Microwave-assisted extraction of gallic acid in leaves of Eucalyptus x hybrida Maiden and its quantitative determination by HPTLC

High yield and fast extraction performance ability with less solvent consumption and protection offered to thermo labile constituents are some of the attractive features of this new promising microwave-assisted extraction (MAE) technique. Therefore, MAE of gallic acid in the leaves of Eucalyptus x hybrida Maiden has been carried out and precise HPTLC method was developed for quantitative analysis of gallic acid in the leaf extracts. A range of non-polar to polar solvents were used for the MAE. A mixture of methanol: water (60:40, v/v; 20 mL) as solvent and microwave power (900 W), irradiation time of (120 s) were found to be most favorable for maximum extraction of gallic acid from the leaves. HPTLC experiments were performed on aluminum sheets pre-coated with silica gel 60 F254. For achieving good separation, mobile phase consisting of chloroform: ethyl acetate: formic acid (50:50:3, v/v/v) was used. The densitometric estimation of gallic acid was carried out at λ 288 nm in remission/absorption mode. Method was validated in terms of linearity, specificity, precision, accuracy and recovery. Maximum yield 27.3% of extract was found with methanol: water (60:40, v/v) mixture, while lowest yield 2.36% was found with nhexane when used as solvent. 100 g leaves of E. hybrida contained 114.26 μg of gallic acid on dry weight basis, when extracted with mixture (methanol: water). The proposed method would be useful for rapid quantitative determination of gallic acid in E. hybrida and its related preparations for quality assessment.