Pharmacognosy Non-conventional extraction techniques.pdf

pharmacognosy Non-conventional extraction techniques Non-conventional extraction techniques Content: Non-conventional extraction techniques 3 Ultrasound-assisted extraction (UAE) 8 Enzyme-assisted extraction (EAE) 17 Microwave assisted extraction (MAE) 22 Non-conventional extraction techniques Non-c...

pharmacognosy Non-conventional extraction techniques Non-conventional extraction techniques Content: Non-conventional extraction techniques 3 Ultrasound-assisted extraction (UAE) 8 Enzyme-assisted extraction (EAE) 17 Microwave assisted extraction (MAE) 22 Non-conventional extraction techniques Non-conventional extraction techniques The major challenges of conventional extraction methods are : 1. longer extraction time.  2. Requirement of costly and high purity solvents. 3. Evaporation of the huge amount of solvent.  4. Low extraction selectivity.  5. Thermal decomposition of the rmo labile compounds. Non-conventional extraction techniques To overcome these limitations of conventional extraction methods, new and promising extraction techniques are introduced. These techniques are referred to as non-conventional extraction techniques. Non-conventional extraction techniques Some of the most promising techniques are:  1. Ultrasound assisted extraction.  2. Enzyme-assisted extraction.  3. Microwave-assisted extraction.  4. Pulsed electric field assisted extraction. 5. Supercritical fluid extraction.  6. Pressurized liquid extraction. Some of these techniques are considered as "green techniques" as they comply with standards set by Environmental Protection Agency, USA. Non-conventional extraction techniques These include less hazardous chemical synthesis; designing safer chemicals, safe solvents auxiliaries, design for energy efficiency, use of renewable feedstock, reduce derivatives, catalysis, design to prevent degradation, atom economy, and time analysis for pollution prevention and inherently safer chemistry for the prevention of accident. Ultrasound-assisted extraction (UAE) Non-conventional extraction techniques Ultrasound-assisted extraction (UAE) Ultrasound is a special type of sound wave beyond human hearing. Usually, in chemistry it is 20 kHz to 100 MHz. Like other waves, it passes through a medium by creating compression and expansion. This process produces a phenomenon called cavitation, which means production, growth and collapse of bubbles. Non-conventional extraction techniques A large amount of energy can produce from the conversion of kinetic energy of motion into heating the contents of the bubble, bubbles have temperature about 5000 K, pressure 1000 atm and, heating and cooling rate above 1010 K/s. Based on this principle, UAE has been developed. Non-conventional extraction techniques Only liquid and liquid containing solid materials have cavitation effect. The main benefit of UAE can be observed in solid plant sample because ultrasound energy facilitates organic and inorganic compounds leaching from plant matrix. Non-conventional extraction techniques Probable mechanism is ultrasound intensification of mass transfer and accelerated access of solvent to cell materials of plant parts. The extraction mechanism by ultrasound involves two main types of physical phenomena: A. the diffusion across the cell wall. B. rinsing the contents of cell after breaking the walls. Non-conventional extraction techniques Moisture content of sample, milling degree, particle size and solvent are very important factors for obtaining efficient and effective extraction. Furthermore, temperature, pressure, frequency and time of sonication are the governing factors for the action of ultrasound. UAE have also been incorporated along with various classical techniques as they are reported to enhance the efficiency of a conventional system. Non-conventional extraction techniques In a solvent extraction unit, an ultrasound device is placed in an appropriate position to enhance the extraction efficiency. The advantages of UAE include reduction in extraction time, energy and use of solvent. Ultrasound energy for extraction also facilitates more effective mixing, faster energy transfer, reduced thermal gradients and extraction temperature, selective extraction, reduced equipment size, faster response to process extraction control, quick start-up, increased production and eliminates process steps. Non-conventional extraction techniques UAE is seemed to be an effective extraction technique for herbal plants. Authors found that ultrasound can improve the extraction yield depending on solvent use; for example, phenolic compounds such as rutin, naringin and kaempferol were extracted from strawberries by developing semiautomatic method based On ultrasounds. Non-conventional extraction techniques A better recovery of chlorogenic acid from Eucommia ulmodies was obtained by UAE than classical extraction techniques. Ionic liquid based UAE have been regarded as very effective for extracting three alkaloids (vindoline, catharanthine and vinblastine) from Catharanthus roseus. Enzyme-assisted extraction (EAE) Non-conventional extraction techniques Enzyme-assisted extraction (EAE) Some phytochemicals in the plant matrices are dispersed in cell cytoplasm and some compounds are retained in the polysaccharidelignin network by hydrogen or hydrophobic bonding, which are not accessible with a solvent in a routine extraction process. Enzymatic pre-treatment has been considered as a novel and an effective way to release bounded compounds and increase overall yield. Non-conventional extraction techniques The addition of specific enzymes like cellulase, a-amylase, and pectinase during extraction enhances recovery by breaking the cell wall and hydrolyzing the structural polysaccharides and lipid bodies There are two approaches for enzyme-assisted extraction: 1. enzyme-assisted aqueous extraction (EAAE) 2. enzyme-assisted cold pressing (EACP). Usually, EAAE methods have been developed mainly for the extraction of oils from various seeds Non-conventional extraction techniques In EACP technique, enzymes are used to hydrolyze the seed cell wall, because in this system polysaccharide-protein colloid is not available, which is obvious in EAAE. Various factors including enzyme composition and concentration, particle size of plant materials, solid to water ratio, and hydrolysis time are recognized as key factors for extraction. The moisture content of plant materials is also an important factor for enzymatic hydrolysis. Non-conventional extraction techniques The oil extracted by enzyme-assisted methods was found to contain higher amount of free fatty acids and phosphorus contents than traditional hexane-extracted oil The EAE is recognized as eco-friendly technology for extraction of bioactive compounds and oil because it uses water as solvent instead of organic chemicals Microwave assisted extraction (MAE) Non-conventional extraction techniques Microwave assisted extraction (MAE) The microwave-assisted extraction is also considered as a novel method for extracting soluble products into a fluid from a wide range of materials using microwave energy. Microwaves are electromagnetic fields in the frequency range from 300 MHz to 300 GHz. Non-conventional extraction techniques They are made up of two oscillating fields that are perpendicular such as electric field and magnetic field. The principle of heating using microwave is based upon its direct impacts on polar materials Electromagnetic energy is converted to heat following ionic conduction and dipole rotation mechanisms Non-conventional extraction techniques During ionic conduction mechanism hear is generated because of the resistance of medium to flow ion. On the other hand, ions keep their direction along field signs which change frequently. This frequent change of directions results in collision between molecules and consequently generates heat. Non-conventional extraction techniques The extraction mechanism of microwave-assisted extraction is supposed to involve three sequential steps including:  1. separation of solutes from active sites of sample matrix under increased temperature and pressure.  2. diffusion of solvent across sample matrix.  3. release of solutes from sample matrix to solvent. Non-conventional extraction techniques Several advantages of MAE including: 1. quicker heating for the extraction of bioactive substances from plant materials.  2. reduced thermal gradients. 3. reduced equipment size. 4. increased extract yield. MAE can extract bioactive compounds more rapidly and a better recovery is possible than conventional extraction processes. Non-conventional extraction techniques It is a selective technique to extract organic and organometallic compounds that are more intact. MAE is also recognized as a green lechnology because it reduces the use of organic solvent. For polyphenols and caffeine extraction from green tea leaves, MAE achieved higher extraction yield at 4 min than any extraction methods at room temperature for 20 h. Non-conventional extraction techniques Ginsenosides extraction yield from ginseng root obtained by 15 min using MAE technique was better than conventional solvent extraction for 10 h. Also increased extraction efficiency of MAE by extracting silybinin from Silybum marianum compared with the conventional extraction techniques like Soxhlet and maceration.