Dear Mac Dz, if your goal is to find antibacterial activity, I recommend you to try with different solvents spanning the polar-non polar spectra, from water to CCl4 (if you ever assess activity of a non polar extract, you should disolve it in a DMSO solution first).

You can try with mixes also. In my experience, ethanol extraction followed by hot-water extraction (from the ethanol-extracted fraction after solvent evaporation) gives better results compared to ethanol alone or water alone. Even 70% ethanol (ethanol:water) yields extracts with higher activity.

I always assessed antibacterial activity against S. aureus, B. subtilis, P. aeruginosa, and E. coli, and activity against the Gram-negative ones was always unusual, likely because their outer membrane.

Best regards!

Methanol and Ethanol are not the same for the purpose of extracting plant materials. 

Although Methanol is more effective  for extraction.  Most studies use ethanol instead of methanol.  The advantage of ethanol is that it is much safer.

Dear Abdelraouf A. Elmanama 

Thanks for your answer.

But why did say methanol is more effective than ethanol for extraction?

It depends on the antimicrobial activity of the extract but with me Crocus sativus methanol extract is the better in a curent study of my group

The strength of solvent will determine which antimicrobial component you extract from the plant. It is the component or compound which should determine the zone of inhibition, although some components will be absorbed in the agar better. All this should  be balanced with proper experimental controls . ie the solvents should be fully evapourated before addition of the bacteria. There should be a control with no extract only solvent that has been evapourated . You could also have a series of extracts. Ethanol is considered a gentler extraction method and will not precipitate as many extracts from plants. Methanol will be slightly harsher and will also start to precipitate compounds which my not migrate/dissolve in the agar. You could add an intermediate extract of acetonitrile . Then after methanol extract you might try ethyl acetate . All these extractions can be done sequentially on the same material ie ethanol, acetonitrile, methanol, ethyl acetate etc or in batches on different material . You also might want to check that you are effectively extracting the plant material. Is it a soft plant or a hard plant ? the conditions for plants with tough cell walls obviously require a more vigorous mechanical extraction.

We can't give a response by ethanol or methanol. It's related to plant species used and microorganism.

methanol is more polar than ethanol, so the first extract more polar compounds than the second. But this not related to activity. The only way to get response is by testing the two solvents for your experiments using standard tests for crude extracts (agar diffusion). Then you can decide which solvent will be used for advanced tests.

Hi Mac, normally I use ethanol for extraction from plant tissue.

• The solvent selection used depends on the Partition coefficient (partition coefficient between water and octanol). The content of the extract from the compounds varies with the different solvent used.

• Ethyl alcohol and methanol alcohol

• Ethyl alcohol is less able to dissolve polar compounds such as phenols and others (compounds in general) - less toxic - easier to volatilize. Methyl alcohol is more efficient in dissolving polar compounds (compounds in general),Toxic, Difficult to evaporation.

• It suggested the use of methyl alcohol (probability of success in getting positive results higher)

From my previous experiment i investigated 2 plant species against E.coli. For the first plant the ethanol extract  showed MIC of 1.25 mg/ml and the methanol 0.62 mg/ml. For my second plant ethanol showed 0.31 mg/ml and methanol 0.62 mg/ml. I also used acetone extract and the MIC value was 0.15 mg/ml for the first plant and 0.31 mg/ml for the second plant. In your case i would suggest you try out the different solvents for extraction then you can draw a conclusion by yourself from your study. 

from the answer of Aitebiremen Gift Omokhua,  i recommended to use more solvent in your research no only methanol ( many solvent for one plant or many plant for one solvent)

Dear Aitebiremen Gift Omokhua

I agree with your response. However, in most literature I came across indicated that methanol gives better results for E.coli. 

Dear Mac Dz, if your goal is to find antibacterial activity, I recommend you to try with different solvents spanning the polar-non polar spectra, from water to CCl4 (if you ever assess activity of a non polar extract, you should disolve it in a DMSO solution first).

You can try with mixes also. In my experience, ethanol extraction followed by hot-water extraction (from the ethanol-extracted fraction after solvent evaporation) gives better results compared to ethanol alone or water alone. Even 70% ethanol (ethanol:water) yields extracts with higher activity.

I always assessed antibacterial activity against S. aureus, B. subtilis, P. aeruginosa, and E. coli, and activity against the Gram-negative ones was always unusual, likely because their outer membrane.

Best regards!

Dear Alejandro Piña Iturbe

One of the plant extracts I tested gave a zone of inhibition for only E. coli with no zones for S. aureus, B. subtilis, P. aeruginosa. This is somewhat unusual too.

please contact a natural chemist that can help with extractions It is a Whole different discipline than microbiology

Ethanol and methanol have practically the same extraction efficiency. Although methanol is more polar, it may present better results. However, keep in mind that methanol is more toxic.

I have tested aqueous extraction, ethanol, methanol, hexane, chloroform, acetone ... Particularly I prefer to use acetone. It is very polar like methanol, generally presenting better results in my studies against E. coli, S. aureus, B. cereus, X. axonopodis, S. marcescens and some fungi like A. niger.

Methanol is a stronger solvent than ethanol for the extraction of  bioactivw compounds that could show inhibitory properties against microorganisms. What i normally do when I am interested in potency and inhibitory properties is to extract with water, 70% ethanol, and carbon tetrachloride .

Philippa

ethanolic extract sure healthiest. 

methanol extract may contain some impurities.

DMSO would be good choice

Combine 1:1 ratio of dichloromane:methanol.This mixture of organic solvents extract both polar and non polar compounds from plant material.

methanol

Methanol , Hexane and ethanol are being used during extraction, but it could lead to some complications during antimicrobial test , that's why you can resolve it in DMSO to check for antimicrobial activity