Silymarin Extraction from Milk Thistle – Most Efficient with Ultrasonication

Silymarin is determined as a group of flavonolignans present in the milk thistle plant. Silymarin is well-known for various medicinal effects and thereby used in pharmaceuticals and supplements. Ultrasonic extraction has been proven to be the most efficacious technique to isolate flavonolignans from milk thistle. Ultrasonic extractors give high yields of superior quality within a short processing time.

Ultrasonic Extraction of Silymarin from Milk Thistle Seeds

Milk thistle flowerSilymarin, a mixture of flavonolignans exhibiting many pharmacological activities, is obtained from the seeds of milk thistle plant (Silybum marianum L. Gaertner, Asteraceae). The isomeric mixture of polyphenolic flavonolignans in milk thistle seeds is known as silymarin and contains the polyphenols taxifolin, silychristin, silydianin, silybin A, silybin B, isosilybin A and isosilybin B.

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Ultrasonic extraction setup: Probe-type ultrasonicator UIP2000hdT (2000 watts) in a pharma-grade stainless steel reactor.

Ultrasonic extraction setup: Probe-type ultrasonicator UIP2000hdT (2000 watts) in a pharma-grade stainless steel reactor.

The Challenge of Silymarin Extraction:

The major amount of silymarin in Silybum marianum seeds is present in the cell walls, which are composed mainly of cellulose forming a rigid matrix. This rigid cell matrix is hard to break. Conventional solvent extraction (e.g. using ethanol, methanol or hexane) cannot break the cell walls completely so that a large amount of silymarin remains entrapped in the cell matrix and is not released into the solvent. This means that large quantities of valuable bioactive compounds are wasted due to inefficient extraction techniques.

The Solution for Efficacious Silymarin Extraction:

Ultrasonic extraction excels other extraction methods especially in high yields, short processing duration and its non-thermal treatment, i.e. low extraction temperature. The working principle of ultrasonication is based on acoustic cavitation. Acoustic a.k.a ultrasonic cavitation creates bubble implosions, intense shear forces, high pressure differentials and liquid jets. These purely mechanical forces disrupt even very rigid cell walls and release entrapped bioactive compounds such as silymarin into the surrounding solvent. Read more about the working principle of ultrasonic cavitation for extraction processes!
The low extraction temperature during ultrasonic extraction prevents the thermal degradation of bioactive compounds, so that their potency is fully maintained.

Advantages of Ultrasonic Extraction of Phytochemicals (e.g., silymarin)

  • High extraction yield
  • High-quality extract
  • Rapid process
  • Non-thermal treatment
  • Compatible with any solvent
  • Safe and easy to operate
  • Energy-efficient

Protocol for the Extraction of Silybum mariannum

Ultrasonic extractor UP400St for flavonolignans and silymarin extraction from milk thistle seeds.About 500 g of finely powdered seeds were extracted using n-hexane for 15 min. Ultrasonic probe with a tip diameter of 20 mm was employed for direct sonication (the horn tip position inside the extraction vessel was 1 cm under the solvent level). Extraction was carried out using an ultrasonic processor UP400S (400 watts, 24 kHz). Extraction was carried for 15 min at room temperature (temperature was monitored by a thermocouple inside extraction mixture by using an ice cooling bath around the extraction vessel to keep the temperature constant at 25°C ±5°C). After extraction, the extract was centrifuged at 4000rpm.
(cf. Sherif et al., 2017)
Alternatively, aqueous ethanol works excellent as solvent. Experiments confirmed that 70% ethanol as solvent gives the very high silymarin recoveries.

Ultrasonic extraction using a probe-type ultrasonicator of silymarin from milk thistle gives very high yields within short processing time.

HPLC chromatograms of Silybum marianum seeds extracted using an probe-type ultrasonicator at different time intervals of 15, 30, and 60min. Compounds detected: taxifolin, silychristin, silydianin, silybin A, silybin B, isosilybin A and isosilybin B.
(graphs and study: © Saleh et al., 2015)

Downstream Encapsulation: Preparation of Silymarin Nanogel with Ultrasound

Protocol for the Preparation of Silymarin-Nanostructured Lipid Carrier Gel
Silymarin-loaded nanostructured lipid carrier (NLCs) were prepared using solvent diffusion followed by ultrasonication method. The solvent diffusion is the most effective method for the preparation of the nanoparticles as it produces small particle size with low polydispersity whereas ultrasonication reduces shear stress. Lipid Sefsol® 218 (0.5% w/w) and Geleol® (1.4% w/w) were melted and dissolved in 2ml ethanol at 60ºC (organic phase). Silymarin approximately 2% w/w of lipid binary mixture was dissolved in the organic phase. Cremophor® RH40 (2.7% w/w) and bile salt (1.3% w/w) as surfactant and co-surfactant, respectively, were dissolved in 19ml distilled water heated at 70ºC and the organic phase was added to it with constant stirring at 70ºC to evaporate the organic solvent. The resultant emulsion was sonicated for 5 min using a probe-type ultrasonicator. In order to make a rheologically acceptable formulation for topical application, the dispersion of optimized freeze–dried silymarin NLCs was incorporated in Carbopol gel. (cf. Iqbal et al., 2019)

Ultrasonic probe for the extraction of silymarin from milk thistle seeds.

The ultrasonic extractor UP400St is a reliable device for the extraction of silymarin in 8L / 2 gal batches

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High-Performance Ultrasonic Processors for Silymarin Extraction

Hielscher Ultrasonics extractors are well established in the field of botanical extraction, no matter what plant materials or solvent is used. Extract producers – both, exclusive boutique extract manufacturers as well as large-scale mass producers – find at Hielscher‘s broad equipment range the ideal ultrasonic extraction equipment for their production requirements. Batch as well as continuous inline process setups are readily available and can be shipped off at the same day.

High Efficiency Extraction Equipment

Hielscher Ultrasonic extractors efficiently disrupt vegetable cells, increase the surface area of the plant material for solvent penetration, as well as improved mass transfer, which results in the quick and complete release of phytochemicals (secondary metabolites). Designed with regards to user-friendliness, Hielscher extractors are quickly installed and can be safe and intuitively operated.

Automatic Data Protocolling

Precise control over the ultrasonic process parameters by Hielscher Ultrasonics' intelligent softwareIn order to fulfil the production standards of food, nutritional supplement and therapeutic products, production processes must be detailed monitored and recorded. Hielscher Ultrasonics digital ultrasonic devices feature automatic data protocolling. Due to this smart feature, all important process parameters such as ultrasonic energy (total and net energy), temperature, pressure and time are automatically stored onto a built-in SD-card as soon as the device is switched on. Process monitoring and data recording are important for continuous process standardization and product quality. By accessing the automatically recorded process data, you can revise previous sonication runs and evaluate the outcome.
Another user-friendly feature is the browser remote control of our digital ultrasonic systems. Via remote browser control you can start, stop, adjust and monitor your ultrasonic processor remotely from anywhere.
Want to learn more about the advantages of ultrasonic extraction? Contact us now to discuss your botanical extract manufacturing process! Our well-experienced staff will be glad to share more information about ultrasonic extraction, our ultrasonic systems and pricing!

Fulfilling Highest Quality Standards – Designed & Manufactured in Germany

The sophisticated hardware and smart software of Hielscher ultrasonicators are designed to guarantee reliable ultrasonic extraction results from your botanical raw material with reproducible outcomes and user-friendly, safe operation. Robustness, reliability, 24/7 operation under full load and simple operation from the worker’s view are further quality factors, which make Hielscher ultrasonicators favourable.
Hielscher Ultrasonics extractors are used worldwide in high-quality phytochemical extraction. Proven to yield high-quality botanical compounds, Hielscher ultrasonic extractors are not only used by smaller crafters of specialty and boutique extracts, but mostly in the industrial production of widely commercial available extracts, nutritional supplements, and therapeutics. Due to their robust hardware and smart software, Hielscher ultrasonic processors can be easily operated and monitored.
Certified Quality: Hielscher Ultrasonics in Teltow, Germany is an owner-managed family business. Hielscher Ultrasonics is ISO certified. Of course, all standard Hielscher ultrasonicators are CE compliant and meet the requirements of UL, CSA and RoHs.

The table below gives you an indication of the approximate processing capacity of our ultrasonicators:

Batch Volume Flow Rate Recommended Devices
1 to 500mL 10 to 200mL/min UP100H
10 to 2000mL 20 to 400mL/min UP200Ht, UP400St
0.1 to 20L 0.2 to 4L/min UIP2000hdT
10 to 100L 2 to 10L/min UIP4000hdT
n.a. 10 to 100L/min UIP16000
n.a. larger cluster of UIP16000

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