It seems you lack some basic understanding and terminologies regarding the extraction of compounds and analysis. Plant extract is a complex mixture of several group of compounds and to use that extract in some sort of drug discovery, you need to identify and characterize the group or molecule of your interest. Regarding methanol, it is toxic to human because it is volatile and fumes can harm while inhaling, but it is a good solvent. You don't have to give any justification for that since it is a commonly used solvent in labs.

Methanol can be completely removed at some stage through different techniques such as rotor- vaporization then dissolve your extracts in non toxic solvents like water. Check what others have done on similar studies:

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Thank you sir

It seems you lack some basic understanding and terminologies regarding the extraction of compounds and analysis. Plant extract is a complex mixture of several group of compounds and to use that extract in some sort of drug discovery, you need to identify and characterize the group or molecule of your interest. Regarding methanol, it is toxic to human because it is volatile and fumes can harm while inhaling, but it is a good solvent. You don't have to give any justification for that since it is a commonly used solvent in labs.

Extraction and testing of natural products is just the first step in your study. It is an estimation and preliminary work even it contain trace of solvent (after evaporation). To continue you work for drug discovery, you have to synthesize the most active molecules and test them again. Drug discovery is an amazing field which need patience.