Ciku antimicrobial activity report

After I did some extraction last week, I gave a bottle of the frozen extract to another researcher for an antimicrobial activity pre-test. My objective is to see whether how much, and at what concentration, is the activity in Ciku extract.

The researcher, Cindy, proposed a pretest using the method she is familiar with, which is outlined below:

1. Saline and media is prepared, around 30 plates. Media: Mueller-Hinton.
2. Microorganism is isolated, around 100 microliter into a saline and adjusted with McFarland standard.
3. 100 microliter of the mircoorganism is streaked on plates of Mueller-Hinton agar.
4. A dilution of the extract is done at 0%, 50%, and 25% dilution level.
5. 1000 microliter of each diluted extract is pipetted into three 6.00mm filter paper disks.
6.  Disks are placed on the media carefully with forceps.
7. The plates are incubated for 16-18 hours in 37C.
8. Clear zones is measured, if any, and recorded in mm.

 And, the results are given as below:

So as you can see here, the ciku is compared with a control antibiotic. The inhibition zone is under 20 mm for ciku extract while the antibiotic is above 40mm. According to standard, this can be translated to antimicrobial activity as follows:

Not effective	10 or less
intermediate	11 to 15
effective	16 or more

Therefore, the ciku is between intermediate and not effective. But mostly, not effective.

How is this so, especially when ciku has been proven to have anticancer activity as shown in breast cancer cells (Jayakumar and Kanthimathi, 2011) and colon cancer cells (Ma et al, 2003)? In these studies as well, it is explained that the activity is attributed to its polyphenols and flavonoids, which is proven to have an antimicrobial activity (Daglia, M., 2011) 

Therefore, what happens here may be attributed to an error for example, due to difference in method or experiment excecution. For example, extraction is done following exactly the one outlied in the 2011 research. However, the fruit maturity level chosen may be different since it is not stated in the research. Also, the length of exposure to light and air may destroy the polyphenols.

Another thing is that the method of antimicrobial activity may not be suitable for the type of extract. In a research on ginger as shown here (Sebiomo et al, 2010) , water extract are done using disk diffusion while ethanol extract is done using agar well. Therefore using disk diffusion, ethanol extracts of ciku may not have diffused fully onto the agar.

A suggestion is to do the experiment again with another sample extraction, to see whether this is just experimental error; or to do a newer extraction with less mature fruits.

Table from:
Johnson, T. and C. Case, 1995. "Chemical Methods of Control," adapted from Laboratory Experiments in Microbiology, Brief Edition, 4th ed. Redwood City, CA: Benjamin/Cummings Publishing Co., available online from The National Health Museum, Access Excellence Activities Exchange http://www.accessexcellence.org/AE/AEC/CC/chance_activity.html.