Abstract
Morinda citrifolia (Noni), a plant that has been used in folk remedies for over 2000 years, has recently gained increased interest from the scientific professionals. The roots of Noni plants were used by Polynesians to produce yellow dye, but more importantly, they contain medicinally active components, namely anthraquinones. The compounds show several therapeutic effects, which include anti-bacterial, anti-viral, and anti-cancer activities as well as analgesic effects, which make them useful in several medical applications.
Conventionally, the compounds are extracted with ethanol, followed by evaporation to separate solvent from the product but this could leave residual solvents in the product.
In this study, subcritical water was used as a benign alternative solvent for extraction of the dried Noni roots. The effect of various operating conditions such as water temperatures (383 K, 443 K and 493 K), pressures (3MPa and 7MPa), and flow rates (2, 4, and 6 ml min-1) on extraction yield and extraction rate were determined. At the operating temperature of 493 K, the extraction yield was the highest and was found to be about 80% of ethanol extracted. Pressure had no significant effect on the results for the range of temperatures studied. The flow rate of 6 ml min-1 resulted in the highest extraction rate, but the extraction efficiency, as measured by the amount of anthraquinones extracted per unit volume of water was lower than that of 4 ml min-1. The results of anthraquinones solubilities in subcritical water at various temperatures and the extraction mechanism will be discussed.
