We determined the phenolics in studied plant by folin-ciocalteau method. We used 1 mg/mL of crude ethanolic extracts for detection. It can not change the color of the Folin reagent. It mean that phenolics is not found in the studied plant, or not? Is there possible?
Phenolics are present every plant and tissue. Basically it provide help in plant protection from diseases ans cell wall strengthening. Crud extract possess small amount of phenolics and tissue type also influence the content of total phenolics especially in inner storage tissue of plant. Extraction procedure such as extraction time, particle size, solvent used and storage are other important factors. Low phenolic bearing plant/tissue can easily become undetectable due above mentioned factors. for increase your plant material concentration and reduce the impact of these factors.
Do your controls change the color of Folin? Maybe there is a problem with your reagent or method? You could try use an extract of green or black tea from your nearby supermarket as a quick test.
I second Shane's comment. Check the reagent quality with control(s) to make sure your test system is working appropriately. See attached article for one of the protocols which I have used previously.
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what plant extracts are you investigating? How were they extracted?
Try used more concentration of extract and use a control as quercetin for discarding any problem with the reagents.
Concentrate the extract and repeat the process. the extract should be fresh, check with the lab wares.
You can test the reagent with a standard compound (like a flavonoid or phenolic acid). If the reagent is ok test the extract at higher concentration. Don't expect to find high polyphenolic content in apolar extracts (essential oils, hexane, etc), but that doesn't seem to be your case. Also some plants have a much higher content of other compounds - like caffeine in tea plant. HPLC may give you an idea of what is in there.
It is possible to be in low quantity or the Folin reagent to be degradated
Plants extracts will either be phenol or flavonoid rich.. So test both of them to come to conclusion. Though its impossible for a plant to have zero phenolic content. Check my methods and result.
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Tea Polyphenols are extracted best in 70% Methanol in finely ground leaf at 70oC. Check out my publication.
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Plant extract are rich in phenolic compounds. Repeat the experiment.
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