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Halloween is usually a time of ghosts, ghouls, witches and carving scary faces into pumpkins. Well, a team of South Korean researchers has now discovered that pumpkins can ward off more than just spectres, by isolating a novel anti-fungal protein from pumpkin rinds. Many species of plant naturally produce anti-microbial proteins, including various chitinases, proteinase-inhibitors and plant defensins. With bacterial and fungal pathogens increasingly developing resistance to current antibiotics, scientists have been looking to plants as a potential source of the next generation of antibiotics and fungicides. And this includes pumpkins. For as well as being a tasty food and providing a good home for a lantern, pumpkins confer a number of health benefits. Their seeds are a good source of vitamins and essential minerals, while certain chemical compounds extracted from pumpkins appear to promote the regeneration of damaged pancreatic tissue. Scientists have also already found several proteins displaying anti-microbial activity in pumpkin leaves and seeds. So a team led by Kyung-Soo Hahm from Chosun University in Kwangju decided to search for anti-microbial proteins in the thick, creased outer rind of pumpkins. To determine whether or not this would be a worthwhile endeavour, they first tested the anti-microbial ability of a crude extract of the rind. This revealed that pumpkin rind is good at killing fungi but not bacteria. To isolate the protein responsible for this anti-fungal activity, Hahm and his team passed the extract through a cation exchange chromatography column. Antimicrobial proteins tend to have fairly high isoelectric points, which means that they have a positive charge at low pHs and so will bind with cation exchange stationary phases. This split the extract into four fractions, with only the second fraction displaying any anti-fungal activity. Hahm and his team then analysed this fraction with reversed-phase high performance liquid chromatography and gel electrophoresis, finding that it only produced a single peak in the chromatograph and a single band in the gel. This indicated that the anti-microbial activity was due to a single protein, which the scientists had successfully isolated. They next tested this isolated protein on 10 species of fungi. These included species such as Fusarium oxysporum and Trichoderma harzianum, which cause important diseases in crop plants, and Candida albicans, which can infect humans. The protein proved able to control all of them, but had no effect on the bacteria Escherichia coli and Staphylococcus aureus, both of which can infect humans. More fortuitously, it also proved to have no detrimental effect on human red blood cells. Finally, Hahm and his team attached the fluorescent dye rhodamine to the protein. They then used confocal laser scanning microscopy to spy on the protein as it interacted with the fungi C. albicans and Fusarium solani. This revealed that, as with many natural antimicrobial compounds, the protein seems to kill fungi by punching holes in their outer membranes. Based on these findings, Hahm and his team conclude that this pumpkin-derived protein could be developed as a novel anti-fungal agent and also potentially be used to produce genetically-modified crop plants that are naturally resistant to fungal diseases. So this Halloween remember that pumpkins are much more than just scary lantern-holders. Related links:
The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd. |
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