Polygodial-induced noradrenaline release in human neuroblastoma SH-SY5Y cells

Anti-Yeast Synergistic Effects and Mode of Action of Australian Native Plant Essential Oils

Yeasts are the most common group of microorganisms responsible for spoilage of soft drinks and fruit juices due to their ability to withstand juice acidity and pasteurization temperatures and resist the action of weak-acid preservatives. Food industries are interested in the application of natural antimicrobial compounds as an alternative solution to the spoilage problem. This study attempts to investigate the effectiveness of three Australian native plant essential oils (EOs) Tasmanian pepper leaf (TPL), lemon myrtle (LM) and anise myrtle (AM) against weak-acid resistant yeasts, to identify their major bioactive compounds and to elucidate their anti-yeast mode of action. The minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC) and minimum bactericidal concentration (MBC) were assessed for EOs against weak-acid resistant yeasts (Candida albicans, Candida krusei, Dekkera anomala, Dekkera bruxellensis, Rhodotorula mucilaginosa, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Zygosaccharomyces bailii and Zygosaccharomyces rouxii) and bacteria (Staphylococcus aureus and Escherichia coli). The EOs showed anti-yeast and antibacterial activity at concentrations ranging from 0.03–0.07 mg/mL and 0.22–0.42 mg/mL for TPL and 0.07–0.31 mg/mL and 0.83–1.67 mg/mL for LM, respectively. The EOs main bioactive compounds were identified as polygodial in TPL, citral (neral and geranial) in LM and anethole in AM. No changes in the MICs of the EOs were observed in the sorbitol osmotic protection assay but were found to be increased in the ergosterol binding assay after the addition of exogenous ergosterol. Damaging of the yeast cell membrane, channel formation, cell organelles and ion leakage could be identified as the mode of action of TPL and LM EOs. The studied Australian native plant EOs showed potential as natural antimicrobials that could be used in the beverage and food industry against the spoilage causing yeasts.

Drug-induced permeabilization of S. cerevisiae

Budding yeast are not permeable to many drugs. This unit provides a protocol in which polygodial is used to permeabilize the cell membrane, thereby allowing budding yeast cells to be treated with drugs that otherwise would be ineffective.

Development of an in vitro test battery for the estimation of acute human systemic toxicity: An outline of the EDIT project. Evaluation-guided Development of New In Vitro Test Batteries

The aim of the Evaluation-guided Development of new In Vitro Test Batteries (EDIT) multicentre programme is to establish and validate in vitro tests relevant to toxicokinetics and for organ-specific toxicity, to be incorporated into optimal test batteries for the estimation of human acute systemic toxicity. The scientific basis of EDIT is the good prediction of human acute toxicity obtained with three human cell line tests (R(2) = 0.77), in the Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) programme. However, the results from the MEIC study indicated that at least two other types of in vitro test ought to be added to the existing test battery to improve the prediction of human acute systemic toxicity - to determine key kinetic events (such as biotransformation and passage through biological barriers), and to predict crucial organ-specific mechanisms not covered by the tests in the MEIC battery. The EDIT programme will be a case-by-case project, but the establishment and validation of new tests will be carried through by a common, step-wise procedure. The Scientific Committee of the EDIT programme defines the need for a specific set of toxicity or toxicokinetic data. Laboratories are then invited to perform the defined tests in order to provide the "missing" data for the EDIT reference chemicals. The results obtained will be evaluated against the MEMO (the MEIC Monograph programme) database, i.e. against human acute systemic lethal and toxicity data. The aim of the round-table discussions at the 19th Scandinavian Society for Cell Toxicology (SSCT) workshop, held in Ringsted, Denmark on 6-9 September 2001, was to identify which tests are the most important for inclusion in the MEIC battery, i.e. which types of tests the EDIT programme should focus on. It was proposed that it is important to include in vitro methods for various kinetic events, such as biotransformation, absorption in the gut, passage across the blood-brain barrier, distribution volumes, protein binding, and renal clearance/accumulation. Models for target organ toxicity were also discussed. Because several of the outlier chemicals (paracetamol, digoxin, malathion, nicotine, paraquat, atropine and potassium cyanide) in the MEIC in vivo-in vitro evaluation have a neurotoxic potential, it was proposed that the development within the EDIT target organ programme should initially be focused on the nervous system.

Toxicodynamic modelling and the interpretation of in vitro toxicity data

The results of in vitro toxicity experiments are not easily extrapolated to 'toxicological risk' for an intact organism. One of the most obvious differences between the situation in vitro and in vivo is the absence of the processes of absorption, distribution, metabolism and excretion that govern the exposure of the target tissues of the organism in vivo. The development of biokinetic models is aimed at estimating the relevant target tissue concentration of a compound. In our study, biokinetic models were constructed, where possible, solely on the basis of in vitro derived parameters for biotransformation as well as on partition coefficients determined or calculated from physicochemical structures. Another requirement is the existence of appropriate in vitro biological systems for the measurement of relevant effects. This requires a thorough knowledge of the possible mechanisms of toxic action, and of the physiology of the target organs. When these prerequisites are met (i.e. when the appropriate parameters can be quantified in a non-animal system), then an estimate of the dynamics in vitro can be made (e.g. as a critical active concentration). This will then result in a model describing a compound's dynamics. Eventually, the result of biokinetic and toxicodynamic models will need to be integrated in a compound's hazard and/or risk evaluation. A study carried out in the ECITTS programme showed promising results for the estimation of the acute and chronic systemic toxicity of a number of neurotoxic compounds.