Qualitative and Quantitative Analyses of Gallic Acid and Methyl Gallate in Guyinye Residue Extracts and Turkish Gall Cream by High-Performance Thin-Layer Chromatography

The aim of this work was to establish qualitative and quantitative methods for studying Guyinye residue extracts and Turkish gall (TG) cream. This study involved qualitative and quantitative analyses of gallic acid and methyl gallate and determined their preliminary antioxidant activity by high-performance thin-layer chromatography (HPTLC) and thin-layer chromatography-1,1-diphenyl-2-trinitrobenzene hydrazine (TLC-DPPH) in Guyinye residue extracts and TG cream. The thin-layer plate was a polyamide film and glacial acetic acid, methanol, ethyl acetate, and formic acid (10:6:2:1, volume ratio) were used as the developing agent. The scanning wavelength was 280 nm. Results showed that the R-F values of gallic acid and methyl gallate were 0.57 +/- 0.05 and 0.72 +/- 0.05, respectively, and their linearity ranges were 0.001-0.005 and 0.00025-0.00125 mg with correlation coefficients of 0.9990 and 0.9994, respectively, which indicated a good linear relationship. The detection limits of gallic acid and methyl gallate were 3 and 75 ng, respectively, and their quantification limits were 10 and 250 ng, respectively. The average recovery was 98.59% and 98.33%, and the relative standard deviation (RSD) was 2.49% and 3.55%, respectively. Gallic acid was more remarkable than methyl gallate in antioxidant activity. Thus, HPTLC combined with TLC-DPPH, which can rapidly and accurately determine gallic acid and methyl gallate in Guyinye residue extracts and TG cream, is a simple, accurate, and rapid qualitative and quantitative method.