Extraction of Bioactive Components from Centella Asiatica Using Subcritical Water

Centella asiatica is a tropical medicinal plant with a long history of therapeutic uses, dermal disorders, venous insufficiency and microangiopathy. The substances of therapeutic interest are the saponin-containing triterpene acids and their sugar esters. Two bioactive components, asiatic acid and asiaticoside, were extracted from Centella asiatica using subcritical water as an extraction solvent. Extraction yields of asiatic acid and asiaticoside were measured using high-performance liquid chromatography (HPLC) at temperatures from 100 to 250 C and pressures from 10 to 40 MPa. As temperature or pressure increased, the extraction yield of asiatic acid and asiaticoside increased. At optimal extraction condition of 40 MPa and 250 C, the extraction yield of asiatic acid was 7.84 mg/g and the extraction yield of asiaticoside was 10.0 mg/g. Extracted asiatic acid and asiaticoside could be collected from water as particles with a simple filtering process. Dynamic light scattering (DLS) was used to characterize particle size. Particles containing asiatic acid were larger than particles containing asiaticoside, thus asiatic acid and asiaticoside can be separated each other using two different size of filters. The extraction yields of asiatic acid and asiaticoside using subcritical water at 40 MPa and 250 C were higher than extraction yields using conventional liquid solvent extraction with ethanol at room temperature while the subcritical water extraction yields were lower than extraction yields with ethanol at its boiling point. INTRODUCTION Subcritical water extraction is a technology that modifies the physical properties of water by increasing the temperature up to 374C and by keeping the pressure high enough to maintain the water in the liquid state to improve its extraction ability. Subcritical water can be an