You can do a better screening if you select solvents in the following order of polarity:

Petroleum ether/ hexane- ethanol- water

Although you will get three extracts in each case, but your screening purpose will be fulfilled.

Further you will get an idea of the phytoconstituents present in each fraction and their phytochemical nature too.

Regards

Thank you sir, actually we want test toxic studies of few medicinal plants in order to that we want do preliminary screening with few grams of plant material so that we can get the potent plant from that remaining can be omitted so for that i need an appropriate solvent for extraction whether to take ethanol or ethanol :water or decotion

You can do a better screening if you select solvents in the following order of polarity:

Petroleum ether/ hexane- ethanol- water

Although you will get three extracts in each case, but your screening purpose will be fulfilled.

Further you will get an idea of the phytoconstituents present in each fraction and their phytochemical nature too.

Regards

@ Kattamanchi Gnananath,

If I was doing such work, I would like to follow methodology suggested by Alok Nahata.

We have spent much time in adressing this question. One paper cited more than 500 times addressed this question by investigating several different aspects. (Eloff, JN 1988 Which extractant should be used for the screening and isolation of antimicrobial components from plants? Journal of Ethnopharmacology 60, 1-8) Aspects investgated were the number of different compounds extracted, quantity extracted, rate of extraction, ease of removal of the solvent, safety of the solvent to humans and to microorganisms. Acetone was by far the best extractant this is mainly because from commonly available solvents it is the only one that mixes with water and with hexane. Becasue like dissolves like it extracts the most widely different polarity compounds.

These results were confirmed when the chemical composition and antimicrobial activity of 11 different extracts with a wide ranege of polarity were investigated (KOTZE M and ELOFF J N 2002 Extraction of antibacterial compounds from Combretum microphyllum (Combretaceae). South African Journal of Botany 68, 62-67 as well as ELOFF JN, FAMAKIN JO and KATERERE DRP [2005] Combretum woodii (Combretaceae) leaf extracts have high activity against Gram-negative and Gram-positive bacteria. African Journal of Biotechnology 4, 1161-1166)

A very important result in all these papers were that water extracts had very low or no antimicrobial activity.