Valorisation of plant seed as natural bioactive compounds by various extraction methods: A review

The extraction of essential oil from plant seeds has a great economic potential for applications in the pharmaceutical, cosmeceutical and food industries. Oilseeds contain various phytochemical compounds such as polyphenols, fatty acids and flavonoids, which are essential for the health maintenance and prevention of disease. Seeds are generally regarded as waste in the agricultural industry; hence the maximum usage of seeds will greatly reduce the problem of final disposal. This review describes conventional; Soxhlet, Hydrodistillation, Microwave-Assisted and modern; Supercritical Carbon Dioxide, Subcritical water, High Hydrostatic Pressure, Ultrasound-assisted extraction methods with a focus on parameters that affect each technique. Comparisons of its oil yield and the recovery of seeds from different plants are considered to assess the efficiency of the method of selection. Parameters such as time, temperature, pressure and particle size which influence the production of oil yield and its quality are also highlighted. Conventional extraction methods are usually use polar or non-polar solvents, with lower temperature and requires longer time to produce high yield. The application of high microwave power can also obtain high yields in short period of time. While, modern method uses pressure or elevated temperature with increasing flow rate can increase the oil yield in shorter time. Therefore, the selection of the most effective methods of extracting oil from plant seeds is important to preserve the quality and achieving maximum effect.