ANSWER
Solvents for Plant Compounds Extraction
Specific parts of plants such as leaves, flowers, bark, seeds, fruits and root contain many active ingredients such as alkaloids, steroids, volatile oils, phenols, flavonoids and etc.The use of appropriate solvents is crucial for plant extraction.
According to studies, the types of phytochemicals extracted in various solvents are as follows:
| Solvent | Type of Phytochemicals |
| Cyclohexane | Waxes, Fats |
| Hexane | Waxes, Fats |
| Dichloromethane | Terpenoids, Alkaloids, Aglycones |
| Ethylacetate | Alkaloids, Aglycones, Glycosides |
| Acetone | Flavanols, Alkaloids, Aglycones |
| Ethanol | Tannins, Polyphenols, Flavonol, Terpenoids, Sterols, Alkaloids, Polyacetylenes, Propolis |
| Methanol | Saponins, Tannins, Phenones, Flavones, Sugars, Aminoacids, Anthocyanins, Terpenoids, Xanthoxyllines, Totarol, Quassinoids, Lactones, Polyphenols |
| Water | Sugar, Aminoacids, Saponins, Tannins, Lectins, Terpenoids, Anthocyanins, Starches, Polypeptides |
| Liquefied Carbon dioxide | Decaffeination of green coffee beans or tea, preparation of leaf extracts, extraction of spices, herbs, essential oils, pungent constituents, natural colorants, antioxidants, fatty oils. |
(Houghton & Raman, 1998; Cowan, 1999; Hans-Jőrg Bart, 2011).
Food Standard for Extraction Solvent (European Union)
According to the European Union, the following solvents are allowed if the products are to be used with foods:
(a) Water (with admixture of acids or base)
(b) Solvents like propane, butane, ethyl acetate, ethanol, carbon dioxide, acetone, nitrous oxide.
These solvents are to be used in compliance with good manufacturing practice for all uses.(1)
| Solvent |
| Propane |
| Butane |
| Ethyl acetate |
| Ethanol |
| Carbon dioxide |
| Acetone(2) |
| Nitrous oxide |
(1) An extraction solvent is considered as being used in compliance with good manufacturing practice if its use results only in the presence of residues or derivatives in technically unavoidable quantities presenting no danger to human health.
(2) The use of Acetone in the refining of olive-pomace oil is forbidden.
(c) Extraction solvents for which conditions of use are specified
| Solvent | Conditions of use (summary description of extraction) | Maximum residue limits in the extracted food ingredients |
| Hexane(1) | Production or fractionation of fats and oils and production of cocoa butter | 1mg/kg in fat, oil or cocoa butter |
| Preparation of defatted protein products and defatted flours | 10mg/kg in food containing defatted protein products and defatted flours | |
| 30mg/kg in the defatted soya products as sold to the final consumer | ||
| Preparation of defatted cereal germs | 5mg/kg in defatted cereal germs | |
| Methyl acetate | Decaffeination of, or removal of irritants and bitterings from coffee and tea | 20mg/kg in coffee or tea |
| Production of sugar from molasses | 1mg/kg in sugar | |
| Ethylmethylketone(2) | Fractionation of fats and oils | 5mg/kg in fat or oil |
| Decaffeination of, or removal of irritants and bitterings from coffee and tea | 20mg/kg in coffee or tea | |
| Dichloromethane | Decaffeination of, or removal of irritants and bitterings from coffee and tea | 2mg/kg in roasted coffee and 5mg/kg in tea |
| Methanol | For all uses | 10mg/kg |
| Propan-2-ol | For all uses | 10mg/kg |
(1) Hexane means a commercial product consisting essentially of acyclic saturated hydrocarbons containing six carbon atoms and distilling between 640C and 700C. The combined use of Hexane and Ethylmethylketone is forbidden.
(2) The level of n-Hexane in this solvent should not exceed 50mg/kg. The combined use of Hexane and Ethylmethylketone is forbidden.
(d) Extraction solvents in the preparation of flavourings from natural flavouring materials.
| Solvent | Maximum residue limits (mg/kg) |
| Diethyl ether | 2 |
| Hexane(1) | 1 |
| Cyclohexane | 1 |
| Methyl acetate | 1 |
| Butan-1-ol | 1 |
| Butan-2-ol | 1 |
| Ethylmethylketone(1) | 1 |
| Dichloromethane | 0.02 |
| Propan-1-ol | 1 |
| 1,1,1,2-tetrafluroethane | 0.02 |
(1) The combined use of Hexane and Ethylmethylketone is forbidden
(The Council Of The European Union, 2009).
References
Bart, H. J. (2011). Extraction of Natural Products from Plants – An Introduction.
Cowan, M. M. (1999). Plant products as antimicrobial agents. Clinical Microbiology, 12, 564-582.
Gupta, A., Naraniwal, M. & Kothari, V. (2012). Modern Extraction Methods For Preparation Of Bioactive Plant Extracts. International Journal of Applied and Natural Sciences, 1(1), 8-26.
Houghton, P. J., Raman, A. (1998). Laboratory Handbook for the Fractionation of Natural Extracts. London: Chapman and Hall.
The Council Of The European Union. (2009). Approximation of the laws of the Member States on extraction solvents used in the production of foodstuffs and food ingredients (Directive 2009/32/EC).
