Researchers Lindi Heyns and Dr Charlotte Boucher are working together on an interdisciplinary project between the Departments of Zoology and Entomology and Veterinary Biotechnology at the University of the Free State (UFS). The focus of their research is on the preliminary biochemical description of skin secretions in some South African toads.

The project forms part of an Honours study executed by Dwayne Pike under Heyns’ supervision. He is co-supervised by Dr Boucher who is assisting with the biochemical and microbiological assays.

Dr Boucher said, “Amphibians are characterised by the presence of cutaneous glands spread over the skin. There are two types of glands, namely mucous and granular (poison), located on the inner surface of the epidermis. Mucous glands are widely dispersed over the skin, while granular glands can be grouped and enlarged in specific regions. Mucous glands are generally associated with maintenance of humidity and cutaneous respiration, whereas granular glands function in chemical defence against predators and/or microbial infection. Studies indicate that the compounds produced by the granular glands belong to numerous chemical classes with diverse pharmacological activities.”

The products secreted by granular glands are rich in low molecular weight constituents of varied molecular types, including proteins, peptides and toxins. These secretions make the toad foul-tasting to predators and even toxic to other frog species. In addition, amphibians offer an attractive source of novel antimicrobials. Studies indicate that as a response to inhabiting microorganism-rich environments they synthesise and secrete a diverse array of antimicrobial peptides (AMPs) as an innate form of defence. Extensive research by various other research groups has been carried out on antimicrobial peptides of the genus Rana; however, hardly any studies have investigated the antimicrobial activity of African frog species.

The focus of this preliminary project is to determine the protein composition of the glandular secretions of the Western olive toad (Amietophrynus poweri), using biochemical tests, such as SDS-PAGE also known as protein gel electrophoresis combined with mass-spectrometry used to identify unknown peptides and proteins. This will give us an overview of the composition of the glandular secretions. Furthermore, we are also looking at microbiological tests, which include assays that test for possible anti-microbial activity against various bacterial and fungal species.