Folin ciocalteu reagent

Total phenolic content of the extractives was measured by using Folin-Ciocalteu reagent (Merck, Germany) as an oxidizing agent and gallic acid (Merck, Germany) as a standard [24 ]. In this assay, 0.5 ml of the extract (2 mg/ml) in water was mixed with 2.5 ml of Folin-Ciocalteu reagent (10 times diluted with water) and 2 ml of 7.5 % w/v sodium carbonate (Merck, Germany) solution and incubated for 20 min in room temperature. The absorbance was measured at 760 nm using a UV-visible spectrophotometer (UV-1800 UV–VIS Spectrophotometer, Shimadzu, Japan). Total phenolic content was quantified by calibration curve obtained from measuring the known concentrations of gallic acid (0–100 μg/ml). It was expressed as mg of GAE (gallic acid equivalent)/g of the dried extract.

Total polyphenol content (TPC) was determined using the Folin–Ciocalteu reagent at 0.25 N (Merck, Darmstadt, Germany) and 20% Na2CO3 (Spectrum, NB, Canada). A calibration curve was prepared from 5 to 35 mg/L gallic acid (Merck, Darmstadt, Germany), with R² of 0.98.
In total, 0.9 mL of methanolic extract of the fruit was taken and mixed with 0.15 mL of Na₂CO₃, 0.30 mL of Folin–Ciocalteu reagent, and 0.90 mL of ultrapure water. The mixture was kept for 90 min in the dark and then taken to a UV spectrophotometer, Thermo Fisher brand, Genesys 150 model (Waltham, MA, USA), and absorbance readings were made at 750 nm. The results were expressed as mg/gallic acid equivalent (GAE) per 100 g of sample on a dry basis [78 (link)].

For total polyphenol index (TPI) determination, Folin–Ciocalteu reagent was purchased from Merck (Darmstadt, Germany) and anhydrous sodium carbonate was supplied by Panreac (Barcelona, Spain).
Folin–Ciocalteu reagent, anhydrous sodium carbonate, and gallic acid, for total polyphenol index (TPI) determination, were purchased from Merck (Darmstadt, Germany), Panreac (Barcelona, Spain) and Sigma-Aldrich (Saint Louis, MO, USA), respectively.
For organic acid analyses, ethylenediaminetetraacetic acid (EDTA), 2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol (Bis-Tris), and trifluoroacetic acid (TFA) were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Standards for calibration were supplied by Panreac (Barcelona, Spain), Sigma-Aldrich (Saint Louis, MO, USA) and Scharlab (Barcelona, Spain).
UHPLC grade acetonitrile from Panreac (Barcelona, Spain), acetic acid from Merck (Darmstadt Germany) were used to prepare the UHPLC phases. Standards for calibration were purchased from Sigma-Aldrich (Saint Louis, MO, USA). Deionized water from EMD Millipore (Bedford, MA, USA) was used to prepare the chromatography phases, reagents and standards for calibration.