Investigation of extraction conditions for Oroxylum indicum root using ultrasound-assisted extraction and statistical design of experiments

Oroxylum indicum (L. Kurz) is a traditional medicinal herb found in Thailand. Various parts of this plant have been used in traditional Thai medicine and folk practices. Oroxylum indicum roots are consumed to enhance digestion, stimulate appetite, treat diarrhea and dysentery, and alleviate intermittent fever. Studies have been conducted to evaluate the preliminary phytochemical screening and the active compounds present in O. indicum. Three-variable factors were examined to determine the optimal conditions for extracting its roots using ultrasonic-assisted extraction: solvent concentration, extraction time, and material-to-solvent ratio. The study employed a Box-Behnken Design (BBD) statistical method to design 17 experimental runs. The results indicated the optimal condition for achieving the highest extraction yield of 15.49%. Regarding the total phenolic and flavonoid content, the maximum amounts obtained were 76.63 mg gallic acid equivalents per gram extract and 24.85 mg quercetin equivalents per gram extract, respectively. The major active compounds identified in O. indicum root were baicalin, baicalein, chrysin, and oroxylin A, with their highest contents being 18.84, 41.69, 9.22, and 23.64 mg/g extract, respectively, depending on the different conditions. Therefore, it is crucial to consider optimal extraction conditions to maximize compound yields. The application of BBD and numerical optimization in experimental design serves as a robust and systematic approach to optimizing extraction processes. This approach not only reduces the need for extensive trial-and-error experimentation but also saves time and resources.