Green Extraction of Rosemary (Rosmarinus officinalis L.) with Ultrasonic Assistance Essential Oil: A Comparison of Hydro and Soxhlet Distillation Techniques with RSM Optimization

The rosemary essential oil, REO (Rosmarinus officinalis L.) is a natural plant derivative widely used in food and pharma industries. Long processing time and huge requirement of solvent are drawbacks in the traditional methods of extractions such as Soxhlet extraction (SE) and hydrodistillation (HD). Ultrasonic pretreatment has become a viable process to come up with these limitations by rupturing plant cell walls and enhancing penetration of solvent. The REO extraction was performed in four methods including Traditional hydrodistillation with Clevenger apparatus, Ultrasonic Pretreatment followed by HD (UPHD), Traditional SE and Ultrasonic pretreatment followed by SE (UPSE). Response Surface Methodology (RSM) approach was adopted using a central composite design to optimize the parameters for Soxhlet experimental runs, with ultrasonic bath at (20-30°C) and treatment time (5-15 min) throughout nine experimental runs. The resulting quadratic model demonstrated robust performance (R2 = 0.967, adjusted R2 = 0.912). UPSE produced 1.70% oil in 2.53 hours at ideal pretreatment conditions of 25°C and 10 mins, with 22% increase over traditional SE (1.39%, 6 hours). UPHD gave 1.89-1.91% in 55-60 minutes, whereas regular HD gave 1.41-1.46% during 90-95 mins. Overall, Ultrasonic- assisted extraction is more effective than traditional method of extraction, but using higher intensity of ultrasonic can damage and breakdown important oil compounds like monoterpenes and reduce the benefits. Calculated ultrasonic pretreatment improves the extraction of REO, providing a low-footprint, Sustainable method with effective outcomes for large scale manufacturing of natural preservatives and bioactive compounds.