Enzymatic and ultrasound-assisted extraction of bioactive triterpenoids from Centella asiatica

Centella asiatica (L.) Urban, commonly known as gotu kola or bua-bok in Thai, is a medicinal herb valued for its rich content of pharmacologically active triterpenoids, notably asiaticoside, madecassoside, asiatic acid, and madecassic acid. These compounds contribute to a range of therapeutic effects, including wound healing, antioxidant, anti-inflammatory, antibacterial, and neuroprotective activities. However, conventional extraction methods such as maceration and Soxhlet extraction are often constrained by long processing times, high solvent usage, and low extraction efficiency. To address these limitations, this study investigates an integrated green extraction strategy that combines enzymatic pretreatment with ultrasound-assisted extraction (UAE) for the efficient recovery of triterpenoids from C. asiatica. Enzymatic hydrolysis using cellulase was employed to degrade plant cell wall structures, thereby enhancing the accessibility of intracellular compounds. This was followed by UAE, which utilizes acoustic cavitation to facilitate the rupture of plant tissues and improve mass transfer. The optimized extraction conditions yielded notably high concentrations of triterpenoids. Specifically, asiatic acid and madecassic acid achieved 19.72% (w/w) and 16.48% (w/w) respectively using a sample-to-solvent ratio of 1:30 (DI water), enzymatic incubation at 45°C for 30 min, followed by UAE at 45°C for 20 minutes with a water:EtOAc (1:1) solvent system. The extracted compounds were confirmed and quantified using thin-layer chromatography (TLC), proton nuclear magnetic resonance (1H NMR). This study highlights a cost-effective, environmentally friendly, and scalable approach for enhancing the yield and purity of bioactive triterpenoids from C. asiatica, offering promising applications in the pharmaceutical, nutraceutical, and cosmetic industries.