Pharmacognosy Non-conventional extraction techniques part 2.pdf

pharmacognosy‫‏‬ Non-conventional extraction techniques Part 2 Non-conventional extraction techniques Content: Pulsed-electric field extraction (PEF) 3 Pressurized liquid extraction (PLE) 11 Supercritical fluid extraction (SFE) 18 Pulsed-electric field extraction (PEF) Pulsed-electric field extracti...

pharmacognosy‫‏‬ Non-conventional extraction techniques Part 2 Non-conventional extraction techniques Content: Pulsed-electric field extraction (PEF) 3 Pressurized liquid extraction (PLE) 11 Supercritical fluid extraction (SFE) 18 Pulsed-electric field extraction (PEF) Pulsed-electric field extraction (PEF) The pulsed electric field (PEF) treatment was found to be useful for improving the pressing, drying, extraction, and diffusion processes during the last decade. The principle of PEF is to destroy cell membrane structure for increasing extraction. Pulsed-electric field extraction (PEF) During suspension of a living cell in electric field, an electric potential passes through the membrane of that cell and based on the dipole nature of membrane molecules, electric potential separates molecules according to their charge in the cell membrane. After exceeding a critical value of approximately 1 V of transmembrane potential, repulsion occurs between the charge carrying molecules that form pores in weak areas of the membrane and causes drastic increase of permeability. Pulsed-electric field extraction (PEF) Usually, a simple circuit with exponential decay pulses is used for PEF treatment of plant materials. It has a treatment chamber consisting of two electrodes where plant materials are placed. Pulsed-electric field extraction (PEF) The effectiveness of PEF treatment strictly depends on the process parameters, including : 1. field strength 2. specific energy input 3. pulse number 4. temperature 5. properties of the material. PEF can increase mass transfer during extraction by destroying membrane structure of plant materials for enhancing extraction and decreasing extraction time. Pulsed-electric field extraction (PEF) PEF has been applied to improve release of intracellular compounds from plant tissue with the help of increasing cell membrane permeability. PEF treatment at a moderate electric field is found to damage cell membrane of plant tissue with little temperature increase and for this reason, PEF can minimize the degradation of heat sensitive compounds. PEF is also applicable on plant materials as a pretreatment process prior to conventional extraction to lower extraction effort. Pulsed-electric field extraction (PEF) PEF treatment for extraction of betanin from beetroots showed highest degree of extraction compared with freezing and mechanical pressing. The recovery of phytosterols from maize increased by 32.4% and isoflavonoids (genistein and daidzein) from soybeans increased by 20–21% when PEF was used as pretreatment process. Pulsed-electric field extraction (PEF) Bioactive compounds such as anthocyanins were extracted from grape by-product using various techniques and found better extraction of anthocyanin monoglucosides by PEF. The application of a PEF treatment on grape skin before maceration step can reduce the duration of maceration and improve the stability of bioactives (anthocyanin and polyphenols). Pressurized liquid extraction (PLE) Pressurized liquid extraction (PLE) Pressurized liquid extraction (PLE) In 1996, Richter et al. first described PLE. This method is now known by several names; pressurized fluid extraction (PFE), accelerated solvent extraction (ASE), enhanced solvent extraction (ESE), and high pressure solvent extraction (HPSE). The concept of PLE is the application of high pressure to remain solvent liquid beyond their normal boiling point. Pressurized liquid extraction (PLE) High pressure facilitates the extraction process. Automation techniques are the main reason for the greater development of PLE-based techniques along with the decreased extraction time and solvents requirement. PLE technique requires small amounts of solvents because of the combination of high pressure and temperatures which provides faster extraction. Pressurized liquid extraction (PLE) The higher extraction temperature can promote higher analyte solubility by increasing both solubility and mass transfer rate and, also decrease the viscosity and surface tension of solvents, thus improving extraction rate. In comparison to the traditional soxhlet extraction PLE was found to dramatically decrease time consumption and solvent use. Now a days, for extraction of polar compounds, PLE is also considered as a potential alternative technique to supercritical fluid extraction. Pressurized liquid extraction (PLE) PLE is also useful for the extraction of organic pollutants from environmental matrices those are stable at high temperatures. PLE has also been used for the extraction of bioactive compounds from marine sponges. Applications of PLE technique for obtaining natural products are frequently available in literature. Pressurized liquid extraction (PLE) Additionally, due to small amount organic solvent use PLE gets broad reorganization as a green extraction technique. PLE has been successfully applied to extract bioactive compounds from different plant materials. Using optimized condition isoflavones were extracted from soybeans (freeze-dried) without degradation by PLE. Pressurized liquid extraction (PLE) Comparing of PLE, for the extraction of terpenoids and sterols from tobacco, with Soxhlet extraction and ultrasonically assisted extraction; in consideration of yield, reproducibility, extraction time, and solvent consumption, PLE has been considered as an alternate to conventional methods due to faster process and lower solvent use. Flavonoids extracted from spinach by PLE using a mixture of ethanol and water (70:30) solvent at 50–150 °C were more effective than water solvent at 50–130 °C. Supercritical fluid extraction (SFE) Supercritical fluid extraction (SFE) Supercritical fluid extraction (SFE) The application of supercritical fluid for extraction purposes started with its discovery by Hannay and Hogarth (1879) but the credit should also be given to Zosel who presented a patent for decaffeination of coffee using SFE (Zosel, 1964). Since this beginning, supercritical fluid technique has attracted wide scientific interest and it was successfully used in environmental, pharmaceutical and polymer applications and food analysis. Supercritical fluid extraction (SFE) Several industries have been using this technique for many years, especially, decaffeinated coffee preparation industries Every earthly substance has three basic states namely: Solid, Liquid and Gas. Supercritical state is a distinctive state and can only be attained if a substance is subjected to temperature and pressure beyond its critical point. Supercritical fluid extraction (SFE) Critical point is defined as the characteristic temperature (Tc) and pressure (Pc) above which distinctive gas and liquid phases do not exist. In supercritical state, the specific properties of gas and/or liquid become vanish, which means supercritical fluid cannot be liquefied by modifying temperature and pressure. Supercritical fluid extraction (SFE) Supercritical fluid possesses gaslike properties of diffusion, viscosity, and surface tension, and liquid-like density and solvation power. These properties make it suitable for extracting compounds in a short time with higher yields. Supercritical fluid extraction (SFE) A basic SFE system consists of the following parts: 1. tank of mobile phase, usually CO2 2. pump to pressurize the gas 3. co-solvent vessel and pump 4. an oven that contains the extraction vessel 5. a controller to maintain the high pressure inside the system and a trapping vessel. 6. Usually different type of meters like flow meter, dry/wet gas meter could be attached to the system. Supercritical fluid extraction (SFE) Carbon dioxide is considered as an ideal solvent for SFE. The critical temperature of CO2 (31 °C) is close to room temperature, and the low critical pressure (74 bars) offers the possibility to operate at moderate pressures, generally between 100 and 450 bar. Supercritical fluid extraction (SFE) The only drawback of carbon dioxide is its low polarity which makes it ideal for lipid, fat and nonpolar substance, but unsuitable for most pharmaceuticals and drug samples. The limitation of low polarity of carbon dioxide has been successfully overcomed by the use of chemical modifier. Usually a small amount of modifier is considered as useful to significantly enhance the polarity of carbon dioxide. Supercritical fluid extraction (SFE) For example, 0.5 ml of Dichloromethane (CH2Cl2 ) can enhance the extraction which is same for 4 h hydrodistillation. The properties of sample and targeted compounds and the previous experimental result are main basis for selection of the best modifier. The successful extraction of bioactive compounds from plant materials rely upon several parameter of SFE and most importantly these parameter are tunable. Supercritical fluid extraction (SFE) These parameter need to be precisely controlled for maximizing benefits from this technique. The major variables influencing the extraction efficiency are temperature, pressure, particle size and moisture content of feed material, time of extraction, flow rate of CO2 , and solvent-to feed-ratio. Supercritical fluid extraction (SFE) The advantages of using supercritical fluids for the extraction of bioactive compounds can be understood considering the following points: 1. The supercritical fluid has a higher diffusion coefficient and lower viscosity and surface tension than a liquid solvent, leading to more penetration to sample matrix and favorable mass transfer. Extraction time can be reduced substantially by SFE in compared with conventional methods. 2. The repeated reflux of supercritical fluid to the sample provides complete extraction. Supercritical fluid extraction (SFE) 3. The selectivity of supercritical fluid is higher than liquid solvent as its solvation power can be tuned either by changing temperature and/or pressure. 4. Separation of solute from solvent in conventional extraction process can easily be bypassed by depressurization of supercritical fluid, which will save time. 5. SFE is operated at room temperature, so an ideal method for thermo labile compound extraction. Supercritical fluid extraction (SFE) 6. In SFE, small amount of sample can be extracted compared with solvent extraction methods which will save time for overall experiment. 7. SFE uses little amount of organic solvent and considered as environment friendly. 8. On-line coupling of SFE with chromatographic process is possible which is useful for highly volatile compounds. Supercritical fluid extraction (SFE) 9. The recycling and reuse of supercritical fluid is possible and thus minimizing waste generation. 10. SFE scale can be arranged on specific purpose from few milligram samples in laboratory to tons of sample in industries. 11. SFE process provides information regarding extraction process and mechanism which can be manipulated to optimize extraction process. Supercritical fluid extraction (SFE) Supercritical CO2 modified with ethanol (15 wt.%) gave higher extraction yields of naringin (flavonoid) from citrus paradise than pure supercritical carbon dioxide. Polyphenols and procyanidins were extracted from grape seeds using SFE, where methanol was used as modifier and methanol modified CO2 (40%) released more than 79% of catechin and epicatechin from grape seed. Optimized condition of SFE was used to extract indole alkaloids from Catharanthus roseus leaves and best recoveries were obtained for catharanthine using 6.6% methanol as modifier for 40 min.