2018/11/15 · Each filtrate was brought to 25 mL with MeOH:HCOOH (99:1 vol:vol) into a volumetric flask. The diluted extract was then filtered again with a 0.45 µm cellulose acetate syringe filter (Whatman) into an HPLC vial and then stored at +4 C at dark before injection 2.4.