Why do some people use fractionation ( n-hexan ,chloroform ,ethylacetate and butanol etc) not crude ?. Does fractionation contain phenols alone?
Dear
This depends upon the aims and nature of your study. We do extractions with solvents like Methanol, Ethanol etc having high extraction power. So you have a lot of phyto-chemicals there in the crude extract, and the activity might be just for the fraction of the extract. Therefore, we do fractionation check to out weather the polar or non polar portion of the extract is eliciting the antioxidant or whatever the activity might be under study.
You can then go for Column Chromatography to isolate the bio-active compounds.
Thanks
Dr. Izhar Ahmad
Fractinations need to seperate the compunds based on their polarity. So we could determine which one fraction with the strongest Antioxidant activity.
Phenolic compounds such as gallic acid, rutin and catechin are responsible for antioxidant activity as these compounds donate hydrogen atom or chelate metals which results in interruption of chain oxidation reactions. Polar solvent extracts may contain of phytochemicals responsible for good antioxidant potentials as compared to non-polar solvent extracts. Use of different polarity solvents can accumulate compounds responsible for antioxidant activity and can narrow down the isolation of compounds responsible for antioxidant or any other pharmacological activity.
The crude extract (e.g., in methanol) generally consists of a wide variety of chemical compounds differing in polarity. The fractionation allows us to separate the crude extract into different fractions based on polarity. The process is called sequential fractionation. That is, it is done in a sequence, starting with a least polar solvent (such as, hexane) and gradually moving towards higher polarity ones, such as chloroform/DCM, ethyl acetate and n-butanol.
- Badges
- Science topic
- Similar topics
- Chemistry, Organic
- Organic