Respected Sir,
Flavonoid is one of the phenolic components as I know. So, I think that Phenolic content will be definitely higher than flavonoid content.
With Regards,
Tresina
The term phenolics encompass the following. 1) SIMPLE PHENOLS --> A) SINGLE-RING AROMATIC compounds with one or more hydroxyl groups (-OH) such as salicylic acid, catechol, pyrogallol. B) PHENOLIC ACIDS with phenylpropanoid side chains (cinnamoyl esters - caffeic acid, chlorogenic acid, etc., dimers of esters such as curcumin). 2) PROGRESSIVELY COMPLEX PHENOLICS with additional aromatic/heterocyclic ring structures --> lignans/diphenols classified as phytoestrogens; coumarins (containing furans); flavonoids (aglycones) and anthocyanidins; isoflavonoids; isoflavonoid based pterocarpans (phytoalexins); proanthocyanidins (previously known as condensed tannins ); hydrolyzable tannins (gallotannins, derivatives of gallic acid and ellagitannins, derived from gallotannins via oxidative coupling), and so on. Flavonoid glycosides (conjugation with glucose, galactose, rhamnose, etc. -- O and C-glycosides) are generally found at positions (carbons) 3,5,7,8, etc. Other substitutions are acids, prenylation, farnesylation, acylation, methylation, etc.). The glycosides possess free hydroxyl groups at loci other than where sugar moieties conjugate, which can be responsive to Folin-Ciocalteau assay. Swain and Goldstein (1964), in what is now considered as a classic paper, discussed the pros and cons of quantitative analysis of plant phenolics; their final recommendation is the Folin assay, for total phenolics and the vanillin reaction where catechins and proanthocyanidins predominate.
Swain T & Goldstein JL (1964) In “Methods in Polyphenol Chemistry” (Pridham, JB, ed.), pp 131-146. Pergamon Press, Oxford. Harborne, J B. (1989) In: METHODS IN PLANT BIOCHEMISTRY (Series Editors: P M Dey and J B Harborne). VOL 1, Plant Phenolics, Ed. J B Harborne (Academic Press, London) pp. 1-29.
Folin and Denis described a phosphotungstic- phosphomolybdic reagent in 1912, and applied it to the measurement of free and conjugated phenols in the urine; they employed this simple assay to measure L-tyrosine in proteins during their studies on protein hydrolysates at Harvard Medical School. The Folin-Ciocalteau reagent measures all phenols (all phenolic groups found in extracts, including those found in the extractable proteins) in a sample; it is expedient. The assay responds to all reducing substances; there is interference with ascorbate. The method measures the number of potentially oxidizable phenolic groups; the number of phenolic groups per molecule will vary to a great extent, both within and among different phenolic compound subclasses. Gallic acid, stable and readily procurable, furnishes a choice for a standard as the assay measures all phenolics, although this choice may be somewhat arbitrary.
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