Dear Vinesh Kumar

How do we know what are all the constituents a plant contains, in which form or complex and in what percentage? Your question can be appropriately answered provided we have a standard to compare. If a single solvent can extract or isolate all the constituents of the plants, then there will not be any need to test several solvents under diverse conditions (which means we need several solvents to extract different constituents with the hope these solvents are not changing the chemical structure or nature of the constituent). It is known at least in aromatic plants that during distillation the process conditions produce artifacts. Similarly when you are extracting a fresh or semi-dried or dried plant parts, the physiology of that plant part would have certainly undergone several changes. A living plant tissue is different from the dead and dried sample. In a living plant it is known that the number, nature and concentration of both primary and secondary metabolites undergo changes depending on the plant's requirement and the stresses [ abiotic (temperature, wind, moisture/ drought, salt, nutrient etc.) and biotic (pests and diseases)] the plant experiences from time to time.

Good luck.

An alkaline solvent such as aqueous NaOH (used to eaxtract cell wall polysaccharides) can hydrolyse ester and amide bonds. Solvents such as 70% ethanol, ethyl acetate or diethyl ether are inert, however.

Yes I think solvents could affect  or degrade certain plants constituents. I think if you used general solvent such as methanol, ethyl acetate, CH2Cl2, hexane etc, most of the constituent are stable in room temperature.. If you know  chemical constituents that you are wanted to extract,, it will be easier to select the solvents.

Dear Friends

Very informative answers. Is there any method(s) by which we can isolate and identify all the constituents of a plant? How can we ensure that what we have extracted or isolated is what the plant contains?

Follow this thread:

https://www.researchgate.net/post/What_is_the_maximum_number_of_compounds_an_essential_oil_can_contain

Hi everyone,

Subject: Hydrophobic compounds, carotenoid extraction. Extraction of organic molecules from plant or human tisue is a complex process. For example, in  papers [2,3] we were intreseted to check the # of carotenoids in fruits,  vegetables and  thhe same in human plasma. We also did study  the effect of food preparation on the catenoid composition. The carotenoids are hydrophobic and hence most of the time hexane and THF were used as exttaction solvents. After google search I have found, recently,  other autors [1] have used diethyl ether: chloroform (1:2), methanol: chloroform: dichloromethane (1:2:1), methanol: chloroform: acetone (1:2:1) and dichloromethane: chloroform (1:2)  In early year 1990,  there was a feeling there were 6 to 8 carotenoids in human plasma. Early break through in our lab came after using HPLC techniques. [2,3]. We were excited to see couple of oxidation products carotenoids in human plasma ( Total carotenoids ~15). That means they were the metabolites. We are glad to see that there is more intesest in fruits and vegetables. One can can not under estimate the usefulness of god given  any  natural products in human diet. A bowl of (100 grams) any green,yellow,red fruits and vegetables can lower the risk of  constipation (fiber) and apparently even cancer (anti oxidants). There are 1pp  of papers!  now on carotenoids in various human tissues  Fruits tend to have more esters in them. I hope it helps a few of you

[1]     Prateek Gupta, Yellamaraju Sreelakshmi* and Rameshwar Sharma*  2015

A rapid and sensitive method for determination of carotenoids in plant tissues by high performance liquid chromatography. Plant Methods  11:5    doi:10.1186/s13007-015-0051-0,

http://www.plantmethods.com/content/11/1/5

[2]     Frederick Khachik, Gary R. Beecher, and Mudlagiri B. Goli  1991 Separation, identification, and quantification of carotenoids in fruits, vegetables and human plasma by high performance liquid chromatography. 1991  Pure & Appl. Chem., 63, 71-80.

 http://www.iupac.org/publications/pac/1991/pdf/6301x0071.pdf

[3]     Khachik F1, Beecher GR, Goli MB, Lusby WR, Smith JC Jr. 1992.  Separation and identification of carotenoids and their oxidation products in the extracts of human plasma. Anal Chem. 1992 Sep 15;64(18):2111-2122. DOI: 10.1021/ac00042a016

Check this informative link:

http://www.slideshare.net/rahulbs89/extraction-of-plant-contituents