Lecture 9: Polyphenols Flashcards
What are polyphenols and why are they important?
WHAT: a secondary metabolite of plants that are formed by a benzene ring
WHY: they have antioxidant roles and have a role in prevention and treatment of many diseases, they are being used as food additves for health benefit, flavour and preservation
what are the roles of phenolic compounds
- pigmentation in plants
- protection for plants agaisnt insects and pathogens
- antioxidant (redox properties let them absorb and neautrilze free radicals)
- antibacertial
- anticarinogrenic
- antiinflamotory
why is analysing polyphenols in food important for the food industry?
- for standarization (organoleptic properties grading, nutrional quality→ price)
- tracing the geographical and genetic orgin of the product (quality)
what are the three traditional extraction methods and what are some modern techniques?
- soxhlet extraction
- maceration
- hydrodistilation
modern: ultrasound, microwave, liquid pressure extraction (LPE), supercritical fluid extraction
What are the disadvantages of conventional techinques and what are the advantages of modern techniques?
Disadvantages:
- large volumes of solvent
- long extraction period
- risk of oxidation of extracted bioactive compounds
Advantages:
- speed
- selectivity
- low volume solvent
- increased extraction efficiency
describe the Maceration extraction method
- leave plant material in solvent to extract soluble molucules then filter and evaporate
-advantages include it is inexpensive, uses solvent mixture, can control temperatures and maintain heat sensitive molcules
describe the soxhelt extraction method
Sample Preparation:
Grind or finely chop the solid sample containing polyphenols.
Extraction Setup:
Place the sample in a thimble made of filter paper.
Insert the thimble into the Soxhlet extraction apparatus.
Solvent Selection:
Choose a suitable solvent for polyphenol extraction (commonly ethanol or methanol).
Cyclic Extraction:
The solvent is heated and vaporized, then condensed and allowed to drip onto the sample.
This cycle continues, allowing the solvent to extract polyphenols from the sample.
Siphoning Process:
The condensed solvent with dissolved polyphenols is siphoned back into the flask.
Continuous Extraction:
The cyclic extraction process is repeated until the polyphenols are thoroughly extracted from the sample.
Evaporation:
Separate the solvent from the polyphenols by evaporating it, typically using a rotary evaporator.
Polyphenol Measurement:
Measure the concentration of polyphenols in the collected extract.
This can be done using various analytical techniques, such as spectrophotometry or chromatography
what are the advantages and disadvantages of the soxhelt method?
-ADVANTAGES: fast contact between solvent and sample with better material transfer and no filtration step -DISADVANTAGE: time consuming, uses a lot of solvent and energy, high temperature for long time which can cause degradation
Describe the steps of the hydrodistillation method of extraction
Prepare the Plant Material:
Cut or grind plant parts like leaves or flowers.
Add Water and Heat
Put the plant material in a setup and add water.
Heat it to make steam.
Steam Extraction:
Steam passes through the plant, extracting polyphenols.
Collect the Extract:
Condense the steam back into liquid, collecting a mixture of essential oil and water with polyphenols.
Separation:
Separate the essential oil from the water part.
Polyphenol Extraction:
Focus on the water part to extract polyphenols.
Concentration:
Increase the concentration of polyphenols in the extract. -used for getting bioactive
What is the hydrodistilation method of extraction used for and what are its disadvantages?
used for getting bioactive molecules and essential oils
- DISADVANTAGE: extracted at high temperature so volatile compounds can be lost
Describe the modern extraction method ultrasonic extraction
- uses mechanical wavs that can move so when it makes its way through the liquid the oscilations of the molecule results in areas of compression and depression which forms bubbles
- these bubbles burts near the plant cells
- this realses molecules
- these bubbles burts near the plant cells
describe the folin-ciocalteu method of determining total polyphenols
- use of folin-ciocalteu reagent to oxidize all polyphenols
- reagent which is made of two acids is reduced during the oxidation in a mixture of blue oxides of tungsten
- blue color that is absorbed is proprotional to the level of phenolic compounds
in determination of polyphenols give an example of an indirect and direct way of measuring
indirect: using spechtrometirc assay with enxyme perioxidase to determine antixodiant activity based on the amount of polyphenols
direct: using high performance liquid chromatagaraphy to quantify chemical molecules
