Nonenzymatic Reactions in Natural Product Formation.

Biosynthetic mechanisms of natural products primarily depend on systems of protein catalysts. However, within the field of biosynthesis, there are cases in which the inherent chemical reactivity of metabolic intermediates and substrates evades the involvement of enzymes. These reactions are difficult to characterize based on their reactivity and occlusion within the milieu of the cellular environment. As we continue to build a strong foundation for how microbes and higher organisms produce natural products, therein lies a need for understanding how protein independent or nonenzymatic biosynthetic steps can occur. We have classified such reactions into four categories: intramolecular, multicomponent, tailoring, and light-induced reactions. Intramolecular reactions is one of the most well studied in the context of biomimetic synthesis, consisting of cyclizations and cycloadditions due to the innate reactivity of the intermediates. There are two subclasses that make up multicomponent reactions, one being homologous multicomponent reactions which results in dimeric and pseudodimeric natural products, and the other being heterologous multicomponent reactions, where two or more precursors from independent biosynthetic pathways undergo a variety of reactions to produce the mature natural product. The third type of reaction discussed are tailoring reactions, where postmodifications occur on the natural products after the biosynthetic machinery is completed. The last category consists of light-induced reactions involving ecologically relevant UV light rather than high intensity UV irradiation that is traditionally used in synthetic chemistry. This review will cover recent nonenzymatic biosynthetic mechanisms and include sources for those reviewed previously.

Discovery, Synthesis, and Biological Evaluation of Anaenamides C and D from a New Marine Cyanobacterium, Hormoscilla sp.

Our ongoing efforts to explore the chemical space associated with marine cyanobacteria from coral reefs of Guam have yielded two new members of the anaenamide family of natural products, anaenamides C (3) and D (4). These compounds were isolated from a novel Hormoscilla sp. (VPG16-58). Our phylogenetic profiling (16S rDNA) of this cyanobacterium indicated that VPG16-58 is taxonomically distinct from the previously reported producer of the anaephenes, VPG16-59 (Hormoscilla sp.), and other previously documented species of the genus Hormoscilla. The planar structures of 3 and 4 were determined via spectroscopic methods, and absolute configurations of the α-hydroxy acids were assigned by enantioselective HPLC analysis. To address the requirement for sufficient material for testing, we first adapted our published linear synthetic approach for 1 and 2 to generate anaenoic acid (7), which served as a point for diversification, providing the primary amides 3 and 4 from synthetic intermediates 5 and 6, respectively. The compounds were then tested for effects on HCT116 colon cancer cell viability and in an ARE-luciferase reporter gene assay for Nrf2 modulation using HEK293 human embryonic kidney cells. Our findings indicate that, in contrast to cytotoxic methyl esters 1 and 2, the primary amides 3 and 4 activate the Nrf2 pathway at noncytotoxic concentrations. Overall, our data suggest that the anaenamide scaffold is tunable to produce differential biological outcomes.

Discovery, Total Synthesis, and SAR of Anaenamides A and B: Anticancer Cyanobacterial Depsipeptides with a Chlorinated Pharmacophore.

New modified depsipeptides and geometric isomers, termed anaenamides A (1a) and B (1b), along with the presumptive biosynthetic intermediate, anaenoic acid (2), were discovered from a marine cyanobacterium from Guam. Structures were confirmed by total synthesis. The alkylsalicylic acid fragment and the C-terminal α-chlorinated α,ß-unsaturated ester are novelties in cyanobacterial natural products. Cancer cell viability assays indicated that the C-terminal unit serves as the pharmacophore and that the double-bond geometry impacts the cytotoxicity.

Isolation and Characterization of Anaephenes A-C, Alkylphenols from a Filamentous Cyanobacterium ( Hormoscilla sp., Oscillatoriales).

Three related new alkylphenols, termed anaephenes A-C (1-3), containing different side chains, were isolated from an undescribed filamentous cyanobacterium (VPG 16-59) collected in Guam. Our 16S rDNA sequencing efforts indicated that VPG 16-59 is a member of the marine genus Hormoscilla (Oscillatoriales). The structures of anaephenes A-C (1-3) were elucidated by spectroscopic methods, and compounds assayed for growth inhibitory activity against prokaryotic and eukaryotic cell lines. Anaephene B (2), possessing a terminal alkyne, displayed moderate activity against Bacillus cereus and Staphylococcus aureus with MIC values of 6.1 µg/mL. While 1 and 3 showed no pronounced activity in these assays, their structural features highlight the unusual biosynthetic capacity of this cyanobacterium and warrant further study.

Iodinated Meroditerpenes from a Red Alga Callophycus sp.

Unique iodine-containing meroditerpenes iodocallophycoic acid A (1) and iodocallophycols A-D (2-5) were discovered from the Fijian red alga Callophycus sp. Because flexibility of the molecular skeleton impaired full characterization of relative stereochemistries by NMR spectroscopy, a DFT-based theoretical model was developed to derive relevant interproton distances which were compared to those calculated from NOE measurements, yielding the relative stereochemistries. The correct 2S,6S,7S,10S,14S enantiomers were then identified by comparison of theoretical and experimental ECD spectra. Biological activities of these iodinated and brominated meroditerpenes and additional new, related bromophycoic acid F (6) and bromophycoic acid A methyl ester (7), were evaluated for relevant human disease targets. Iodocallophycoic acid A (1) showed moderate antibiotic activity against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VREF) with MIC values of 1.4 and 2.2 µg mL-1, respectively. It also potentiated the anti-MRSA activity of oxacillin in a synergistic fashion, resulting in an 8-fold increase in oxacillin potency, for a MIC of 16 µg mL-1.

An island of compassion.

This narrative describes the experience of a palliative care physician from Australia visiting the palliative care service at a cancer hospital in India. The place of compassion in an environment of limited resources is discussed.

The effectiveness and adverse effects profile of "burst" ketamine in refractory cancer pain: The VCOG PM 1-00 study.

This multi-centre study of adjuvant "burst" ketamine in palliative care in-patients documents its effectiveness, duration of pain relief, and adverse effects (AE) profile. Patients received a three-to-five day continuous subcutaneous infusion (CSCI) of ketamine escalated from 100 to 300 to 500 mg/24 hours if required. When the effective or maximum tolerated dose was attained, the infusion was continued for three days and each patient assessed as a responder or non-responder using strict criteria. The response rate was 22/44 (50 percent), with 4 (9 percent) becoming pain-free. Pain relief lasting two or more weeks was documented in 50 percent of responders. AEs were documented daily using the National Cancer Institute (NCI) Common Toxicity Criteria 0-4 scales. There were 11 grade 3 and 4 neurological AEs. However, no responders elected to cease treatment early due to neurological AEs. We concluded that this protocol in the controlled environment of an in-patient PC unit is relatively safe and simple with reasonable effectiveness.

Improving access to clinical information in after hours community palliative care.

OBJECTIVE: To improve access to clinical information for nurses and doctors providing after hours community palliative care in a regional Australian setting. DESIGN: This was an action research project designed to improve collation and distribution of succinct, pertinent and timely information about unstable palliative care patients to nurses and general practitioners (GPs) involved in after hours care. Each week day, each patient's purpose-designed single-page information sheet was updated on the community palliative care service computers. This sheet was designed to give key abstracted information on each patient's history, current condition, treatment and plans for future care. Patients considered to be unstable had their sheets faxed to the GPs on call. SETTING AND SUBJECTS: This procedure was followed for all adult patients admitted to Ballarat Hospice Care Inc, Victoria, Australia between June and August 2004. The nurses and Executive Officer at Ballarat Hospice Care Inc and thirteen GPs from the Ballarat and District Division of General Practitioners were involved in the study. MAIN OUTCOME MEASURES: Surveys and feedback from palliative care nurses and GPs. RESULTS: A one-page information sheet provided essential clinical information to nurses and doctors. The nurses' confidence markedly increased with ready access to the information sheets on a hand held Palm Pilot. The nurses also reported improved outcomes for patients using this approach and there was favourable feedback from GPs. CONCLUSIONS: This project led to the development of a simple, effective and low cost means of improving communication between professionals caring for palliative care patients after hours.

Advance directives in action in a regional palliative care service: "road testing" the provisions of the Medical Treatment Act 1988 (VIC).

In order to explore the usefulness and acceptability of the provisions of the Medical Treatment Act 1988 (Vic) for palliative care patients in a rural region in Victoria, Australia, between July and December 2004 patients were given information explaining the Act and the opportunity to discuss it with the research officer. Grounded theory methodology was used to evaluate client responses. Findings suggested that palliative care patients are willing to engage in advance care planning but they have to be well enough and need skilled, practical, face-to-face assistance to complete the required legal forms. Written materials alone are not adequate, but provide the opportunity for medical staff to have conversations about death and dying. Doctors and nurses should understand the provisions of the Act to assist patients and families. It is recommended that advance care planning, appropriate to the jurisdiction, be an integral part of the palliative care assessment process.

Evaluation of training on the use of Graseby syringe drivers for rural nonspecialist nurses.

AIM: to assess the impact of a training programme on nurse confidence in: setting up the Graseby syringe driver (GSD); explaining the GSD to patient and family; setting the rate on the GSD; putting appropriate type and dose of drugs in the GSD. STUDY DESIGN: training programme with pre-training, post-training and follow-up questionnaires. SAMPLE AND SETTING: palliative care nurse consultants presented half-day training sessions to 270 non-specialist nurses throughout the rural Grampians Health Region of Victoria, Australia. Nurses were from rural acute and sub-acute care settings, aged care facilities, and district nursing and nurse education services. MEASUREMENTS: demographic details of participants, previous experience and training with GSDs, comparative analyses of the four confidence parameters and participants' assessment of interest, new knowledge and usefulness of the training programme. RESULTS: increases in confidence levels were found in participating nurses in relation to each of the four confidence parameters. A follow-up survey tested residual benefit three months after the training programme. Statistically significant variations were found in nurses' confidence levels in relation to frequency of use. CONCLUSIONS: regular use of, and/or refresher sessions about the GSD are recommended to maintain optimum confidence, effective and safe nursing use of the GSD in palliative care.