The laboratory of Pharmacognosy of the University of Athens is involved in the extraction and analysis of natural products since decades. So far, the extractions method followed typical procedures like e.g. maceration for several days in solvents of different polarity. Despite its simple execution, this method is generally time and solvent-consuming.
Since a couple a years the use of ultrasound takes a greater place in the phytochemistry because of its simplicity of implementation and its efficiency. Its principle applied to the extraction of natural products could avoid us loosing time or a too big consumption of solvents and could increase the extraction yield.
We used an Elma S100 H ultrasound bath (Elmasonic, P=500W, f=50-60Hz). For tall the ultrasonic-maceration realized in the lab, the average extraction-time was around 1h instead of 1 day! More interesting, the consumption of solvent was lightly decreased and the yield of the extraction was increased of about 10% in best cases.
Now in our laboratory, most of the extraction by maceration are realized this way. Despite these excellent results, questions remain unanswered: What about those sensitive to heating? Could this method be applied to all the categories of natural compounds?
Concerning the extraction of essential oil, we used a Multi-mode Milestone START E micro-waves to perform hydrodistillation. A trial has been realized on 300g Corydothymus capitatus. The yield was the same than the one described on literature but the time was decreased from 3h to 15 min! GC-MS analysis are on going to determine the quality of the extraction. Engaged in the valorization of olive leaves products and especially their main active metabolite, oleuropein, we realized its microwave assisted extraction using a mix EtOH/H2O (8/2) with an irradiation of 200W during 10 min. Oleuropein was obtained with a yield of 34%.
Our laboratory is also involved in the synthesis of natural compounds. In this perspective, the quest for better yields and easily replicable methods on pilot scale is constant and the use of Micro-waves technology is an alternative first choice.
We used a Single-Mode CEM Discover Microwave to optimize the last step of the synthesis of a powerful GSK-3β inhibitor.
The Milestone START E was used to realize simple reactions like Friedel-Craft or palladium-catalyzed reactions like Suzuki or Sonogashira reactions like described below.
According importance to all eco-friendly and modern technologies, our use of ultrasound and microwaves becomes more and more important and starts to change our way of working. They allow us to perform faster and cheaper extraction, to optimize the yield of our synthesis and to propose methods potentially applicable on pilot-scale. Given the growing impact of sonochemistry, we’ll develop soon chemical synthesis integrating this technology.
