My pharmacognosy presentation on Microwave Assisted Extraction

1. Microwave-assisted
Extraction (MAE)
Presented by: Naraino Majie Nabiilah
Date: 28th August 2014

2. Table of Content
• Introduction
• Microwave theory
• Extraction principle
• Instruments
– Closed vessel
– Open vessel
• Application of MAE
• Factors affecting MAE
• Conclusion

3. INTRODUCTION
• Microwave-assisted extraction is an efficient
method which involves deriving natural
compounds from raw plants.
• Microwave extraction allows organic
compounds to be extracted more rapidly, with
similar or better yield as compared to
conventional extraction methods.

4. INTRODUCTION
• MAE of anthraquinone in pure alcohol at
60°C for 30mins gave a recovery of 65%
which resulted from 3 days maceration in pure
ethanol at room temperature.
• The advantages that MAE has over Soxhlet
are:
– Reduction in extraction time
– Improved yield
– Better accuracy
– Suitable for thermolabile substances

5. INTRODUCTION

6. MICROWAVE THEORY
• Microwaves are non-ionizing electromagnetic
waves of frequency between 300MHz to 300
GHz and positioned between the X-ray and
infrared rays in the electromagnetic spectrum.
• Microwaves serves two major purposes:
– Communication
– Energy vectors

7. MICROWAVE THEORY
• The energy vector application is the direct
action of waves on materials that has the
ability to convert a part of the absorbed
electromagnetic energy to heat energy.
• Microwaves are made up of two oscillating
perpendicular field’s i.e.
– Electric field
– Magnetic field

8. MICROWAVE THEORY
• In MAE, heating occurs in a targeted and
selective manner with practically no heat
being lost to the environment as the heating
occurs in a closed system.
• This unique heating mechanism significantly
reduces the extraction time (usually less than
30min) as compared to Soxhlet.

9. EXTRACTION PRINCIPLE
• Dried plants contain a minute microscopic
trace of moisture which serves as target for
microwave heating.
• High temperature and pressure is generated
inside the oven.
• High temperature causes dehydration of
cellulose which accounts for its reduction of
mechanical strength.

10. EXTRACTION PRINCIPLE
• The MAE process is as follows:
– Microwave radiation
– Moisture get heated up
– Moisture evaporates
– Generation of tremendous pressure on cell
wall
– Swelling of plant cell
– Rupture of the cell
– Leaching out of phyto-constituents
• This phenomenon can be intensified if the plant
matrix is impregnated with solvents with higher
heating efficiency under microwave.

11. INSTRUMENTS
• There are two types of commercially available
MAE systems:
– Closed extraction vessels
– Focused microwave ovens
• The former performs extraction under
controlled pressure and temperature.
• In the latter, only a part of the extraction
vessel containing the sample is irradiated with
microwave.

12. Open and Closed-vessel system

13. INSTRUMENTS
• Both systems are available as multi-mode and
single-mode.
• A multi-mode system allows evenly radiation
of sample by random dispersion of
microwaves.
• Single-mode (aka focused system) allows
focused radiation on a restricted zone by a
much stronger electric field.

14. INSTRUMENTS
• Both multi-mode and focused system
comprises of the following four components:
– Microwave generator: magnetron which
generates microwave energy
– Wave guide: propagate microwave to
microwave cavity
– The applicator: where the sample is placed
– Circulator : allow microwave to move in
forward direction

15. CLOSED VESSEL
• With closed vessel extraction, pressurised
microwave assisted extraction is performed under
pressure (with or without regulation).
• The pressure allows temperatures above boiling
points of the solvents to be reached enhancing
speed and efficiency.
• To avoid overpressure, power, temperature and
pressure can be controlled.
• When dealing with thermolabile compounds, high
temperature causes degradation of analytes.
Therefore, the open system is chosen.

17. Advantages of closed-vessel system
• Decreased in extraction time
• Loss of volatile substances is avoided
• Less solvent is required because no
evaporation occurs
• No hazardous fumes during acid
microwave since it is a closed vessel

18. Disadvantages of closed-vessel system
• High pressure used pose safety risks
• The usual constituent material of the vessel
does not allow high solution temperatures
• Addition of reagents is impossible since it is
a single step procedure
• Vessel must be cooled down before it can be
opened to prevent loss of volatile
constituents.

19. OPEN VESSEL
• Extraction is made at atmospheric pressure.
• The maximum possible temperature is
determined by the boiling point of the solvent
at that pressure.
• Losses of vapours are prevented by the
presence of a cooling system on the top of the
extraction vessel that causes condensation of
solvent vapours.
• Heating is homogenous and efficient.

21. Advantages of open-vessel system
• Increased safety
• Addition of reagent is possible
• Vessels made of various material can be
used
• Excess solvent can be removed easily
• Ability to process large samples
• No requirement for cooling down or
depressurisation
• Low cost of equipment
• Suitable for thermolabile products

22. Disadvantages of open-vessel system
• The ensuing method are less precise than
in close-vessel system
• The sample throughput is lower as open
system cannot process many samples
simultaneously
• Require longer time to achieve same
results as for closed system

23. APPLICATION OF MAE

24. APPLICATION OF MAE

25. FACTORS AFFECTING MAE
• Solvent - appropriate solvent is very
important for obtaining optimal extraction
yields.

26. FACTORS AFFECTING MAE
• Extraction time - by increasing extraction
time, quantity of analytes is increased but
there is the risk of degradation.

27. FACTORS AFFECTING MAE
• Microwave power - the power must be
correctly chosen to minimise the time
needed for extraction.
• However, increased power may cause
solvent loss by evaporation.
• Maximum power used ranges between
600W and 1000W for closed systems and
around 250Wfor open systems.

28. FACTORS AFFECTING MAE
• Matrix characteristics - the plant particle size
and the status in which it is presented for
MAE can affect the recoveries of
compounds.
• The particle sizes of the extracted materials
are generally in the range of 100m – 2mm.
• Fine powders enhance extraction as they
provide a larger surface area.

29. FACTORS AFFECTING MAE
• Temperature - temperature should be
sufficient to ensure good solubility of
compounds and a good penetration of
solvent in the plant matrix to enhance
extraction yield.
• However, it should not be too high
enough to degrade the target compounds.

30. CONCLUSION
• Chemical analysis of extracts from plant
material plays a central role in development
and modernization of herbal medicine.
• MAE has proven to be effective in all aspects
compared to traditional extraction techniques.
• More research is needed to improve the design
and scale up of the novel extraction systems for
their better industrial applications.

31. REFERENCES
• S. Hemalatha, 2007, Microwave Assisted Extraction
– An innovative and promising Extraction Tool for
Medical, Pharmacognosy Reviews, Vol 1-Issue 1
• Farid Chemat, Giancarlo Cravotto, 2012,
Microwave-assisted Extraction for Bioactive
Compounds: Theory and Practice, Ebook
• Mauricio A. Rostagno, Juliana M. Prado, 2013,
Natural Product Extraction: Principles and
Applications, Ebook
• YouTube videos:
– https://www.youtube.com/watch?v=oFSe4HaPgg
o
– https://www.youtube.com/watch?v=3Em9qU4_2
YE

32. THANK YOU