Dear

The phenolic compounds have good antimicrobial activities with different mechanisms of action. Other types of compounds also revealed such activity. Phenolic compounds usually isolated with high amounts in ethanol/ water mixture 70 to 80 usually. Methanol is more polar than ethanol so less amounts of non polar compounds can isolated specially steroids which may have activity. if you have no clue about the specific active compounds  you can use different solvents to extract the active constituents. You can start with non polar solvent to end up with polar solvent e.g. chloroform, the residue can be subjected to extraction by ethyl acetate, then the residue can be extracted with methanol. With 24 hour for each. With this methodology you can really know if your plant have any activity or not. And also have a little information about the polarity of the active compounds, which can help you in the isolation process.

Regards

Dear Sony,

Actually we can not generalize the best solvent to extract the antimicrobial compounds from plant material, the consideration is according to the solubility of the antimicrobial compounds it self. But if you are questioning about the best solvent, as general, water always the best, because water just has a litle bit potential to interupt or interfere the activity of active compound, in this case is antimicrobial activity. Some other solvent will affect the antimicrobial activity or even the solvent also has the antimicrobial activity, and it will interfering your antimicrobial activity determination

Dear

Water can not isolate a large group of organic substances, which they responsible for the most known activities. The use of organic solvents was a great step in drug discovery. However, active solvent like ethanol can be removed by using rotary evaporator.

removing ethanol from your extract will change the solubility behavior of your extract solution, and some of chemical compound will change from soluble into insoluble, so your extract solution is becoming unclear and inhomogenous. This condition of solution also will make your antimicrobial activity determination process becomes more difficult and tends to give unprecise result

My dear friend, you can not ask a question like this. You must use all the solvents you have mentioned in addition to acetone  and chloroform and may be diethyl ether. It is because you do not know in which extract you will get the anti microbial compounds.

Hello Sony Mac,

I am agree with @Jai Ghosh, First of all you have to try all solvents separately or fractional extraction system. Most of reported paper suggest Methanol is a good solvent for extraction; because chemical studies of methanolic extract always shows maximum components from extract compair to other solvents.

Hope so this information may helpful for your research.

Have a good time.

Quality of plant extract depends on plant material, choice. However, the decision on the methods of extraction to be used could also be dependent on the amount of certain phytochemicals required and the solubility of the extracts in solvents after extraction.

Generally plant extraction for bio-activity aspects methanol/ ethanol is used but as suggested in previous comments you should extract using solvents ranging from non-polar to polar and test for their activities.

My intuition would be to try general-mechanical means for extracting the raw exudate.  This could be done by French press, ultra-sonication or other rigorous method.  I WOULD SHY AWAY FROM ORGANIC SOLVENTS, at least initially.  The compounds your after are naturally occurring in water and the effect of organic solvents on them is unpredictable,  Of course, if you wish, ethanol or methanol are good choices for polar protic solvents with minimal reactivity.  At any point, you could do a filter disc susceptibility test to see if there is activity.  Naturally, any solvent would have to be removed (vacuum dry under cold temp?

Good luck!

Dear Sony,

Find in attached a paper on: Extraction methods and bioautography for evaluation of medicinal plant antimicrobial activity

A. Nostro, M.P. GermanoÁ , V. D'Angelo, A. Marino and M.A. Cannatelli

Letters in Applied Microbiology 2000, 30, 379ÿ384

In this paper you'll find:

Two methods of extraction were employed. In method A,

a known amount of powdered drug (50  g) was sequentially

extracted at room temperature with petroleum ether (30, 50 

C) (1), dichloromethane (2), dichloromethane  :  methanol (9  

:  1) (3) and methanol (4).The four extracts were concentrated

to dryness using a rotary evaporator at 40  C.  In method B,a

known amount of powdered drug (50  g) was extracted as

reported by Al-Sarraj et al. (1985).The drug was suspended

in enough distilledwater to forma homogeneous suspension.

The mixture was adjusted to pH 20 withHCl (1N) and then

incubated at 37  C for 30  min in a shaking water-bath. The

mixture was then neutralized with NaOH(1N) to pH 70, ¢l-

tered, extracted with diethyl ether and concentrated to dry-

ness (1). The remaining aqueous extract (2) was lyophilized.

All solventswere purchased fromMerck (Milan, Italy).

Best wishes

Plants produce a diverse array of secondary metabolites, many of which have antimicrobial activity.

Some of this compounds are constitutive, existing in healthy plants in their biologically active forms. Others such as cyanogenic glycosides and glucosinolates, occur as inactive precursors and are activated in response to tissue damage or pathogen attack.

Dear Sony,

Extraction Methods Advice abounds for the amateur herbalist on how to prepare healing compounds from plants and herbs. Water is almost universally the solvent used to extract activity. At home, dried plants can be ingested as teas (plants steeped in hot water) or, rarely, tinctures (plants in alcoholic solutions) or inhaled via steam from boiling suspensions of the parts. Dried plant parts can be added to oils or petroleum jelly and applied externally. Poultices can also be made from concentrated teas or tinctures (30, 224).

Scientific analysis of plant components follows a logical pathway. Plants are collected either randomly or by following leads supplied by local healers in geographical areas where the plants are found (135). Initial screenings of plants for possible antimicrobial activities typically begin by using crude aqueous or alcohol extractions and can be followed by various organic extraction methods. Since nearly all of the identified components from plants active against microorganisms are aromatic or saturated organic compounds, they are most often obtained through initial ethanol or methanol extraction. In fact, many studies avoid the use of aqueous fractionation altogether. The exceptional water-soluble compounds, such as polysaccharides (e.g., starch) and polypeptides, including fabatin (253) and various lectins, are commonly more effective as inhibitors of pathogen (usually virus) adsorption and would not be identified in the screening techniques commonly used. Occasionally tannins and terpenoids will be found in the aqueous phase, but they are more often obtained by treatment with less polar solvents. Table3 lists examples of extraction solvents and the resultant active fractions reported in recent studies. Compounds which, according to the literature, partition exclusively in particular solvents are indicated in boldface type in the table.

This is find in:

Plant Products as Antimicrobial Agents

Marjorie Murphy Cowan* 

Clin. Microbiol. Rev. October 1999 vol. 12 no. 4 564-582

1 October 1999

Best wishes

Generally Solvents - Methanol, Ethanol etc.. have pharmacological activities. If you prefer those solvents, surely it will show good response. But that report is not only due to phytochemicals present in plant, it's also because of solvents used in extraction of plant material.

Better to go with Decoction Method using water (Don't use high temperature-it may lead to loss of certain bioactive compounds) - Use freshly prepared decoction regularly while testing for antimicrobial susceptibility...

[Note - Check for Phytochemicals - With plant material powder sample and also With Decoction extract prepared]

Try acetone, as it afford extraction of both non-polar and polar chemical constituents. Also, acetone have been shown to be non-toxic towards test organisms.

isopropyl alcohol ( the longer the chain the better for antimicrobial activity)

Depends upon the composition you want to isolate. However, may be the plant biology book by Harbor can give you right direction.