Dear Researchers
Can I use NMR to identify type of phenolic compound inside the pitaya peel? so i just dry pitaya peel to remove water content by using freeze dryer and then blend the dried sample to get the powder form. after that Can i use NMR directly to identify type of phenolic compound on the powder sample ?
Hm... very interesting. I'd say, unless this is a special case where the peels are very rich in one type of that "phenolic ingredient" it would be only by a strike of luck that one can "identify" the structure. People who do isolation of novel Natural Products would have very little work if things were so simple.
One feature of phenols that can be perhaps useful during initial purification is that they often can be extracted into aqueous NaOH or KOH solutions. Other extractive operations may be necessary, which are normally followed by partitioning on solid phases (Si-gel chromatography, Sephadex, RP HPLC, etc). Analytical HPLC will assist you in assaying the fractions. But even after your component is isolated in a pure form, NMR work (1D-, 2D, nOe-based, etc) alone most probably will not be sufficient (again, unless you are dealing with a relatively simple and well know structure). Typically, HR MS or LCMS data will also be necessary (as Vladimir Khlebnikov indicated to you earlier), and in case of chiral compounds, optical rotation, CD, or chiral chromatography data should also be analyzed.
One perhaps tricky part of your question is that you want to "identify the type" of that compound. I presume that could mean that, for whatever reason, you do not actually need to precisely determine the structure. Perhaps in such case more direct NMR methods may provide some information?
Directly on the powdered sample, no. But if you soak it in suitable solvent and reconstitute in say HPLC grade DCM or ACN, dry it using rotavapor and you may then do the NMR using CDCl3. Hope this helps.
I doubt that NMR is an appropriate method for this type of analysis. Why don't use, for example, LC-MS ?
I would also suggest that sample preparation is important here. If you use just extraction (aqueous or organic), you will extract a lot of substances, both phenolic and not. Try to use extraction/re-extraction technique with aqueous base to separate acid/phenol fraction, this should help to remove most of non-phenols at least.
Yes you can use NMR. The best option would be to do an extraction and then run solution-state NMR. But you can also try solid-state NMR on the powder if you have access to an instrument.
Rudraksha Dutta Majumdar is correct. You can do solid state NMR directly on the peel. However that is difficult for a number of reasons. Unless you wanted to know something about the compound with the peel matrix, I would extract the organic matter and do liquid state NMR. I also suggest doing chromatography on the extract (HPLC or LC-MS) to isolate the phenol. Lastly, you may want to do supercritical extraction using CO2.
You should extract phenolic compounds from the sample with an appropiate solvent like methanol. After that, purification the phenolic compounds in the extract using sephadex LH20 and silica gel 60-230 mesh until obtain the single spot when detect with UV on TLC plate. Then, identify with NMR.
Dear keerati
Thanks for your response. do you have note/method regarding on your answer?
It's my pleasure. I will send it to you as soon as possible. @Azlan Nazeri
Hm... very interesting. I'd say, unless this is a special case where the peels are very rich in one type of that "phenolic ingredient" it would be only by a strike of luck that one can "identify" the structure. People who do isolation of novel Natural Products would have very little work if things were so simple.
One feature of phenols that can be perhaps useful during initial purification is that they often can be extracted into aqueous NaOH or KOH solutions. Other extractive operations may be necessary, which are normally followed by partitioning on solid phases (Si-gel chromatography, Sephadex, RP HPLC, etc). Analytical HPLC will assist you in assaying the fractions. But even after your component is isolated in a pure form, NMR work (1D-, 2D, nOe-based, etc) alone most probably will not be sufficient (again, unless you are dealing with a relatively simple and well know structure). Typically, HR MS or LCMS data will also be necessary (as Vladimir Khlebnikov indicated to you earlier), and in case of chiral compounds, optical rotation, CD, or chiral chromatography data should also be analyzed.
One perhaps tricky part of your question is that you want to "identify the type" of that compound. I presume that could mean that, for whatever reason, you do not actually need to precisely determine the structure. Perhaps in such case more direct NMR methods may provide some information?
First you should be use a bit of hexane, enough to cover the sample, and use a ultrasonic bath to degrease. Then, you can obtain a methanol extract by the same method (sonication with solvent). After the solvent evaporation, a solution of that dry extract in MeOD can be analysed at the NMR spectrometer. 1H and 13C nmr aromatic signals assigned to phenols ressonances can be observed.
In your case the NMR analyses would not be appropriate to identify the particular phenolic compound inside the pitaya peel unless there is a single compound. I would recommend to extract the peel using appropriate organic solvents (Methanol or Ethyl Acetate), get help from HPLC and HR MS to know the type of compound and purity. Than you can go further NMR analyses for structural determination.
If the question is just to know the types of phenolic compound in your sample, I don't think you need to perform NMR analyses. You can know from the HPLC and LC-MS fragmentation as well.
No! NMR only analyse samples that are about 99% pure. instead use quantification method
really?thanks sakynah for the information. do you have any manual/sop related with nmr, you can share with me. thanks again
do you mean textbook if yes i think PS Kalsi is very good and simple
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