Extraction Procedures - Plant-based Materials

Other extraction procedures are used for determining (i) oils, fats and waxes (ii) fibre, lignin, cellulose, nitrogen-free extract and starch (iii) in vitro 

Fat includes triglycerides, sterols, lecithins (phospholipids), essential oils, fat-soluble pigments such as chlorophyll, and similar substances. The AOAC recommends that anhydrous diethyl ether kept over freshly cut sodium pieces is used for the extractant (Padmore, 1990, p. 79), but we prefer to use petroleum spirit, also called light petroleum and petroleum ether, with a boiling range of 40-60°C, as it is a less hazardous solvent. 

For multiple samples (c. 5 g) of seeds such as oilseed rape, another approach is to crush them and enclose them in small packets of pre-dried Whatman No. 4 filter circles, which are then stapled, labelled with a pencil and weighed. From 10 to 16 of these packets may be extracted in one large 

600 ml Soxhiet with a 2-litre flask. In this case, the packets are reweighed, and the weight loss gives the crude oil content (Hughes, 1969). 

This method published by MAFF (1993a) is not applicable to oilseeds or compound feeds containing milk powder. The sample is extracted with light petroleum and the residue then heated with 3 M HCl. This is filtered, washed, dried and re-extracted with light petroleum. 

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The methodology used to analyze these compounds in plant-based materials, generally, includes a series of steps ranging from exhaustive solvent extraction, clean-up of extracts, and preconcentration procedures to simple filtration and centrifugation in liquid samples. After the extraction procedures, the phenolic compounds are characterized and quantified [7, 8]. Various complex analytical methods have been used for the determination of these compounds in natural samples and the most important of them are described in detail in this chapter. 

Although there were some differences on the effects of temperature and pressure according to each particular compound, the free bases of hyoscyamine (1), scopolamine (2), and pseudoephedrine (6) were all found to be highly soluble in supercritical CO,. However, the hydrochloride salts of these compounds were scarcely extracted by pure CO, under any conditions employed. These results were consistent with preliminary evidence indicating that these alkaloids are not extracted from plant materials by pure CO,. This means that the alkaloids in living cells in the plant are not in the form of their free bases but rather as water-soluble salts in the cell vacuole [40]. Therefore, it was necessary to develop a procedure to enhance the solubilities of alkaloidal salts in CO,. 

The selection of an extraction procedure depends primarily on the class of compounds of interest as well as the type and physical state of the sample. Liquid samples generally do not require extraction prior to analysis however liquid-liquid extraction may be performed to isolate a certain class of compounds. Extraction of antioxidants from solid plant materials is most commonly done using aqueous mixtures of organic solvents. This is based on the principle that, upon extraction. 

Typical sequential extraction procedures employed for soils, sediment, and waste materials are based on the five-stage procedure of Tessier et al. [61]. For plant material (e.g., aquatic moss [3] and spinach [4]), sequential analysis with the use of water, EDTA, petroleum ether, ethyl acetate, butanol, methanol, and... 

As a result of a detailed collaborative investigation between the Chemistry Department of the University of Nottingham (Crombie, Whiting) and the U.N. Narcotics Laboratory (Szendrei), at least 14 cathedulin alkaloids have been isolated and formulated (46,47). Plant material collected in Kenya, Ethiopia, and the Yemen Arab Republic was extracted as fresh material, as freeze-dried material, and as sun-dried material. A number of extraction procedures were also employed, with methods directed toward the isolation of weak bases. In one procedure fresh material was extracted with ethanol in the presence of sodium bicarbonate, and the diluted extract was adjusted to pH 5.5 and extracted with... 

Since lupin seeds are used in some areas in cattle feeding, it is of practical as well as theoretical interest to determine the stage at which the seeds will be rich in the alkaloidal material responsible for toxicity. It has also been important to devise methods for the removal of alkaloids from the seeds so that the detoxified or debittered material can still be used as feed (111). Extraction procedures which accent the recovery of non-alkaloidal material have less interest to the alkaloid chemist than those which provide for the isolation of the pure organic bases. Given below are typical examples of the extraction procedures employed for the isolation of the lupin alkaloids lupinine, cytisine, Z-sparteine, d-lupanine, and anagyrine. The methods selected are representative of those utilized for the isolation of the less abundant or well-known lupin alkaloids as well. These methods are also representative of the different quantities of materials which are handled. One of the methods was selected (for anagyrine) to indicate some of the complexities of separation when there are a number of alkaloids present in a plant, rather than only one main alkaloidal constituent. The techniques of fractional distillation of the bases, fractional crystallization of alkaloid salts, such as perchlorates and picrates, and extractions dependent upon differential solubility have been employed for the isolation of pure individual alkaloids from a mixture. 

Back to Namre is the present day mantra of the modem world. The current trend is to find out new materials based on natural substances. Increased environmental awareness and the current economic simations tempt the modem man to make use of Natural fibres in developing new composite materials. Namral fibres are extracted from various parts of plants, and several extraction procedures are in vogue. The fibre properties depend on the part of the plant from which the fibres are obtained and the extraction methods used. 

In choosing a solvent for the extraction of bioactives, the ability to extract components has to be considered. For instance, ionic solutes can be extracted from aqueous solvents. The general features of the bioactive molecule that are helpful to ascertain the isolation process include partition coefficient, acid-base properties, chaige, stability, and molecular size. In literature, many basic extraction procedures are available [2], Solvent choice for the extraction is a critical step. Single solvent is unlikely to extract all groups of bioactive compounds from the natural plant materials. In most of the cases, these methods will be refined to our requirements in terms of plant materials and solutes of our interest. The expected outcome from this extraction process should be high purity product, adequate quantity of bioactive compound, and confirming the stereochemistry of the molecule. 

Details of the extraction methods for ficine (4) and isoficine (5) were not given. Phyllospadine (6) was isolated from the flavonoid-containing n-butanol-soluble extract from dried plant material (4). The alkaloids from Vochysia and Buchenavia were isolated by conventional procedures, utilizing acid-base extraction and subsequent column or thin-layer chromatography using silica gel or alumina (5,6). 

Various plant extracts are allowed under most organic guidelines, provided that they are not formulated in petroleum-based synergists or carriers. However, they are only rarely used, primarily as insecticides (Table 4.1). Compost extracts are used more frequently, and are commercially formulated these days (Litterick ef al. 2004). They can be very effective in disease control, depending on the starting material, the composting and fermentation procedures, and the final microbial activity. 

The winning of the alkaloids is generally achieved by the usual procedures modified to suit the plant source and the properties of the bases. Pais el al. 17), when working with Panda oleosa, moistened the dried and ground plant material with 10% aqueous ammonia and 1% aqueous sodium carbonate followed by extraction with ether. The concentrated extract was shaken with aqueous amidosulfonic acid and the bases regenerated from the aqueous phase by ammonia. An ether solution of the liberated bases frequently yields crystals upon standing but these are virtually always a mixture of bases. 

Scutianine-A was obtained from a methanol extract of the ground plant. The somewhat concentrated extract was diluted with water, basified with ammonia to pH 8, and exhausted with benzene. The alkaloids were removed from the benzene extract by means of 5% aqueous citric acid. The bases, regenerated from the aqueous phase, were recovered with chloroform or methylene chloride (18). This procedure is recommended when large amounts of plant material are available. 

A further simplification has been reported (27) in which the dried plant material is extracted with three times its volume of a mixture of benzene, concentrated aqueous ammonia, and methanol in the ratio 100 1 1, respectively. Some five successive extractions appear to be adequate. The bases are separated from the combined benzene extract by shaking with 6% aqueous citric acid. The troublesome emulsions that are encountered in other procedures are largely avoided by this method. 

The element is extractable from strong hydrochloric acid solutions into 4-methylpentan-2-one. This approach may be applied to the analysis of plant material, if the ash is extracted with the strong hydrochloric acid required.35 Kim et al.36 masked iron(m) by reduction to iron(n) with tin(n) chloride before extracting molybdenum as its thiocyanate complex with Aliquat 336 into chloroform. The latter was evaporated, and the residue extracted with 4-methylpentan-2-one prior to determination of molybdenum by AAS. The procedure was applied to soils, sediments, and natural waters. In fertilizer analysis, the thiocyanate complex of molybdenum has been extracted, after reduction of iron with tin(n) chloride, into 3-methylbutan-l-ol, and the latter extract analysed directly.37 In another thiocyanate-based procedure, total molybdenum from soils and geological materials was extracted into 4-methyl-pentan-2-one.38... 

A.L.D. Comitre, B.F. Reis, Automatic flow procedure based on multicommutation exploiting liquid—liquid extraction for spectrophotometric lead determination in plant material, Talanta 65 (2005) 846. 

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