Ultrasounds for vegetable extraction
Plants contain countless phyto-complexes for human and animal use which are of great interest for pharmaceutical, herbalist, cosmetic, health and food industries.
Extraction systems are exhaustive when the right combination of three important elements is carried out: preparation of the vegetable, extraction solvent and extraction method. Some traditional extraction techniques provide for the use of organic solvents, high temperatures and long maceration periods with negative outcomes which one may imagine: damage to health, the environment and deterioration to the active ingredients and vegetable matrices.
The ultrasonic extraction technique breaks the plant cell wall by means of cavitation thus increasing mass conveyance and penetration of the solvent. This enables acceleration of the extraction time achieved only by means of physical action.
Combining ultrasounds with traditional extraction systems enables:
Reduction of operating time;
Reduction of process temperatures;
Control of the use of solvents.
The aim of is to attain certified “organic” products and the advantages are in terms of:
Yield;
Ecology;
Energy consumption;
Conservation of the innate properties of the extract.
To sum up, we can utilize the following advantages from ultrasounds:
Use of any kind of liquid solvent, including oil, (depending on the product subjected to treatment, in some cases use of organic solvents is unnecessary);
Low extraction temperatures: prevention of inconveniences caused by high-temperature extraction (deterioration of thermolabile ingredients);
Reduction of extraction times compared to traditional techniques (extraction times with ultrasounds range from 10 minutes to 1 hour);
Total compatibility of the technology with all traditional extraction methods (in any phase);
Control of the process parameters (modulating time, frequency and ultrasonic power).
Some information on industrial vegetable extraction
The main vegetable extraction methods, based on osmosis and diffusion phenomena, used in laboratories and industries, can generally be summarized in:
Distillation;
Maceration;
Percolation;
Extraction with solvents.
The three main alternative industrial extraction technologies, which have high performance ecologically speaking and which respect substances, are:
Supercritical fluids (CO2): suitable for non-polar active ingredients (oils), non-polluting, very expensive;
Dynamic extractors (Naviglio Extractor):a mechanical device with pistons; it induces (during the “release” phase) a negative pressure gradient in the solid matrix, so that extraction is possible at ambient temperature in few cycles, i.e. in short periods of time (1-2 hours);
Ultrasounds: suitable for pre-treatment of vegetable matrices, non-polluting and comparatively low-cost.
Ultrasound Extraction test on hemp : leaves and inflorescences of Finola variety
Ultrasound extraction tests were performed on Finola hemp samples, both with fresh leaves and with dried leaves and inflorescences. A US Everywave Getwave system with max power 400W was used.
The extraction parameters follows:
Continuous ultrasound, 21kHz frequency, 60% power
Sonication time: 6min.
Maximum temperature: 60 ° C
Agitation with magnetic plate
solution: water / hydroalcoholic 50%
Here are reported the results of the tests, conducted up to now, represented in the chromatograms.
The tests were organized as follows:
- 'Blank': 24 hours of maceration in water (with mechanical stirring) without ultrasound treatment (in the sample table 1, 5, 8)
- Ultrasound treatment in water: 14 hours of soaking followed by 6min. US (sample 3,6,9)
- Ultrasound treatment in 50% hydroalcoholic solution: 14 hours of soaking followed by 6min. US (sample 4,7,10)
Analysis of the results
Results
A study of the chromatograms and the table shows that the inflorescences are characterized by a higher content of cannabinoids (slots 8 and 9), the greatest extraction of which was obtained in the samples subjected to the action of ultrasound both in water and even more with hydroalcoholic solution. Furthermore, the flavonoids (slots 2-4) are found in greater concentration in the leaves (usually considered as waste), also in this case the ultrasounds have allowed a greater extraction.
Overall, we can conclude that ultrasound allows for greater extraction of molecules of interest from hemp, in hydroalcoholic solution or simply in water. Therefore, the tests are interesting both with a view to using the US as an alternative cannabinoid extraction technology to supercritical fluids or with organic solvents, and for herbal or nutraceutical products.
LC-MS analysis performed at the Department of Chemistry of the University of Padua
Extraction of polyphenols from thyme (thimus vulgaris) with an ultrasonic reactor
An experimental test was conducted to obtain a rapid and complete extraction of polyphenols, optimizing the system in terms of:
- specific ultrasonic power (W / liter)
- amount of vegetable / dilution
- type of solvent: water, water and EtOH cosolvent (ethanol)
- sonication time and mode (continuous / intermittent)
The chemical analyzes are aimed at measuring the yield in total polyphenols, quite easy to identify, of great interest for pharmaceutical and nutriceutical applications, comparable with many literature data.
There is no mixing for ultrasonic extraction, as a very compact sonication cell is used.
The EW20S reactor consists of a main body ending with a 'barbell horn' type sonotrode and a compact flow cell, with a volume of approximately 100mL.
As regards the reference test (traditional maceration), the vegetable was immersed in the solvent at about 25 ° C for 48h.
Given the possibility of high specific powers involved, an external cooling system (ice) of the reactor was provided and the temperature rise was measured during the test, so as not to exceed 35 ° C for the vegetable mixture / solvent.
Main parameters for the optimized test:
Vegetal : THYME dry: density 0.21 g / l, 2 / 3mm, herbal tea cut
pre-treatment of veg.: 10 minutes of pre-immersion in water to soak the vegetables
solvent: H2O (60%) / EtOH (40%)
Vegetable / solvent dilution: 1/30
Power: 130W
temperature rise: about 15 ° C
Process type: BATCH, without mixing, with external cooling
reaction cell volume: 100mL
sonication time: 15min.
Results of chemical analysis
The results of the chemical analyzes on the extracts of the most significant tests follow.
The first set of analysis on the extraction tests was conducted with HPLC at a wavelength of 280 nm (characteristic for this class of compounds). In the figure relating to HPLC, the reference maceration test at room temperature is N 1, while the test optimized with ultrasound is N 11.
The trend of the graphs (quantity and height of the peaks) highlights the efficiency of ultrasound to extract various types of polyphenols in a few minutes (among these, various antioxidants: flavonoids known as proanthocyanidins, leucoanthocyanidins, piconogenols, tannins, etc., see following table).
After the first set of tests, the standard maceration and optimized US extractions were repeated and LC-MS (-) analyzes of the corresponding samples were performed. The relative chromatograms are almost identical (see figure: maceration N 17, ultrasound N 19), highlighting the total extraction capacity of the ultrasounds in reduced times. Very interesting is the analysis of the main polyphenols present in the extracts, listed in the table.
The analysis of the samples were carried out by the Institute of Biomolecular Chemistry of the C.N.R. of Padua, in the days immediately following that of the tests..
Conclusions
The results show an equivalent or greater extraction of polyphenols for the ultrasound test, compared to the extraction by traditional maceration.
Extraction of glycyric acid from licorice roots using an ultrasonic reactor
A series of ultrasonic extraction tests on licorice roots were performed to verify the extraction yields of polyphenols and glycyrrhizic acid, of high pharmacological interest.
The experimental setup of the ultrasonic reactor is such as to bring the process temperature even to high values, with the vessel under overpressure. There is no mixing for the ultrasonic extraction, as a very compact sonication cell is used: the EW20S reactor consists of a main body ending with a 'barbell horn' type sonotrode and a compact flow cell, about 100mL of useful volume for the solvent. The reactor can also be used as a flow cell, in order to treat larger volumes.
As regards the reference test (traditional maceration), the vegetable was immersed in the solvent at about 25 ° C for 48h.
Given the possibility of high specific powers involved, the temperature rise was measured during the tests, to identify the best extraction process temperature.
Main parameters for the optimized test
Matrices: LIQUORICE, root pieces, size 2-10cm
pre-treatment of the matrix: 10 minutes of pre-immersion in water to soak the vegetables
solvent: H2O (60%) / EtOH (40%)
Vegetable / solvent dilution: 1/30
Power 60-160W, depending on the chosen process
temperature rise: about 30-130 ° C, depending on the chosen process
Process type: BATCH without mixing (continuous recirculation tests give similar results)
reaction cell volume: 100mL
sonication time: 15min.
Results of chemical analyiss
The results of the chemical analysis on the extracts of the most significant tests follow.
The reference 48h maceration test is N 21, while the ultrasound optimized test is N 22.
The first set of analysis was conducted with HPLC at a wavelength of 280 and 320 nm: the trend of the graphs (quantity and height of the peaks) highlights the efficiency of the ultrasounds to extract in a few minutes a greater quantity of substances than standard maceration.
A second LC-MS analysis was then performed which also made it possible to identify the main polyphenols and glycyric acid (glycyrizin in the table)
The analyzes of the samples obtained were carried out by the Institute of Biomolecular Chemistry of the C.N.R. of Padua, in the days immediately following that of the tests.
Conclusions
From all the chromatographic spectra we note the greater richness of peaks of the US samples compared to the macerated ones. Furthermore, the results obtained from the LC-MS analysis have demonstrated the greater extractive power of US compared to maceration, in fact from the chromatogram it is possible to identify more than double the compounds, especially those with lighter weight, which have shorter retention times.
As for glycyrizic acid, which is of high industrial interest, ultrasounds have given very interesting results that allow yields up to 10% to be obtained.
Special Everywave systems for ultrasonic extraction
Everywave has designed and optimized two ultrasound system series:
Thanks to the scalability of ultrasonic processes, research results can be transferred to industrial-scale processes.
Laboratory systems
Everywave manufactures compact ultrasound systems GET:WAVE which sonicate liquid preparations in containers of various type; the specific sonication power (Watt/litre) is easily changed according to the user’s needs.
Special industrial systems
Everyware has designed special systems with flow cells and a tubular reactor, FLOW:WAVE and STEP:WAVE, for applying ultrasounds to vegetable extractions and macerations where high power or continuous-flow operating is required.
These systems can be used in specialized industrial sonochemistry thanks to:
High power which can reach 1000W/l;
Operating in overpressure conditions;
High temperatures up to 150°C.
Vegetable extraction tanks
EVERY WAVE has developed a line of TUB: WAVE® plant extraction tanks for the treatment of leaves, flowers, buds, seeds, fruit, roots and bark, both fresh and dried, through the use of both natural and organic solvents. .
The plant extraction technique using ultrasound allows to extract the active ingredients from medicinal plants for the production of high quality phytoextracts in the pharmaceutical, herbal, cosmetic, health and food sectors.
With TUB: WAVE the extraction cycles are very fast and are always performed at low temperatures, which allows to maintain the organoleptic properties of the vegetable raw materials.
Models available with tank of:
- 5 liters (for extractions from 2 to 5 liters)
- 20 liters (for extractions from 5 to 20 liters)
- 100-250 liters (for extractions from 20 to 250 liters)
