Thin-layer chromatography for determination of phenolic compound profile and antioxidant activity of Thai honey

Abstract

In this study, a small-scale method using thin-layer chromatography (TLC) was developed to determine profile and antioxidant activity value of Thai honey samples obtained from different flora sources. Prior to TLC analysis, the samples were prepared by solvent extraction with dichloromethane. Using 2, 2-diphenyl-1-picrylhydrazy radical (DPPH•) reacted with the samples extract prior to TLC spot and color detection with imageJ, half-maximal inhibitory concentration (IC50) values of seven honey samples was obtained in a range of 9 to 22 mg/mL in comparison with IC50 values of 0.13 mg/mL for L-ascorbic acid (LA), along with limit of detection (LOD) and limit of quantitation (LOQ) for antioxidant activity of 0.010 and 0.030 mg/mL, respectively, using a linear calibration plot between %inhibition and concentration of LA. Note that TLC-DPPH• and UV-Vis methods for %inhibition determination give linear correlations of y = 2.2073x - 76.864 with R2 of 0.98 for LA and y = 4.0683x - 135.22 with R2 of 0.95 for Longan honey sample where x and y are the %inhibition obtained from UV-Vis and TLC-DPPH•, respectively. For TLC determination of total phenolic compounds using Folin–Ciocâlteu (FCR) reagent reacted with gallic acid (GA) or samples extract prior to TLC spot and color detection with imageJ, a linear calibration plot of y = 0.2024x + 4.2946 with R2 of 0.96 for GA were obtained between the color value (y) and GA concentration (x), along with LOD and LOQ for total phenolic compounds of 0.016 and 0.049 mg/mL, respectively. In addition, the total phenolic compounds of seven honey samples were found in a range of 1 to 14 mg GA/g extract.