OPTIMISATION OF EXTRACTION OF THYMOL FROM PLECTRANTHUS AMBOINICUS LEAVES USING RESPONSE SURFACE METHODOLOGY

Plectranthus amboinicus (PA) is one of the herbal plants that traditionally used to cure asthma, coughs and diseases affected by virus and bacteria. The objectives of this study were to extract essential oil from the leaves of this plant and optimise the extraction parameters using the Response Surface Methodology (RSM). The PA leaves were dried using a convection air drying method and followed by extraction using a Soxhlet method. Design Expert 6.0.8 was used to design the experiments based on the Box-Behnken Design with three parameters to control, viz. types of solvents, ratio of solid to solvent and extraction time. The types of solvents used were ethanol (95%), n-hexane (85%) and diethyl ether (99.5%). While for the ratio of solid to solvent were 1:30, 1:35 and 1:40. The extraction time was set in between 4 to 6 hours. The extracts obtained from different Soxhlet extraction parameters were concentrated to 5 ml using a rotary evaporator and analysed using a Gas Chromatography (GC) with a flame ionization detector. It was found that higher concentration of thymol was observed in the oil extracted using ethanol. The optimum extraction conditions were 6 hours with ratio of solid to solvent of 1:30.