptane skeleton were poor to moderate anti-cancer agents. This correlates well with their lack of PP1 or PP2A activity. Analogues capable of undergoing a facile ring opening of the anhydride or with a single carboxylate were good PP1 and PP2A inhibitors, largely correlating to the observed anti-cancer activity in all cases, except 11. Analogue 11, whist neither a PP1 nor a PP2A inhibitor shows anti-cancer activity comparable to 1 and 2. We believe that intracellular esterases generate the corresponding dicarboxylate, which is a potent PP1 and PP2A inhibitor, and that it is this species which is responsible for the observed anti-cancer activity.

Molecularly imprinted polymers (MIPs): sensing, an explosive new opportunity?

Our group is currently developing in-field detection systems alongside the Australian Federal Police Forensic Services utilising molecularly imprinted polymers as the recognition elements. This review looks at MIP synthesis and our perceptions of future directions from an Australian and forensic perspective.

L-Theanine: properties, synthesis and isolation from tea

Theanine is a non-protein amino acid that occurs naturally in the tea plant (Camellia sinensis) and contributes to the favourable taste of tea. It is also associated with effects such as the enhancement of relaxation and the improvement of concentration and learning ability. It is also linked with health benefits including the prevention of certain cancers and cardiovascular disease, the promotion of weight loss and enhanced performance of the immune system. Thus, there has been a significant rise in the demand for theanine. While theanine has been chemically and biologically synthesised, techniques to isolate theanine from natural sources remain an important area of research. In this review article, the properties and health benefits of theanine are summarised and the synthesis and isolation of theanine are reviewed and discussed. Future perspectives for the isolation of theanine from natural sources are also outlined.

Cantharimides: A New Class of Modified Cantharidin Analogues Inhibiting Protein Phosphatases 1 and 2A

Cantharidin and its analogues have been of considerable interest as potent inhibitors of the serine/threonine protein phosphatases 1 and 2A (PP1 and PP2A). However, limited modifications to the parent compounds is tolerated. As part of an on-going study we have developed a new series of cantharidin analogues, the cantharimides. Inhibition studies indicate that cantharimides possessing a D- or L-histidine, are more potent inhibitors of PP1 and PP2A (PP1 IC(50)=3.22+/-0.7 microM; PP2A IC(50)=0.81+/-0.1 microM and PP1 IC(50)=2.82+/-0.6 microM; PP2A IC(50)=1.35+/-0.3 microM, respectively) than norcantharidin (PP1 IC(50)=5.31+/-0.76 microM; PP2A IC(50)=2.9+/-1.04 microM) and essentially equipotent with cantharidin (PP1 IC(50)=3.6+/-0.42 microM; PP2A IC(50)=0.36+/-0.08 microM). Cantharimides with non-polar or acidic amino acid residues are only poor inhibitors of PP1 and PP2A.

The First Two Cantharidin Analogues Displaying PP1 Selectivity

High pressure Diels-Alder reactions of furan and dimethylmaleate, and thiophene and maleimide resulted in two cantharidin analogues, 3 and 6 possessing PP1 selectivity (>40- and >30-fold selectivity) over PP2A. Both compounds exhibited moderate PP1 activity, 3 IC(50) 50 microM and 6 IC(50) 12.5 microM. Interestingly, the corresponding mono-ester derivatives of 3 showed no such selectivity.

Synthesis and Evaluation of a Molecularly Imprinted Polymer Selective to 2,4,6-Trichlorophenol

Molecularly imprinted polymers (MIPs) selective for the phenolic contaminant 2,4,6-trichlorophenol (2,4,6-TCP) were prepared and evaluated in three porogens of differing character (hexane, acetonitrile, dichloromethane). Rebinding of 2,4,6-TCP was found to be most effective in dichloromethane (imprinting factor: 13.2). Competitive binding studies performed against a range of close structural analogues showed a high preference for the target molecule, although partial recognition towards 2,4-dichlorophenol was also observed. Specificity was found to be dependent upon the presence of ring chlorine on the target, which suggested that these atoms participate in secondary binding interactions that are essential for successful recognition in the polymer cavity.

Substitution, oxidation and addition reactions at C-7 of activated indoles

Abstract 4,6-Dimethoxy-2,3-diphenylindole (1) undergoes acylation, bromination, oxidative coupling and acid-catalysed addition to aldehydes at C-7 to produce a range of 7-substituted indoles (3–11), the indolo-isatin (6), the 7,7′-bi-indolyls (14), (16), (18), and the 7,7′-di-indolylmethanes (20–31). Addition to cyclopentanone gave compound (32), while Michael addition to α,β-unsaturated ketones gave compound (33) and the non-benzenoid double adduct (34). Related reactions led to the formation of the ring-fused indoles (39) and (41). Some reactions of the related indole diester (2) are also reported.

Fruit-derived phenolic compounds and pancreatic cancer: Perspectives from Australian native fruits

ETHNOPHARMACOLOGICAL RELEVANCE Pancreatic cancer is a devastating cancer that presents late, is rapidly progressive and has current therapeutics with only limited efficacy. Bioactive compounds are ubiquitously present in fruits and numerous studies in vitro are addressing the activity of these compounds against pancreatic cancer, thus studies of specific bioactive compounds could lead to new anti-pancreatic cancer strategies. Australian native fruits have been used as foods and medicines by Australian Aboriginals for thousands of years, and preliminary studies have found these fruits to contain rich and diversified bioactive components with high antioxidant activity. Thus, Australian native fruits may possess key components for preventing or delaying the onset of tumorigenesis, or for the treatment of existing cancers, including pancreatic cancer. MATERIALS AND METHODS Numerous databases including PubMed, SciFinder, Web of Knowledge, Scopus, and Sciencedirect were analysed for correlations between bioactive components from fruits and pancreatic cancer, as well as studies concerning Australian native fruits. RESULTS In this review, we comprehensively highlight the proposed mechanisms of action of fruit bioactives as anti-cancer agents, update the potential anti-pancreatic cancer activity of various major classes of bioactive compounds derived from fruits, and discuss the existence of bioactive compounds identified from a selection Australian native fruits for future studies. CONCLUSION Bioactive compounds derived from fruits possess the potential for the discovery of new anti-pancreatic cancer strategies. Further, Australian native fruits are rich in polyphenols including some flora that contain unique phenolic compounds, thereby warranting further investigations into their anti-cancer properties.

Formulation of Cocaine-Imprinted Polymers Utilizing Molecular Modelling and NMR Analysis

Molecular imprinted polymers (MIPs) have distinctive features that make them attractive as an inexpensive, reusable, and robust field-based detection system for illicit substances. Optimizing MIP performance is traditionally attained by the synthesis and evaluation of a plethora of individual formulations. A non-covalently imprinted polymer for cocaine has been prepared using a commercially available molecular modelling package (Spartan 02) to predict energetically favourable monomer–template interactions between the target (T) and two different functional monomers (FM)—methacrylic acid (MAA) and 4-vinylpyridine (4VP). NMR studies undertaken to assess target–monomer behaviour in solution were in good agreement with the computational data. MIPs involving three target-to-functional monomer ratios (1 : 2, 1 : 6, and 1 : 14) were prepared and evaluated. Target rebinding was found to be most favourable in the 1 : 2 formulation with a target-selective binding of 0.48 ppm and an imprinting factor (I) of 2.8 obtained for 10 mg of test polymer.