Extraction of phenolics
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Transcript of Extraction of phenolics
ASSIGNMENT OF PLANT
PHYSIOLOGY
Aqsa Khalil
Topic:Extraction of Phenolics from Plant
Material:
What are Phenolics?
Phenolic are aromatic benzene ring compounds with one or more hydroxyl groups produced by plants mainly for protection against stress.
Plant Phenolics:• Broadly distributed in plant kingdom.• Most abundant secondary metabolites of
plants.• Comprise 40% soluble protein of plants.• More than 8000 structures of phenolics
are known.• Lignin(polyphenol) is second most
abundant compound in plant.
Sources of Phenolics:• Fruits• Vegetables• Cereals• Olive• Legumes• Chocolate• Tea• Coffee• Wine
Classification of Phenolics:
Types of Phenols:• Simple Phenols: Coumarins Phenolic acids Hydroxybenzoic acids Hydroxycinnamic acids.• Polyphnols Tannins Lignins Flavenoids
Different Methods of Extraction:
There are different methods of extraction of phenolics from plant materials,•Conventional method•Soxhlet Extraction•Ultrasound Assisted Extraction(UAE)•Microwave Assisted Extraction(MAE)•Ultrasound/Microwave Assisted Extraction (UMAE)
1-Conventional Method of Extraction:
• Extract 5g of homogenized material with 50ml of appropriate solvent.
• Continue magnetic stirring(magnetic size 4.0-5.0cm) at 700rpm for 1hr at room temperature.
• The extract was then filtered(paper no.89)• Do the extraction process in triplicate.
2-Soxhlet Extraction:• Finely ground crude drug is placed in a
porous bag or “thimble” made of strong filter paper, of the Soxhlet apparatus.
• Heat the extracting solvent and condense it in a condenser.
• The condensed extractant drips into the thimble containing the crude drug, and extracts it by contact.
• When the level of liquid in chamber rises to the top of siphon tube , the liquid contents of chamber siphon is put into flask.
• This process is continuous and is carried out until a drop of solvent from the siphon tube does not leave residue when evaporated.
Soxhlet Apparatus
3-Sonication:• The procedure involves the use of
ultrasound with frequencies ranging from 20 kHz to 2000 kHz.
• An appropriate solvent is mixed with a sample and sonicated under controlled temperature for a specified time.
• This increases the permeability of cell walls and produces cavitation hereby releasing cell contents.
Probe and Bath Sonicators:• Probe sonicators are constantly in contact
with the sample and make reproducibility and repeatability difficult. In addition, the risk of sample contamination and foam production is higher.
• Bath sonicators can act on a range of samples simultaneously and allow for higher reproducibility
Example:• Extraction of isoflevones from Soy Beans
by sonication has done with 40%-60% Ethanol for 20 min.
• The yield was 1.353(mg GAE b/g) .
Probe and Bath Soncators:
Bath Sonicators: Probe Sonicators:
4-Microwave Assisted Extraction:
• Microwaves are non-ionizing radiation• (frequencies between 300 MHz and 300
GHz).• They induce molecular motion in materials or
solvents with dipoles resulting in sample heating .
• The heating causes plant cells to lose moisture through evaporation; swells and eventually ruptures the cells, releasing their active components.
Procedure:• Make 80%v/v solution of ethanol.• Take 10-40ml of solvent per g palnt
material.• Irradiate the solution for 5-30min at 70–130
°C and 200–1000 W microwave power.• The results revealed that MAE has the
power to give the highest yield compared to other methods
Example:• The extraction of polyphenols from Tea
was done using 12ml of 60% Ethanol per g of tea material for 10 min at 80°C using 600W microwave radiation.
Microwave Apparatus:
5-Ultrasound/Microwave Assisted Extraction (UMAE)
• The coupling of two powerful radiation techniques (ultrasonic and microwave).
• It consume lower volumes of solvents and result in higher extraction yields than conventional extraction.
• Lou et al. applied microwaves with ultrasonic extraction (UAME) and maceration to extract phenolics from Burdock leaves. The final optimized UMAE method gave a phenolic yield of 9 mg/g while less than 0.5 mg/g was achieved using maceration.
UMAE Apparatus:
6-Supercritical Fluid Extraction (SFE)
• Supercritical Fluid Extraction (SFE) is the process of separating one component (the extractant) from another (the matrix) using supercritical fluids as the extracting solvent. Extraction is usually from a solid matrix, but can also be from liquids.
• A SCF is a type of solvent that forms when the temperature and pressure of the fluid increase above its critical point .
• The SCF generated has the penetration power of the gas form and density of the liquid form.
• The usual SCF applied in SFE are methane, carbon dioxide, ethane, propane, ammonia, ethanol, benzene and water.
• Cylindrical extraction vessels are used.• The collection of the extracted analyte from
SFE is another important method. Significant analyte can lost during this step.
• CO2 is used as extracting solvent.• Organic solvents are frequently added to
CO2 extracting fluid to alleviate the polarity limitations.
• The component recovery rate generally increased with increase in temperature and pressure,
• For example the extraction of phenolic contents from guava seed through SFE is done at 50°C with at pressure of 200-300bar for120min using Ethyl acetate and Ethanol as modifier solvent with CO2.
SFE Apparatus:
7-Subcritical Water Extraction (SCWE)
• Water becomes subcritical when the temperature is 100–347 °C applied under sufficient pressure (normally 10–60 bar) to preserve its liquid form .
• The dielectric constant of water reduces under subcritical conditions due to the breakdown of intermolecular hydrogen bonds.
• At these subcritical conditions water shows polarity and dielectric constant equal to organic solvents like ethanol and methanol.
• For extraction of anthraquinones from Morinda citrifolia, the effectiveness of SCWE compared to that of other extraction methods, such as ethanol extraction in a stirred vessel.
Example:• Extraction of phenolic compound from Rice
bran through SCWE is done at 120-200°C for 5min at a pressure of 20bar using 2.5ml of solvent per gram material.
• SCWE extracts gave almost the same antioxidant activity as Soxhlet extracts, but SCWE extracts contained higher antioxidant activity than ethanol extracts and ultrasound-assisted extracts
SCWE Apparatus:• SCWE could be a
good alternative industrial method to use for extraction of large amounts of phenolic compounds without toxic organic solvent residues.
8-High Hydrostatic Pressure Extraction (HHPE)
• This method utilizes non-thermal super-high hydraulic pressure (1,000–8,000 bar).
• It works on the basis of mass transport phenomena.
• The pressure applied increases plant cell permeability.
• The cell components diffuse under applied pressure.
• HHPE creates pressure difference b/w the cell membrane interior and exterior.
• It allows solvent to penetrate into the cell causing leakage of cell components.
Example:• A higher yield of soluble polyphenols
in the juice of cashew apples has been obtained
using HHPE compared to other methods
HHPE Apparatus:
Importance:• Involved in defense against insect, herbivores and fungi.• Some have allelopathic function (Caffeic acid & ferulic acid).• Some are pigments and give color to plant parts
(anthocyanins).• Act as antiflamatory and antioxidant(blue anthocyanins).• Provide protection against UV(flavones & flavonles).• Antimicrobial properties and also involved in signaling
(isoflavonoids).• In humans phenolic compounds do not allow constriction of
blood vessels (tannins in tea& caffeine).
.