Substances with antimalarial properties found in marine organisms
Researchers from the IBEC/ISGlobal joint Nanomalaria Unit and the Nanoscience and Nanotechnology Institute (IN2UB), have shown that certain sugars (sulphated polysaccharides) obtained from marine organisms disable the growth of the Plasmodium falciparum, one of the parasites causing malaria when it inhibits its ability to invade red blood cells (erythrocytes). The results, published on the magazine Scientific Reports, open new ways to the development of antimalarial drugs against which Plasmodium cannot seem to show resistance.
Researchers from the IBEC/ISGlobal joint Nanomalaria Unit and the Nanoscience and Nanotechnology Institute (IN2UB), have shown that certain sugars (sulphated polysaccharides) obtained from marine organisms disable the growth of the Plasmodium falciparum, one of the parasites causing malaria when it inhibits its ability to invade red blood cells (erythrocytes). The results, published on the magazine Scientific Reports, open new ways to the development of antimalarial drugs against which Plasmodium cannot seem to show resistance.
When the malaria parasite enters the blood circulation, it invades the liverʼs cells to produce thousands of merozoites (a life stage of the Plasmodium parasite). These merozoites get back in the circulation, where they infect the red blood cells and escape the immune systemʼs control. It has been known since long ago that some biomolecules such as heparin can block the adhesion and entrance of the merozoites in the red blood cells; however the heparin is not a good therapeutic candidate because the quantity that the malaria treatment needs could provoke internal bleeding.
In this study, the authors explored the antimalarial capacity of sulphated polysaccharides similar to heparin, derived from sea cucumbers, red algae and marine sponges, and they found that those compounds inhibit significantly the growth of P. falciparum even at a low concentration with no anticoagulant activity. Moreover, most of the compounds that were analysed increased the survival of infected mice with another Plasmodium type, and they could see the appearance of antibodies against the parasite in even some of the infected mice, which suggests that by lingering the invasion of red blood cells the generation of an immune response against the parasite can be favoured.
According to Joana Marques, researcher of the IBEC/ISGlobal joint unit and main author of the article: “the marine organisms are a rich source of sulphated polysaccharides similar to heparin”. “Such molecules have anticoagulant activities small enough to be used in circulating blood at their active concentrations without incurring the risk of internal bleeding”, says Marques.
“In the in vitro experiments we did in these compounds, there was a significant inhibition of Plasmodium falciparum, even at low-anticoagulant concentrations, and preliminary in vivo assays in mice look certainly promising” says Xavier Fernández-Busquets, responsible of the IBEC/ISGlobal joint unit and member of IN2UB. “These compounds slow down the invasion of red blood cells by Plasmodium and perhaps the resulting prolonged exposure of the parasite to circulating lymphocytes gives the immune system a stronger chance to build up defences” concludes the researcher.
This discovery means that heparin-related molecules can be considered and explored for the design of new therapeutic focuses against malaria where low-activity polysaccharides could play a dual-role; as drugs inhibiting the growth of the parasite and at the same time, promoting the immune response against the same one.