Cavitation-driven extraction: how ultrasound-induced acoustic cavitation maximizes bioactive compound recovery from S. costus roots.

Saussurea costus (Falc.) Lipsch., an endangered Indo-Himalayan medicinal plant, is highly valued for its roots enriched with polyphenols and sesquiterpenes of therapeutic relevance. In this study, ultrasonic-assisted extraction (UAE) was evaluated as a sustainable and efficient alternative to conventional techniques for recovering bioactive metabolites from S. costus roots. Process optimization was carried out using response surface methodology (Box-Behnken design) with aqueous ethanol (50:50, v/v) as the extraction medium. The cavitation-driven process significantly (p ≤ 0.05) improved recovery efficiency, yielding 29.98 ± 0.23 % extract compared to Soxhlet (26.53 %) and maceration (24.67 %). UAE extracts exhibited elevated levels of phenolics (66.27 ± 0.02 mg GAE/g) and flavonoids (73.33 ± 1.23 mg QE/100 g), alongside superior antioxidant capacity (52.29 ± 2.20 % DPPH inhibition; 197.56 ± 1.10 µmol TEAC/g FRAP). Mechanistic insights suggest that acoustic cavitation enhances mass transfer and disrupts cellular structures, thereby facilitating the release of both polar and non-polar phytoconstituents more effectively than thermal approaches. HPLC profiling further confirmed selective enrichment of key phenolics, including gallic acid, chlorogenic acid, and naringenin. Collectively, these findings establish UAE as a scalable, eco-friendly, and high-performance extraction strategy, underscoring its potential for producing S. costus extracts with significant nutraceutical and pharmaceutical applications.