Plants Soxhlet extraction

Miscellaneous Plants Soxhlet extraction Study of extraction conditions - [77]... 

Extraction of residues from soil samples is much more difficult than their extraction from plant or water samples. The pesticide residues in the soil exist often in several forms as bound residue , which may affect the extraction efficiency of pesticides from the soil. Then, various extraction methods such as organic solvent extraction, Soxhlet extraction, sonication extraction, microwave dissolution and supercritical fluid extraction (SEE) are used. Some extraction methods are described in the following. 

In other isolation methods, where the ccmpound(s) was removed from the donor plants, the plant material was either dried or macerated prior to cold and hot water treatment. Soxhlet-type extraction was employed when organic solvents were used. Leaves and stems from the intact plants were extracted to collect the suspected volatile substances and those chemicals likely to be released by rain, mist... 

Histamine Extraction. Some secondary plant metabolites are very difficult to extract from their natural matrix and require lengthly soxhlet extractions. Complete histamine extraction was relatively simple. The HPLC separation was used to design a technique to confirm a complete extraction. The histamine peaks from three serial extractions on the same 3 grams of cotton plant leaves are shown in Figure 6. Post-column fluorescence detection of the fourth extraction showed only the slightest response even at the highest detector amplitude. Three extractions accounted for from 95% to 99% of the histamine content. The plant residues from these extractions yielded no additional histamine after standing at ambient conditions for two weeks. 

Extraction. Each dried plant part was Soxhlet-extracted with petroleum ether. The solvent was evaporated vacuo to give a residue labeled Fraction A (Scheme I). The marc was air-dried and extracted with ethanol in a Soxhlet apparatus. Evaporation of the solvent vacuo yielded Fraction B. The aqueous phase was removed by freeze-drying and the water-soluble residue was labeled Fraction C. 

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). " ... 

Microwave-assisted extractions (MAE) can be performed in open (focused MAE) or closed (pressurized MAE) flasks. This technique is commonly used for extractions from complex and difficult sample matrices, replacing time- and solvent-intensive Soxhlet extractions or hydrodistillations.46 MAE is also widely applied to environmental samples, for example, for extracting polycyclic aromatic hydrocarbons (PAH) from soil, methylmercury from sediments, and trace metals and pesticide residues from plant material47 48 The use of microwave treatment instead of hydrodistillation offers a solvent-free separation technique essential oils are heated and dry-distilled 46... 

Like Soxhlet, sonication is also recognized as an established conventional method, although it is not as widely used. Limited research has focused on sonication per se or its comparison with Soxhlet. Qu et al. [13] developed a method using sonication with methanol for the extraction of linear alkylbenzene sulfonate (LAS) in plant tissues (rice stems and leaves). Both efficiency and accuracy were found to be high. The mean recovery was 89% (84 to 93% for LAS concentration of 1 to 100 mg/kg), and the relative standard deviation (RSD) was 3% for six replicate analyses. Its advantages over Soxhlet extraction were speed (1 hour), less solvent consumption, and smaller sample requirement (2 to 3 g). 

Different plants including spearmint (Mentha spicata L ), rosemary (Rosmarinus officinalis L.), dill (Anethum graveolens L.), clary sage (Salvia sclarea L.) and chamomile (Matricaria chamomilla L.) were extracted with CO2 in a high pressure apparatus with 5 L extractor vessel volume. Fractionation of extracts was carried out by releasing the separation pressure at two stages. The extracts were separated into essential oil rich oil and fatty/waxy products. The extracts were collected as separate samples successively in time. The extraction with carbon dioxide was compared to conventional steam distillation (essential oils) and to Soxhlet extraction with hexane (fatty oils). 

Standard methods were used for the determination of moisture, essential oil (hydrodistillation) and oleoresin (hexane Soxhlet extraction) content of the raw and residual plant materials. The moisture content and yields obtained by different extraction methods are given in Table 1. Volatile oil contents of the fractionated extracts were also determined by steam distillation. The analysis of particle size distribution was performed by passing the ground plant material through sieves of various mesh size and weighing the fraction taken from each tray. 

The increasing risks to human health posed by the widespread use of pesticides in our environment is well established [212,213]. Thus, the determination of pesticides in water, plants, soil, sediments, foodstuff, etc., is of major concern today [214,215]. Microwave-assisted extraction provides an efficient, reproducible alternative to classical methods based on Soxhlet extraction or sonication for the extraction of pesticides from environmental samples. 

The commonly used method is the Soxhlet-Extraction by using diethylether and/or pentane as solvent. The sample is extracted continuously by using an Soxhlet-extrac-tor over a period of several hours. The extract is dried and concentrated by evaporation of the solvent. The residual extract can be applied directly to GC-analysis. This method is used for solid or pasty flavourings as well as for whole fruits or plants and their parts where the composition of the volatile compounds is required [4],... 

In an analysis of B[a]P and coal tar pitch volatiles in workplace air conducted by Ny et al. (1993), urine samples were analyzed for the pyrene metabolite 1-hydroxypyrene, and a high correlation between levels of this biomarker and PAH air levels was observed. Analyses were also conducted by HPLC with fluorescence detection. Tolos et al. (1990) reported results of 1-hydroxypyrene urinalysis for aluminum reduction plant workers, and showed a strong positive correlation between the compound and 17 environmental PAHs. This work verified the choice by earlier researchers (Jongeneelen et al. 1988) of the pyrene metabolite as a useful marker of exposure to PAHs. Elovaara et al. (1995) also demonstrated the usefulness of 1-hydroxypyrene as a biomarker for exposure to naphthalene and 10 other PAHs for creosote impregnation plant workers. Particulate PAHs were Soxhlet extracted with cyclohexane and analyzed by HPLC with fluorescence detection. 

Extraction of the plant materials was performed in a flow apparatus similar to that described in chapter 4. The current National Cancer Institute protocol for extracting new plant materials consists of Soxhlet extraction with 95% ethanol. (For comparison purposes a Soxhlet extraction was also done for this study.) Carbon dioxide conditions of 275 bar and 35°C were chosen to achieve a high density at a temperature reasonably close to ambient temperature. About 20 g of plant material were used for each extraction. The material was contacted with 200 standard liters of carbon dioxide in a flow extractor, and the extract that was collected when the carbon dioxide was expanded to ambient pressure was tested in a bioassay test. 

As a consequence of the toxicity related to the presence of aristolochic acid in plant preparations, several health institutions, such as the US Food and Drug Administration, Therapeutic Goods Administration have recently published safety information to prevent further cases of intoxication (information available at web address http //www.cfsan.fda. gov/ dms/ds-bot.html) [471], So detecting aristolochic acids in plant species that could be used in herbal remedies, and also in herbal preparations of uncertain composition, has attracted great priority in recent years to help prevent future adverse reactions. Aristolochic acids present in medicinal plants or herbs are analyzed by soxhlet extraction followed by TLC in the Chinese pharmacopoeia [412]. Another report used multiple ultrasonic extraction followed by HPLC analysis [472]. Ong s laboratory reported a method using a home made pressurized liquid extraction (PLE) system in dynamic mode to extract aristolochic acid in medicinal plants, followed by gradient elution HPLC [473]. Several scientific communities described various analytical methods for... 

Neither soxhlet extraction nor steam distillation is designed to isolate volatiles from solids for subsequent determination. Slurrying the solids in water and then applying the PaT procedure has been reported A vacuum extractor with cryogenic concentration has been applied to both fish and sediment samples for determination of volatile priority pollutants PaT, LLE, and static headspace techniques have all been applied to the determination of volatiles in sludges from municipal waste treatment plants... 

In the pharmaceutical field, PFE has also been used for two primary purposes, namely to extract pharmacologically active substances from plants and, especially, for quality control of tablets and medical foods. In this field, PFE clearly surpasses classical extraction methods such as those endorsed by pharmacopeias (which use as official standards techniques such as Soxhlet extraction, percolation, maceration, digestion, extraction under reflux, and steam distillation) and others based on ultrasonica-tion or turboextraction. PFE is a firm candidate for use in high-throughput screening programs for natural product discovery, where large numbers of small-scale extractions have to be performed in an efficient, reproducible manner. 

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