There are four types of poisonous frogs known to secrete lipid‑soluble alkaloids derived from their food. The discovery of these skin alkaloids in a fifth species in Cuba could provide new clues to these amphibians’ evolution.Amphibians accumulate a variety of compounds in their skins, many of which act as a defence against microorganisms and predators. Of these compounds, 800 have been identified as lipid-soluble alkaloids; but despite the wide variety, the alkaloids occurrence is restricted to a small but diverse group of frog species. 

During fieldwork in Cuba studying dwarf frogs, the odour of dissected specimens reminded researchers of alkaloid-containing species and so they tested the skins using GC-MS. Analysis revealed the presence of eight alkaloid compounds, some of which researchers also found in mites and ants that the frogs had eaten.

Previous studies have noted correlations between alkaloids in the skin, small body size, small prey and colourful skin to warn predators but the order these traits evolved in has been unclear. However, dietary sources for these alkaloids, as suggested by this research, favours a scenario where the frogs specialized in smaller prey first, which then lead to them becoming poisonous.

1.  A. Rodriguez et al., Biol. Lett., 6 (2010).

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There are four types of poisonous frogs known to secrete lipid?soluble alkaloids derived from their food. The discovery of these skin alkaloids in a fifth species in Cuba could provide new clues to these amphibians? evolution.

Poisonous dwarf frogs

The United States Food and Drug Administration in Irvine, California, USA has purchased the Dionex ICS-5000 ion chromatography system with mass spectrometer for the analysis of biogenic amines in fish samples. 

Consumption of large amounts of biogenic amines, such as histamine, putrescine and cadaverine, can lead to allergic reactions in some individuals, and can also be life threatening in some cases. The US FDA has established a defect action level of 50 mg/kg histamine and a toxicity level of 500 mg/kg histamine in fish.

According to the manufacturer, the system is ideal for IC–MS analysis and applications of this type. The system flexibility and modularity is reported to provide the ability to analyse samples at capillary, microbore or standard flow-rates (or any combination of two in a dual system), and to configure an ion chromatography system specifically for the required solutions.

A range of food testing application notes are available from the company’s website, 

 under Markets/Food and Beverage/Food Safety.

The United States Food and Drug Administration in Irvine, California, USA has purchased the Dionex ICS-5000 ion chromatography system with mass spectrometer for the analysis of biogenic amines in fish samples.

The inspector's detector

Organic food has increased in popularity over recent years, with environmental protection, increased animal welfare, taste and freshness all cited as important reasons for this demand. Whether organic produce provides any actual health benefits is still controversial, and a recent study of organic carrots, onions and potatoes has claimed that the process may add nothing at all.

Differences between organic and conventional agricultural processes can affect the nutrient content of plants; however previous studies have generated conflicting results. Many of these failed to take geographical locations and growth season into account, which a study published in the 

Journal of Agricultural and Food Chemistry

A group of bioactive secondary plant metabolites called polyphenols have been speculated to have positive health effects, including a decreased risk of heart diseases, dementia and cancer. The study compared selected polyphenols — flavonoids and phenolic acids — to determine the effect of the growth systems. Plants were analysed by pressurized liquid extraction and high‑performance liquid chromatography–ultraviolet quantification and seven flavonoids were detected in onions as well as one and three phenolic acids in carrots and potatoes, respectively. A significant year-to-year variation of one flavanoid in onions was observed but according to the study no other significant differences between systems was found.

According to the researchers, “on the basis of the present study carried out under well-controlled conditions, it cannot be concluded that organically grown onions, carrots and potatoes generally have higher contents of health‑promoting secondary metabolites in comparison with the conventionally cultivated ones.”

1.  M. Soltoft et al., J. Agric. Food Chem., 58, 10323–10329 (2010).

Whether organic produce provides any actual health benefits is still controversial, and a recent study of organic carrots, onions and potatoes has claimed that the process may add nothing at all.

Healthy eating?

KNAUER has donated a high-quality analyser to the Hamburg University of Technology (TUHH) for use in education and training in the chemical engineering department. The company provided a Smartline HPLC system that the company reports will allow process engineers studying at TUHH to learn how to use this technology during their studies, before they enter the professional marketplace.

“We want to introduce students to interdisciplinary research early on, as is typical of the TUHH. The instrumentation donated by KNAUER enables our future engineers to become familiar with modern analysis methods at the interface of chemistry and chemical engineering”, said Professor Andreas Liese at the donation ceremony in Hamburg.

“The use of modern analytical instruments is very important for future engineers. We are pleased to support a higher standard of education at the TUHH with our donation”, said the company’s managing director, Dr Alexander Bünz, himself a former engineering student at TUHH in the 80s and one of the first to receive a doctorate from the university in 1995.

KNAUER has donated a high-quality analyser to the Hamburg University of Technology (TUHH) for use in education and training in the chemical engineering department.

HPLC donation

Analysing a complex mixture of unknown macromolecules and low molar mass compounds is often challenging in GPC/SEC. A disadvantage of the most commonly used detector, the very universal but unspecific refractive index (RI) detector, is that this detector only provides concentration information and no information about the chemistry. In addition, various positive and negative peaks besides the pure sample peaks in a GPC/SEC run are normal.However, only when the chemical structures of the polymer components are known can sophisticated separation techniques, such as GPC/SEC, liquid adsorption chromatography (LAC) or liquid adsorption chromatography under critical conditions (LACCC) be properly adapted. Also, advanced detection such as on-line light scattering or triple detection requires the knowledge of the chemistry, since these techniques need specific sample related constants (e.g., the refractive index increment dn/dc).Therefore peak identification or substance identification can be very important in GPC/SEC, especially when establishing new methods. There are several possibilities for GPC/SEC users to identify peaks or to learn more about sample chemistry.

Peak identification or substance identification can be very important in GPC/SEC, especially when establishing new methods.

Tips & Tricks: GPC/SEC Peak Identification in GPC/SEC

A comprehensive review of a selection of companies’ most instrumental innovation/research or scientific breakthrough in 2010.

A comprehensive review of a selection of companies? most instrumental innovation/research or scientific breakthrough in 2010.

The Column-12-07-2010

Poisonous dwarf frogs

The inspector's detector

Healthy eating?

HPLC donation

Tips & Tricks: GPC/SEC Peak Identification in GPC/SEC

Instrumental Innovations