Science Buddies: "Ask an Expert"

I have been working on a project for two years now on finding an alternative medicine for destroying E.coli.I took extracts from cranberries and garlic to see if they would work.The cranberry extract did work when I spun it down in the centrifuge and used the pellet.The thng that is troubling me is that I don't know what else I can do to increase the effect of the cranberry extract and how to further my experiment.If you have any suggestions can you please write back.

Hi Natalie,

Sounds like you have been doing some great work- well done! I would say that the next step is trying to isolate the components from your cranberry extract that have the anti-bacterial properties. This could be a long and complex process and the route you take will depend on what type of equipment you have available.

Perhaps to begin with you can describe what solvent you used before you centrifuged your extract and found that the active components were in the pellet? Did you try and other solvents to see if the results are different? What did you do to the pellet before you tested it for antibacterial activity?

Best of luck,
Caroline

In the beginning I blended fresh cranberries and boiled it in distilled water and it had no effect on the E.coli.Next,I chopped the cranberries into little pieces and let it sit in distilled water thinking that whatever is in the cranberries would diffuse into the water.I compared the cranberry extract to a garlic extractand the garlic extract made the E.coli grow.From the chopped up cranberries,after awhile some of the chunks started to settle at the bottom.So I took a sample from the bottom and spun it down in the centrifuge to get the pellet.I would use filter paper that was cut into small circles and put some of the pellet onto the paper and lay it on the E.coli which was in a petri dish.The next day I would check it and there would be a clear area around the filter paper which showed that the cranberry extract worked.If I wanted to see the reaction occur under a microscope what tools would I need to get instead of using slides?

Hi Natalie,
Good work! I believe that the technique that you are using is one of the more accepted ways to demonstrate antimicrobial activity.

May I suggest that you try soaking the cranberries in an organic solvent like acetone or alcohol? You may be able to extract other componets that cannot be extracted using water. As a control, however, make sure that you also set up when the filter paper only contains the solvent that you used. I hope this helps in expanding your research.

Natalie,

As an addendum to christinaleahkline's excellent suggestion to extract with one or more organic solvents, you may also try evaporating off the solvent and testing the residue that is left. This is usually done with a device called a "rotavapor" and these are usually found in organic chemistry labs. They distill off the solvent under a mild vacuum, leaving only the non-volatile substances that were dissolved in the solvent.

DO NOT try to distill off the organic solvent using a flame under a flask because the solvent is flammable and may explode. It is VERY DANGEROUS! That is why rotavapors exist, they do the same thing safely and neatly. Do this under professional supervision.

If your school does not have a rotavapor, go to your local college or university and try to convince an organic chemistry professor to help you with this part of your experiment. You will find that professors and scientists are usually happy to help with such things free of charge.

They may even be willing to help you see what is in the residue, especially if it has antimicrobial properties. You may even get a scientific publication out of it!