I fully agree with Mr Richard Bruce suggestion to you. 50% MeOH will cover almost polar metabolites. You can use Ethanol or Methanol, whichever is easy available with you. Generally, people are using methanol due to its easy availability. Ethanol may be restricted in certain regions.
Ethanol, methanol and water are good for extracting polar metabolites. Extracting with 50% MeOH is a good start as it will extract compounds that are not extractable in water alone, i.e. slightly less polar metabolites.
I fully agree with Mr Richard Bruce suggestion to you. 50% MeOH will cover almost polar metabolites. You can use Ethanol or Methanol, whichever is easy available with you. Generally, people are using methanol due to its easy availability. Ethanol may be restricted in certain regions.