Extraction of anti-cancer damnacanthal from roots of Morinda citrifolia by subcritical water

Abstract

A technique of solvent-free extraction of anti-cancer damnacanthal, from roots of Morinda citrifolia was proposed. The technique utilizes subcritical water, or sometimes called pressurize hot water (PHW) as extraction medium. A series of extraction experiments were carried out at different conditions, i.e., temperatures of 150, 170, 200, and 220 ํC and flow rates of 2, 3, 4, and 5 ml/min, while the pressure remained fixed at 4 MPa. The quantitative analysis of damnacanthal was performed with reverse phase-high performance liquid chromatography (RP-HPLC). Prior to the analysis, a sample preparation step was required to concentrate the damnacanthal product. This was achieved by evaporating off water from the extract under vacuum, and the distilled water was added to the dried extract. This resulted in two parts, the aqueous solution and the precipitate. The aqueous solution was analyzed for the amount of damnacanthal by RP-HPLC, while the precipitate was re-dissolved into dimethylsulfoxide (DMSO), and then analyzed with RP-HPLC. The total amount of damnacanthal extracted was the sum of the amounts in the two fractions. The results of the study revealed that the extraction yield increased as the temperature increased. However, at the temperature of 200 and 220 ํC, decomposition of damnacanthal occurred. In addition to the effect of temperatures, extractions were conducted at various flow rates and the data were fitted with mathematic models to determine the extraction mechanism. The results suggested that the overall extraction mechanism was influenced by solute partitioning equilibrium and external mass transfer through liquid film, although the desorption model could describe the subcritical extraction behavior of Morinda citrifolia reasonably at high flow rates.