Artemisinin content of sc-C0₂ derived extracts from Artemisia annua / Surisha Padayatchi.

Abstract

One of the principal research themes of the supercritical fluid research group within the Centre of Separation Science and Technology (SST) at the North-West University (Potchefstroom Campus) is botanical extraction. The group produces botanical extracts from locally cultivated plants which contain substances (essential oils, natural waxes) relevant to the food, flavour, pharmaceutical, medical and cosmetic industries while utilising the advantages of sc-C& extraction over traditional steam distillation and solvent e~traction.'.~ In this study, which represents a contribution to a series of botanical extractions performed within the core programme outlined above, sc-COz extraction of artemisinin from Artemisia annua (or wormwood) was investigated. The active component is a potential cure against ma~aria.It~ w ould have been desirable to extract it with no solvent residues left in the final product to prevent side-effects on taking the medicine. The extraction by clean technology, using environmentally friendly sc-C&, could be relevant as it offers an affordable alternative for synthetically prepared medicines in the marketplace. The manipulation of the conditions (temperature and pressure, or density) for sc-C02 extraction could facilitate more selective isolation of the active component and thereby enhance the medicinal value of wormwood. The unique solvent strength and mass transport characteristics of sc-C02 offer the possibility of obtaining better results than with other solvent based extraction methods. The specific goals with the project were to extract an active component or ingredient (artemisinin) from the leaves of wormwood with sc-COz on laboratory scale by using an advanced benchtop supercritical fluid extractor and other available laboratory infrastructure; to compare the results of sc-COz extraction with those of classical extraction methods, such as solid-liquid extraction, to ascertain the advantages and disadvantages of different extraction methods; to identify and implement suitable analytical techniques (HPLC andlor GC) with which artemisinin containing extracts can be analysed qualitatively and quantitatively; to identify process parameters and to vary these according to a statistical design using a suitable software programme (Statistica for windows@) to establish optimum conditions for the extraction of the target component; to process the extraction data mathematically and/or graphically in such ways as to reveal the principal features of the extraction process, to facilitate modelling of the process and to enable calculation of mechanism directive activation parameters; to complement comparable studies performed in the research group. In addition to these specific goals, the project also served the purpose to contribute to a lesser extent to the following relevant issues: The essential oils, natural waxes and other chemical components derived from plants are low-volume high-value products and therefore have significant commercial value.' The importance of clean technology for "green" or sustainable chemistry is increasingly emphasised.6 sc-C02 is an environmentally friendly solvent with which solvent-free extracts can be derived. There are academic interest in and financial support for the development of knowledge about indigenous plants.7 The suitability of sc-COz for the isolation of plant components derived by traditional healers for centuries can help to better understand the beneficial effects of plant medicines. The relevance of supercritical fluid based processes for daily life creates science awareness and renders the research done in this investigation suitable for the popularisation and promotion of chemistry since the replacement of natural products in ordinary household products (beer, shampoo) captures the attention and imagination of the public. Finally, this investigation can help to convince industry to apply the technology despite of the negative perceptions about extreme conditions and the high capital investment needed to put up the required infrastructure.