Ultrasound Assisted Hydrotropic Extraction: A Greener Approach for the Isolation of Geraniol from the Leaves of Cymbopogon martinii

Geraniol, a prime constituent in the leaves of Cymbopogon martinii, has a varied range of biological activities and applications. For the selective isolation of geraniol, a newer concept of combining hydrotropic extraction with ultrasound was adopted to reduce the time of extraction and hydrotrope requirement while maintaining the quality of the product. Sodium cumene sulfonate was selected as a suitable hydrotrope among sodium cumene sulfonate, sodium salicylate, sodium salt of para-toluene sulfonic acid, and resorcinol using the solubilization study. The screening of extraction parameters, viz., ultrasound amplitude, cycle time, volume of hydrotropic solution, hydrotropic concentration, ultrasonic power, and sonication time, was carried out using the Taguchi method. Optimization of process parameters was performed using central composite response surface design. A 1.9012% (w/w) yield of geraniol was obtained under optimized conditions (65% ultrasound amplitude, 65 mL volume of 1 M aqueous solution of sodium cumene sulfonate, 60 W ultrasound power, 70% cycle time, and 16 min of sonication time). A microscopic study was also performed to understand the extraction mechanism. Ultrasound assisted hydrotropic extraction turned out to be a superior sustainable alternative compared to the hydrotropic extraction because of the shortening of extraction time and reduction in hydrotrope concentration.