Solvents for Ultrasonic Extraction from Plants

  • Ultrasonic extraction features many advantages such as high yields, fast extraction rates, environmental-friendliness and low energy consumption.
  • One of the strongest benefits is the use of water as extraction medium. However, sonication can be used with manifold solvent systems to deliver superior results for the targeted extract.
  • The optimal solvent for ultrasonic extraction of vegetal bioactives is chosen in regards to the raw material.

Extracción ultrasónica

Ultrasound is well known to disrupt cell structures and to improve mass transfer, thus increasing the extractability of biocompounds (e.g. phenolics, carotenoids).
Since the mechanical effects of sonication enhance the extraction process due to improved mass transfer greatly, the use of organic solvents is often superfluous. This means that for ultrasonic extraction, water is often a sufficient extraction medium which has many benefits such as being inexpensive, non-hazardous, easily available and environmental-friendly.
However, for specific bioactive compounds best results may be achieved by ultrasonic extraction in combination with a volatile solvent.
To choose the right solvent, the raw material (e.g. fresh or dried, macerated/grinded or powdered plant material) and the targeted substances (e.g. lipophilic, hydrophilic) must be considered.
 

TIn this video, we demonstrate you the advantages of extracting potent bioactive compounds from herbal leaves in glycerine using a probe-type sonicator. The challenge at hand is the high viscosity of vegetable glycerine, approximately 1400cP at room temperature, which may be a viscosity that many sonicators cannot handle. However, the 400watts powerful probe-type sonicator UP400St effortlessly handles this viscous solvent, ensuring thorough mixing and efficient extraction even with pure vegetable glycerine.
Vegetable glycerine is an ideal extraction solvent due to its non-toxic, non-irritating properties and its ability to preserve the stability and potency of sensitive bioactive compounds. Both, pure glycerine and glycerine-water mixtures, are useful solvents for the production of extracts for supplements and nutraceuticals, flavor extracts, food additives and cosmetics.

Ultrasonic Botanical Extraction using Glycerine as Solvent - UP400St

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Ultrasonic bench top sonicator UIP2000hdT for botanical extraction from leaves and flowers. This sonicator operates at a frequency of 20kHz and delivers 2000 watts for the most efficient extraction of bioactive compounds.

UIP2000hdT sonicator for botanical extraction in large batches or inline operation

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The following table lists several solvents, which are well established extraction solvents and are used for the ultrasonic extraction from plant material.

EthanolOne of the most common solvents for botanical extraction. As a polar solvent, ethanol dissolves polar compounds such as alkaloids and flavonoids.
WaterThe universal solvent, often used for extracting hydrophilic compounds like polysaccharides, proteins, and some glycosides.
Aqueous EthanolA mixture of ethanol and water, this solvent can extract a wide range of polar and moderately polar compounds, providing a balance between the solvent power of ethanol and the ability of water to extract hydrophilic compounds. Aqueous ethanol can be prepared at different ratios adjusting the dissolving capacity to target compounds.
GlycerineA highly polar solvent that is useful for extracting polar compounds and can be a safer alternative to other polar solvents, often used in tinctures and extracts meant for internal consumption. Read more about extracting phytochemicals in glycerine using sonication!
MethanolA highly polar solvent effective in extracting a wide range of plant compounds including phenolics, flavonoids, and some alkaloids.
HexaneA non-polar solvent used primarily for extracting non-polar compounds such as lipids, waxes, and essential oils.
AcetoneA polar aprotic solvent, acetone is effective for extracting a wide range of botanical compounds, particularly those that are less polar than those extracted by water or methanol.
IsopropanolA polar solvent similar to ethanol, commonly used for extracting essential oils, resins, and some alkaloids.
ChloroformA non-polar solvent effective in extracting alkaloids, terpenoids, and some glycosides. It is less commonly used due to its toxicity.
Ethyl AcetateA moderately polar solvent used for extracting a range of compounds including flavonoids, alkaloids, and phenolics.
TolueneA non-polar solvent used for extracting non-polar compounds such as essential oils, terpenes, and waxes.
ButanolA moderately polar solvent effective in extracting medium-polarity compounds including some glycosides and saponins.
Petroleum EtherA non-polar solvent primarily used for extracting fats, oils, and other non-polar compounds from plant materials.

 

In this presentation we introduce you to the manufacturing of botanical extracts. We explain the challenges of producing high-quality botanical extracts and how a sonicator can help you to overcome these challenges. This presentation will show you how ultrasonic extraction works. You will learn, what benefits you can expect using a sonicator for extraction and how you can implement an ultrasonic extractor into your extract production.

Ultrasonic Botanical Extraction - How to use sonicators to extract botanical compounds

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Ultrasonic extraction is works by disrupting cell structures and promoting mass transfer. This working principle of ultrasound is used by Hielscher Ultrasonics equipment for highly efficient extraction of bioactive compounds from plants.

Powerful ultrasound waves disrupt the cell matrix of biological structures and release the bioactive compounds. Mass transfer between the plant material and the solvent is intensified. Due to these mechanisms, ultrasonic extraction is highly efficient for botanical extraction.

UP400ST ultrasonic homogenizer for herbal extraction. The UP400St sovereignly handles solvents with higher viscosities such as 100% glycerine.

UP400ST ultrasonic homogenizer for herbal extraction allows to use the solvent of your choice.

Ultrasonicators for Extraction

Industrial sonicator for large scale botanical extractionFrom lab and bench-top ultrasonic devices up to full-industrial ultrasonic extraction systemsHielscher Ultrasonics is you long-time experienced partner, when it comes to powerful and reliable ultrasonic devices for successful extraction processes.
Our ultrasonic systems are widely used in biochemical laboratories and pharmaceutical production plants. The ultrasonic sonotrodes and reactors are autoclavable and fulfil the standards of pharmaceutical production.

Hielscher industrial sonicators can deliver very high amplitudes in order to disrupt cell matrices and to release targeted substances. Amplitudes of up to 200µm can be easily continuously run in 24/7 operation. The power and robustness of Hielscher ultrasonicators ensure high yields, fast extraction rates and more complete extractionexcelling conventional extraction processes.
Our ultrasonic processors can be combined with conventional extraction methods such as Soxhlet extraction or supercritical CO2 extraction. Retrofitting into existing production lines can be easily accomplished.

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In this short video clip, we demonstrate you the rapid ultrasonic infusion of liquor with lilac flowers. Ultrasonic infusion and extraction is used to transfer the wonderful flavor bouquets of flowers and blossoms into spirits, cocktails and non-alcoholic beverages. Watch how the UP200Ht sonicator releases the aroma and flavors of lilac into gin.

Lilac-Infused Gin for Exquisite Flavors using the Probe-Type Sonicator UP200Ht

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Ultrasonic Extraction by Cavitation

Intense ultrasound waves generate acoustic cavitation in liquids. The cavitational shear forces breaks cell wall and membranes so that the intracellular material is released. Ultrasonic extraction achieves greater penetration of the solvent into a vegetal tissue and improves the mass transfer. Thereby, ultrasonic extraction intensifies the extraction process significantly resulting in higher yields, faster extraction rates and a more complete extraction.

Solvent Systems

For the extraction of bioactive compounds from vegetal material various solvent systems are available. For the extraction of hydrophilic compounds, mostly polar solvents such as methanol, ethanol or ethyl-acetate are chosen, whilst for the extraction of lipophilic compounds (e.g. lipids), solvent systems such as dichloromethane or dichloromethane/methanol (v/v 1:1) are preferred. Hexane is often used as solvent for chlorophyll extraction.

What are Bioactive Compounds?

Bioactive compounds or phytochemicals are defined as substances, which have impact on living organisms, tissues, or cells. Biologically active substances include antibiotics, enzymes, and vitamins. Bioactive substances such as carotenoids and polyphenols can be extracted e.g. from fruits, leafs and vegetables, whilst phytosterols are found in vegetal oils.
Plant-derived bioactive compounds include flavonoids, caffeine, carotenoids, choline, dithiolthiones, phytosterols, polysaccharides, phytoestrogens, glucosinolates, polyphenols, and anthocyanins. Many bioactive substances are valued for acting as antioxidants and are therefore considered as health beneficial.

How do I select the best Extraction Solvent?

The guidelines below help you to select a suitable solvent for ultrasonic botanical extraction. As sonication is compatible with any standard solvent, you can select the solvent most ideal for your plant raw material, the targeted phytochemicals and cost-efficiency.

  • Selectivity: Select a solvent that specifically dissolves the desired compounds while leaving unwanted components behind. For instance, use ethanol for polar compounds like alkaloids and flavonoids.
  • Solubility: Based on the principlelike dissolves like,choose a solvent with a polarity similar to that of the solute. Polar solvents (e.g., water, ethanol) dissolve polar compounds, while non-polar solvents (e.g., hexane) dissolve non-polar compounds like lipids and oils.
  • Cost: Consider the cost-effectiveness of the solvent. Some solvents might be more expensive but offer higher yields or better selectivity, balancing the overall extraction cost.
  • Safety: Ensure the solvent is safe for use and handling. Factors include toxicity, flammability, and environmental impact. For example, water and ethanol are safer choices compared to chloroform or toluene.

Polarity and Solvent Selection
According to the law of similarity and intermiscibility, solvents with a polarity value near to the polarity of the solute are likely to perform better. Here are some examples:

  • Polar Solvents: Water, Ethanol, MethanolUsed for extracting polar compounds such as alkaloids, flavonoids, glycosides, and proteins.
  • Moderately Polar Solvents: Acetone, Ethyl Acetate, IsopropanolSuitable for extracting a wide range of compounds, including phenolics and some alkaloids.
  • Non-Polar Solvents: Hexane, Toluene, Petroleum EtherIdeal for extracting non-polar compounds such as lipids, waxes, terpenes, and essential oils.

Examples of Solvent Use

  • Ethanol: One of the most common solvents for botanical extraction. As a polar solvent, ethanol dissolves polar compounds such as alkaloids and flavonoids.
  • Water: The universal solvent, often used for extracting hydrophilic compounds like polysaccharides, proteins, and some glycosides.
  • Methanol: A highly polar solvent effective in extracting a wide range of plant compounds including phenolics, flavonoids, and some alkaloids.
  • Hexane: A non-polar solvent used primarily for extracting non-polar compounds such as lipids, waxes, and essential oils.
  • Acetone: A polar aprotic solvent, acetone is effective for extracting a wide range of botanical compounds, particularly those that are less polar than those extracted by water or methanol.
  • Isopropanol: A polar solvent similar to ethanol, commonly used for extracting essential oils, resins, and some alkaloids.
  • Chloroform: A non-polar solvent effective in extracting alkaloids, terpenoids, and some glycosides. It is less commonly used due to its toxicity.
  • Ethyl Acetate: A moderately polar solvent used for extracting a range of compounds including flavonoids, alkaloids, and phenolics.
  • Toluene: A non-polar solvent used for extracting non-polar compounds such as essential oils, terpenes, and waxes.
  • Butanol: A moderately polar solvent effective in extracting medium-polarity compounds including some glycosides and saponins.
  • Petroleum Ether: A non-polar solvent primarily used for extracting fats, oils, and other non-polar compounds from plant materials.

The following solvents were tested in research studies investigating ultrasonic extraction of specific plant materials and phytochemicals.

SolventPlantKind of tissue
Acetic acid / urea / cetyltrim-ethylammonium bromidericebran
Aqueous ethanoldistiller’s graingrain
Aqueous isopropanolsoybean, rapeseedseeds
EthanolSaccharina japonica
Glacial actic acidsorghum
Phenoltomato / potato / aloe vera / soybeanpollen / tuber / leaf / seed
Phenol/ammonium acetatebarley / bananaroot / leaf
Phenol/ammonium acetateavocado / tomato / orange / banana / pear / grape / apple / strawberryfruits
Phenol/methanol-ammonium acetateconiferous / banana / apple / potatoseed / fruits
Sodium dodecyl sulphate/acetoneconiferous / potatoseed / tuber
Sodium dodecyl sulphate/TCA/acetoneapple / bananatissue
TCAbeansanther
TCA/acetonecitrus / soybean / aloe veraleafs
TCA/acetonesoybean / coniferousseeds
TCA/acetonetomatopollen grain
TCA/acetone/phenololive / bamboo / grape / lemonleafs
TCA/acetone/phenolapple / orange / tomatofruits
Thiourea/ureasoybeanseed
Thiourea/ureaapple / bananatissues
Tris-HCL buffertomatopollen grain

What are Organic Solvents?

An organic solvent is a type of volatile organic compound (VOC). VOCs are organic chemicals which vaporise at room temperature.
Organic compounds used as solvents include:

  • aromatic compounds, e.g. benzene and toluene
  • alcohols, e.g. methanol
  • esters and ethers
  • ketones, e.g. acetone
  • amines
  • nitrated and halogenated hydrocarbons

Many organic solvents are classified as toxic or carcinogenic. In case of incorrect handling, they can be hazardous to humans and can contaminate air, water, and soil. Due to the powerful mechanism of ultrasonic extraction, the use of organic solvents can be avoided replacing them with milder, non-toxic solvents.

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