Extraction of natural products

Mukhopadhyay, Natural Extracts Using Supercritical Carbon Dioxide, CRC Press, Boca Raton, Fla., 2000 Moyler, Extraction of flavours and fragrances with compressed CO2, in Extraction of Natural Products Using Near-Critical Solvents, King and Bott (eds.), Blackie Academic Professional, London, 1993. 

Lack A and Seidlitz H. 1993. Commercial scale decaffeination of coffee and tea using supercritical CCb. In King MB and Bott TR, editors. Extraction of natural products using near-critical solvents. Glasgow Blackie Academic, p. 101—139. 

Moyler, D. A. in King, M. B. and Bott, T. R. (eds) Extraction of Natural Products using near-critical Solvents. (Chapman Hall, Glasgow, 1993)... 

Li, G., Hu, Z. (1998). Separation and identification of active components in the extract of natural products by microemulsion electrokinetic chromatography. Analyst 123 1501-1505. 

As its name suggests, supercritical fluid extraction (SEE) relies on the solubilizing properties of supercritical fluids. The lower viscosities and higher diffusion rates of supercritical fluids, when compared with those of liquids, make them ideal for the extraction of diffusion-controlled matrices, such as plant tissues. Advantages of the method are lower solvent consumption, controllable selectivity, and less thermal or chemical degradation than methods such as Soxhlet extraction. Numerous applications in the extraction of natural products have been reported, with supercritical carbon dioxide being the most widely used extraction solvent. However, to allow for the extraction of polar compounds such as flavonoids, polar solvents (like methanol) have to be added as modifiers. There is consequently a substantial reduction in selectivity. This explains why there are relatively few applications to polyphenols in the literature. Even with pressures of up to 689 bar and 20% modifier (usually methanol) in the extraction fluid, yields of polyphenolic compounds remain low, as shown for marigold Calendula officinalis, Asteraceae) and chamomile Matricaria recutita, Asteraceae). " ... 

Modey, W.K., Mulholland, D.A., and Raynor, M.W., Analytical supercritical fluid extraction of natural products, Phytochem. Anal, 7, 1, 1996. 

M.B. King and T.R. Bott, Extraction of Natural Products using Near-critical Solvents, Blackie A. P., Glasgow, 1993. 

R. Eggers in Extraction of Natural Products Using Near-critical Solvents (ed. M.B. King, T.R. Bott) Chapter 8, Blackie Academic Professional, Glasgow UK, 1993... 

The current trend of consumer preference towards natural products requires new processing methods for spice-oils and extracts, without the addition of external material. In recent years there has been an increased interest in supercritical and subcritical extraction [26,27], which use carbon dioxide as a solvent [34,35,36]. Carbon dioxide (CO2) is an ideal solvent for the extraction of natural products because it is non-toxic, non-explosive, readily... 

There have been reported numerous advantages of SFE for the extraction of natural products including reduction of extraction cost and time, environmental acceptance, and lack of toxicity to human health compared with conventional organic solvent extraction. However, the high polarity of alkaloids due to salt formation in plant tissue has made it difficult to extract them using SFE. In order to develop a universally acceptable SFE method for alkaloids present in plant materials, a basified modifier has been introduced to the SFE of selected alkaloids. On the basis of these results, it is believed that SFE using basified modifiers can be used as an alternative to conventional solvent extraction for alkaloids from plant material. 

E Lack and H Seidlitz, Commercial scale decaffeination of coffee and tea using supercritical COr In Extraction of Natural Products using Near-critical Solvents MB King and TR Bott, Ed., Chapman Hall, London, UK, 1993, pp 101-139. 

Recent methods for extraction of natural products using microwave energy, i.e. 

The solute is disseminated in a solid matrix in the most of the supercritical extractions of natural products. If the interactions between solute and solid matrix are not important, the mass transfer models can be developed from the equations of microscope balances to a volume element of the extractor. If the mass transfer resistance is in its solid phases, the mathematical models must consider the solute transport within the solid particles or the surface phenomena. 

Some attempts are being made to model the supercritical extraction of natural products. Most of the models proposed consider the rate of extraction determined by the rate of mass transfer out of the matrix the solute is present in small amounts in the matrix, and during extraction the concentration of the solute in the supercritical fluid is well below the solubility limit (Brunner, 1984 Bartle et al, 1990 Reverchon et al, 1993 and Catchpole et al, 1994). 

Shirsatha, S.R., Sonawanea, S.H., Gogate, P.R. Intensification of extraction of natural products using ultrasonic irradiations-a review of current status. Chem. Eng. Process. 53, 10-23 (2012)... 

Most of the recent literature in this field is concerned with synthetic organic reactions, supramolecular chemistry and crystal engineering. However, solvent free approaches can also be used in the extraction of natural products, although less information is available in the mainstream literature. Juice extractors can be used to afford aqueous solutions of biologically active compounds from undried plant material. An extract of Capsicum annum L. was recently prepared in this way, and then used in the green synthesis of silver nanoparticles. The actual synthesis of the nanoparticles was conducted in the aqueous phase and therefore this work will not be discussed further here. However, this solvent free approach to extraction is probably worthy of greater representation in the green chemistry literature. 

Microwave treatment, because of its rapid heating of materials, is being explored in a multitude of crops for enzyme inactivation (25-28), for extraction of natural products (29), and oil and fat extraction from seeds and food products (30-32). Microwave treatment of peanut seed prior to press extraction increased oil recovery approximately 10% at an optimum treatment time of 30 seconds (30). However, free fatty acid content initially increased with exposure time as well as peroxide value (30). Research on use of microwave treatment in blanching of peanuts indicated an influence on oil stability depending on treatment conditions (33). 

The studies most commonly identified with supercritical fluids and critical phase behavior are those concerned with extraction of natural products. No review of this subject would be complete without... 

Smith, R. M. 1995. Supercritical fluid extraction of natural products, LC-GC, 13 930-939. 

Clifford AA, Basile A, Jimenez-Carmona MM, Al-Said SHR. Extraction of natural products with superheated water. Proceedings of the GVC-Fachaussschuss Hochdruckverfahrenstechnik, 1999 181-184. 

King MB, Bott TR, eds. Extraction of Natural Products Using Near-Critical Solvents. London Blackie Academic, 1993. 

The sample preparation and FIPLC analysis are more elaborate for formulations with multiple APIs (e.g., over-the-counter (OTC) products) or with natural products. Examples of HPLC analysis of two OTC multi-vitamin products are shown in Figure 6.5, with a summary of method performance for both water-soluble and fat-soluble vitamins17 listed in Table 6.5. Other examples of HPLC analysis of extracts of natural products (white and red ginseng)18 are... 

J. R. J. Pare and J. M. R. Belanger, Microwave-Assisted Process (MAP ) Applications to the Extraction of Natural Products , Proc. 28th... 

A large body of experimental data has been accumulated on the solubility and extractability of natural products, such as steroids, alkaloids, anticancer agents, oils from seeds, and caffeine from coffee beans, in various SCF solvents such as CO2, ethane, ethylene, and N2O. Carbon dioxide is probably the most widely investigated SCF solvent since its critical temperature T = 31.1°C) makes it an ideal solvent for extracting materials that are thermally labile. Also, CO2 is nontoxic, nonflammable, environmentally acceptable, and inexpensive. 

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