I am using the Folin-Ciocalteu method for analysis of total phenolic content in ripe strawberries. I've read several protocol that suggest a methanol/H2O/formic acid (80:19:1) extraction solution. Can someone explain the use of formic acid here, as opposed to other acids? How is this reagent acting in helping to develop color in during the FCM reaction?
And https://www.researchgate.net/publication/266392512_Effects_of_solvent_extraction_system_on_concentration_and_antioxidant_activity_of_strawberry_phenolics
Some of phenolic compounds are bound to macromolecules such as structural proteins, cellulose and pectin through covalent bonds found in the cell wall matrix, forming insoluble-bound phenolics. The addition of acids like hydrochloric acid and organic acids to hydromethanolic solvents aims generally to liberate these bound phenolic compounds during extraction.
As you know, the reduction of folin ciocalteu reagent by phenolics can be better occured at alkaline pH not acidic condition.
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