What are the extraction methods of plant extracts?

Plant extract is the carrier of modern plant medicine science and technology, is the main raw material of plant medicine preparation. At present, solvent extraction, ultrasonic extraction, microwave extraction and enzyme extraction are commonly used to extract plant extracts, while supercritical fluid extraction and microwave-assisted extraction are widely used as new extraction techniques.

  1. Solvent extraction method
    Solvent extraction method is to use solvent to extract active ingredients from solid raw materials. The solvent used must have the characteristics of mutual solubility with the extracted solute. After crushing the plant material, put it into a suitable container and add several times the amount of solvent, which can be extracted by immersion, percolation, decocting, reflux and continuous extraction.
    In the process of solvent extraction, the concentration of solvent, ratio of material to liquid, extraction temperature and extraction time will directly affect the extraction rate of active ingredients. Cristina Juan et al. extracted Ochratoxin A from rice by solvent extraction and determined OTA content by fluorescence detection and liquid chromatography, The results showed that the content of OTA in the extract was 4.17ng / g under the conditions of suitable ratio of material to liquid, extraction temperature and extraction time. Monte D. Holt used solvent extraction to extract alkyl resorcinol from raw and mature wheat seeds. The experiment showed that solvent extraction could save extraction time.
  2. Ultrasonic extraction method
    Ultrasonic extraction is the use of ultrasonic vibration and cavitation effect to accelerate the release of substances in plant cells, diffusion and dissolution into the solvent, while keeping the structure and biological activity of the extracted substances unchanged. The principle of ultrasonic extraction is mainly a physical process. It is a new extraction method which has been paid more attention in recent years. Compared with conventional solvent extraction, ultrasonic extraction can greatly shorten the extraction process, consume less solvent and have higher extraction rate, so it has higher extraction efficiency.
    In the ultrasonic extraction process, the choice and concentration of solvent, the ratio of material to liquid, the extraction temperature and the extraction time will directly affect the extraction rate. Ling Zhou et al. used ultrasonic extraction method to extract Schisandra chinensis, mainly studied the influence factors of ultrasonic extraction rate, the experimental study showed that the extraction rate increased with the increase of temperature and power. Hong Van Le used ultrasonic extraction of vitamin E and phenolic compounds in cherry. The difference of extraction time and extraction rate between ultrasonic extraction method and enzyme extraction method was mainly compared. The experimental results showed that the time of ultrasonic extraction was 6 times shorter than that of enzyme extraction, and the extraction rate of ultrasound extraction was 2 ~ 3 times of that of enzymatic extraction. Zhong Aiguo et al used ultrasonic extraction method of chlorophyll from fresh bamboo leaves to quantitatively determine the content of chlorophyll extracted by spectrophotometer. The results showed that the ultrasonic extraction method not only has higher extraction rate, higher speed and higher efficiency, but also can be extracted at room temperature without heating and save energy.
  3. Supercritical fluid extraction
    Supercritical fluid extraction (SFE) is a new kind of extraction and separation technology, usually using CO2 as extraction agent. The principle of supercritical fluid extraction is to use the unique solubility of supercritical fluids and the solubility of substances in supercritical fluids is very sensitive to changes in pressure and temperature. The substances dissolved in the supercritical fluid are separated by means of raising temperature and lowering pressure (or both) to achieve the purpose of separation and purification. It is considered as a new and green separation technology, especially suitable for the separation and purification of unstable natural products and physiological active substances.
    In the middle of 1980s, supercritical CO2 extraction technology was gradually applied to the extraction and separation of active components from plants. It is a new technology which has been researched and applied successfully. Ruey Chi Hsu et al extracted the active ingredient of Ganoderma lucidum by supercritical fluid extraction with CO2 and ethanol as solvents. The results showed that supercritical fluid extraction ensured the fluidity of Ganoderma lucidum extract and was not affected by temperature. Monica Waldeb.ck et al. extracted squalene and alpha-tocopherol from olives by pressurized fluid extraction. The results showed that the extraction effect was better when the solvent was ethanol, the extraction temperature was 190 °C and the extraction time was 10 min. YI QI ANG GE Vitamin E was extracted from wheat germ by supercritical CO2 extraction. The effects of pretreatment and extraction conditions on yield were studied. The experimental results showed that the extraction rate was higher when the particle size was 30 nets, the pressure was 4000 ~ 5000 psi, the extraction temperature was 40 ~ 50 °C and the CO2 flow rate was 2.0 mL / min.
  4. Microwave assisted extraction
    Microwave assisted extraction (MAE) is a new technology which uses microwave energy to improve the extraction efficiency. Microwave-assisted extraction (MAE) is a method of selective extraction of target components from materials by using the characteristics of microwave heating. By adjusting the parameters of microwave, the target components can be heated effectively to facilitate the extraction and separation of target ingredients. The principle of microwave-assisted extraction is that plant samples absorb a large amount of energy in the microwave field, while the surrounding solvents absorb less, resulting in thermal stress within the cell. Plant cells are ruptured due to internal thermal stress, so that the substances inside the cells directly contact the relatively cold extraction solvent, which accelerates the transfer of target products from the cell to the extraction solvent, thus strengthening the extraction process. Microwave-assisted extraction technology uses heat in principle as well as soaking and filtration, but extracts plant extracts much faster than traditional methods. Reduce extraction time while avoiding destruction and degradation of valuable plant extracts.
    At present, microwave-assisted extraction (MAE) has become a powerful tool for extracting active ingredients from natural plants because of its fast extraction speed and better extraction quality. But the microwave-assisted extraction method is selective internal heating and requires the material to be treated to have good water absorption, In other words, the position of the product to be separated is easy to absorb water, otherwise the cell can not absorb enough microwave to break itself, the product is difficult to quickly release. For the liquid extraction system, the solvent material is required to have polarity, and the non-polar solvent is not sensitive to the effect of microwave. The flavonoids and coumarins extracted from medicinal plants were extracted by microwave assisted extraction. The effects of sample size, ratio of material to liquid, extraction temperature and time on the extraction rate were studied by orthogonal experiments. The experimental results showed that under the optimum extraction conditions, extraction rate was 98.7%. Li Haibin et al extracted mogrosides from dried Siraitia grosvenorii by microwave-assisted extraction method. The results showed that the extraction rate of MAE was 70.5%, 45% higher than the conventional water extraction method, and the time was 50% shorter.
  5. Microwave and ultrasonic synergetic extraction
    Microwave is a kind of non-ionizing electromagnetic radiation. The polar molecules of the radiated material are quickly turned and aligned in the microwave electromagnetic field, resulting in tearing and mutual friction, causing heat. However, the penetration depth of microwave is limited (in the same order of magnitude with its wavelength), and its mass transfer function is not obvious in the enhanced extraction process. Ultrasonic wave is a kind of high frequency mechanical wave, which has turbulence effect, perturbation effect, interface effect and shaped energy effect. But the thermal effect produced by ultrasonic is not obvious and is confined in the very small area around cavitation bubble. When they are combined, the synergetic effect is beneficial to the release of wall-breaking components. That is to say, a cheap and non-polluting extraction method of bioactive substances can be obtained by the synergistic enhancement of microwave and ultrasonic extraction technology. HeJT et al., using microwave and ultrasonic field synergetic extraction of water-soluble bioactive components from traditional Chinese medicine, have achieved good results. Luo Feng et al extracted flavonoids from Glycyrrhiza uralensis Fisch by microwave and ultrasonic assisted extraction. Ma Lihua et al studied the effect of traditional distillation and microwave ultrasonic extraction on the extraction rate of carotenoids from Arctium lappa L., and determined the best extraction conditions by orthogonal experiment. Bai Hongjin and the like used anhydrous ethanol distilled water and anhydrous-distilled water (with a volume ratio of 1 ∶ 1) as solvents, respectively, The antioxidant effects of aloe extract on rapeseed oil, lard, cottonseed oil and sunflower oil were determined by using microwave and ultrasound assisted extraction.
  6. Enzyme extraction method
    The cell walls of natural plants are made of cellulose, in which the active components of plants are often encased in the cell walls. Enzyme extraction method is a method of using cellulase, pectinase, protease and so on (mainly cellulases) to destroy the cell wall of the plant, in order to promote the dissolution of plant active components in a large extent. In the process of enzymatic extraction, the selection of enzyme, enzyme concentration, pH value, enzymatic temperature and enzymatic time will affect the extraction rate of plant extracts.
    E. BARZANA et al. extracted carotenoids from marigold by enzyme extraction method. The effects of ratio of material to liquid, enzyme concentration, time and temperature on extraction rate were studied. The results showed that the optimal extraction process was as follows: 1 ∶ 4, enzyme concentration 0.3%, extraction time 1.5 h, temperature 25 °C. Zhang Xiaoqing et al used enzyme extraction method to extract flavonoids from ginkgo biloba. Through orthogonal experiment, the optimum process conditions of enzyme concentration, pH value, temperature and time were found.

Hongjitang as a China plant extract manufacturer can always support advanced extract technology and produce nature quality extracts.

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