Microwave-assisted extraction of the gallic acid biomarker from Acacia arabica bark followed by HPLC analysis

An efficient and fast microwave-assisted extraction (MAE) technique was developed for extracting gallic acid as an indicative biomarker for the quality control of Acacia arabica bark. The MAE technique was optimized and compared with other conventional extraction techniques. The optimal conditions of MAE were 20% methanol as solvent, solid/liquid ratio 1:40 (g/mL), irradiation power 20% and two extraction cycles, 5 min each. The proposed extraction technique produced a maximum yield of 10.59 (mg/g) gallic acid in 10 min, which was 1.03 and 1.15 times more efficient than 6 h of heat reflux and 24 h of maceration extraction, respectively. This high yield, along with saving of time, energy, and solvent would position MAE as a valuable and cost-effective technology suitable for today's highly competitive industries, with growing demand for increased productivity, improved efficiency, and reduced cycle time. Moreover, a new high-performance liquid chromatography method was developed and validated for the determination of gallic acid in Acacia arabica bark extract. The method was found to be rapid, sensitive, accurate, precise, and robust. The method showed good linearity over concentration range 1-100 (µg/mL) with LOD 16.08 (ng/mL) and LOQ 48.73 (ng/mL). The average recovery obtained using standard addition technique was 100.36% with a low value of RSD% (1.19%) indicating the accuracy of the proposed method for determination of gallic acid in Acacia arabica bark extract.