Antimicrobial properties of plant extracts

Peter Sigsworth

COMMITTEE
We seem to struggle to get this to work - basically you mix the dried ground plant material with IDA (3g in 10ml IDA) - for example ground white pepper, ground chili powder, ground cumin etc.
Spread a lawn of bacteria on nutrient agar and place discs impregnated with the extract on the lawn.
We've tried Micrococcus Luteus and E.Coli both seem not to be bothered by any of the extracts.
Has anybody got this to work and if so what bacteria and how did you make up your extracts/impregnated discs?
 
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Peter Sigsworth

COMMITTEE
I've not done anything like this but, just off the top of my head, might something like Yakult work?
Do you mean growing the yakult as the lawn instead of the recommended bacteria in which case what type of agar? As I don't think yakult will grow on nutrient agar.
 

karen b

COMMITTEE
I've not done anything like this but, just off the top of my head, might something like Yakult work?

There is a practical like this using Yakult. One of our techs prepped plates for the A level Food Tech students based on worksheets from the Society for Microbiology
 
One of my classes just did this experiment and we found that B. subtilis works great.

The extracts we used were clove oil (I found an ancient bottle from the 1970s in the prep room cupboard haha), garlic glove, garlic leaf (both of which were ground up by the students with pestle&mortar and this fulfills the requirement that the students obtain their own extract) and the fourth one was honey.

The results were that clove oil worked the best, complete occlusion zone about a full 1cm around the disk, then garlic clove and leaf were about equal with occlusion zones about half a cm and honey was the 'trick' which actually had more growth than the rest of the lawn. It gave the kids good results to think about especially because the honey was manuka honey which is marketed as being exceptionally antimicrobial haha.

For one of the classes they were having difficulty getting it to work so i put about half a dropper full (2ml) of dettol spray into the pestle and mortar with the garlic clove in it and said it was a 'cell lysis accelerant' which is technically not incorrect and helped give a clearer result :p
 

Peter Sigsworth

COMMITTEE
Thanks all so far. You have given me ideas to change the practical so it works - but has anyone got it to work as per EDEXCEL GCSE (9-1) guide SB5g.1.
I suspect that using oils are incredibly concentrated whereas the 'tech' guide says to mix 3g of ground plant material with 10ml IDA - It looks like we have another case of an exam board setting a practical which doesn't work!!!
 

Peter Sigsworth

COMMITTEE
One of my classes just did this experiment and we found that B. subtilis works great.

The extracts we used were clove oil (I found an ancient bottle from the 1970s in the prep room cupboard haha), garlic glove, garlic leaf (both of which were ground up by the students with pestle&mortar and this fulfills the requirement that the students obtain their own extract) and the fourth one was honey.

The results were that clove oil worked the best, complete occlusion zone about a full 1cm around the disk, then garlic clove and leaf were about equal with occlusion zones about half a cm and honey was the 'trick' which actually had more growth than the rest of the lawn. It gave the kids good results to think about especially because the honey was manuka honey which is marketed as being exceptionally antimicrobial haha.

For one of the classes they were having difficulty getting it to work so i put about half a dropper full (2ml) of dettol spray into the pestle and mortar with the garlic clove in it and said it was a 'cell lysis accelerant' which is technically not incorrect and helped give a clearer result :p
Did you use the neat garlic clove or did you dissolve it in a liquid?
 
Thanks all so far. You have given me ideas to change the practical so it works - but has anyone got it to work as per EDEXCEL GCSE (9-1) guide SB5g.1.
I suspect that using oils are incredibly concentrated whereas the 'tech' guide says to mix 3g of ground plant material with 10ml IDA - It looks like we have another case of an exam board setting a practical which doesn't work!!!
We have done this for years Peter using ground plant material. Garlic, cloves, lavender, rosemary & mint, most work really well. We are doing it again in a couple of months. For the garlic I used a press & gave them the paste. We also only use enough IDA to mix with the material, just a few drops.
One student did an individual practical using different honeys,including Manuka., they were ok, but I think we concluded that a lot of the result came form the high concentration of sugar in the honey.
For bacteria we use E Coli B & M Luteus.
 

Peter Sigsworth

COMMITTEE
We have done this for years Peter using ground plant material. Garlic, cloves, lavender, rosemary & mint, most work really well. We are doing it again in a couple of months. For the garlic I used a press & gave them the paste. We also only use enough IDA to mix with the material, just a few drops.
One student did an individual practical using different honeys,including Manuka., they were ok, but I think we concluded that a lot of the result came form the high concentration of sugar in the honey.
For bacteria we use E Coli B & M Luteus.
That sounds great - it is clear that the set method isn't fit for purpose as the extracts aren't concentrated enough - I will either use neat oils or as you have done make up the extracts with a minimum of solvent (far less than the tech guide requires). Many thanks.
 
Did you use the neat garlic clove or did you dissolve it in a liquid?

As neat as possible, we didn't suspend anything in IDA it was just biffed up in a pestle and mortar with the smallest amount of de-ionised water possible to get it ground up. Depends on your garlic of course as some cloves have higher liquid content than others.

Everything else was neat, just enough of each material to saturate the little disks. If theres time I think it would be beneficial to leave the disks to soak in their chosen liquid for a while to ensure they are all fully saturated.
 
We seem to struggle to get this to work - basically you mix the dried ground plant material with IDA (3g in 10ml IDA) - for example ground white pepper, ground chili powder, ground cumin etc.
Spread a lawn of bacteria on nutrient agar and place discs impregnated with the extract on the lawn.
We've tried Micrococcus Luteus and E.Coli both seem not to be bothered by any of the extracts.
Has anybody got this to work and if so what bacteria and how did you make up your extracts/impregnated discs?
Mint and Garlic cloves ground in a mortar and pestle work well, there is an edexcel A Level protocol for this.
Salters-Nuffield Advanced Biology Resources Activity 4.22
 
As neat as possible, we didn't suspend anything in IDA it was just biffed up in a pestle and mortar with the smallest amount of de-ionised water possible to get it ground up. Depends on your garlic of course as some cloves have higher liquid content than others.

Everything else was neat, just enough of each material to saturate the little disks. If theres time I think it would be beneficial to leave the disks to soak in their chosen liquid for a while to ensure they are all fully saturated.
Same here, although the garlic press is a revelation, so much easier.
 

Peter Sigsworth

COMMITTEE
Well, I've learned and awful lot today with this one and the 'malt extract' thread. Thank you all so very much - I can save money as well as get better results form our temperamental experiments and that's what this forum is all about for me.
 
We seem to struggle to get this to work - basically you mix the dried ground plant material with IDA (3g in 10ml IDA) - for example ground white pepper, ground chili powder, ground cumin etc.
Spread a lawn of bacteria on nutrient agar and place discs impregnated with the extract on the lawn.
We've tried Micrococcus Luteus and E.Coli both seem not to be bothered by any of the extracts.
Has anybody got this to work and if so what bacteria and how did you make up your extracts/impregnated discs?
Thats true! If I was making it for the students I would use that but they all have to do it themselves and we already have tonnes of pestle and mortars
Same here, although the garlic press is a revelation, so much easier.
Try Thyme as an antimicrobial - it's extremely potent.:);)
 
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