 Flavonol

A flavonol is a member of the flavonoid class with a flavone framework bearing a hydroxy group at position3 of its oxygen-containing ring. This combines a position-3 hydroxyl with the position-4 carbonyl group and the characteristic unsaturated ring framework. ChEBI distinguishes this structural class from its unsubstituted parent molecule, 3-Hydroxyflavone.^[ref]

Kaempferol is an example with additional hydroxy groups at positions5,7 and $4^{\prime }$. The prime distinguishes a position on the attached phenyl group from positions in the fused ring system. A class name specifies a structural pattern; it does not assign a single molecular formula, molar mass or biochemical effect to every member.

An original formula check starts with 3-Hydroxyflavone, ${\mathrm{C}}_{15}{\mathrm{H}}_{10}{\mathrm{O}}_3$. Replacing three further carbon-bound hydrogen atoms by three hydroxy groups adds three oxygen atoms without changing the total hydrogen count: each substitution removes one hydrogen and adds one hydrogen as part of OH. The resulting ${\mathrm{C}}_{15}{\mathrm{H}}_{10}{\mathrm{O}}_6$ agrees with the neutral kaempferol record.^[ref]

Using rounded molar masses $238.24$ and $286.24\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$, respectively, $0.250\mathrm{mmol}$ corresponds to $59.56\mathrm{mg}$ of the unsubstituted parent and $71.56\mathrm{mg}$ of kaempferol. Equal amounts of molecules therefore need not mean equal sample masses. The calculation assumes the specified neutral compounds, rather than salts or solvated preparations.

The structural definition is also separate from an antioxidant role. In particular, chemical reduction of an assay reagent by one member is not a universal measure of the class's protective action in living cells. The documented direct MTT reaction of kaempferol illustrates why structure, reaction conditions and biological inference must be kept distinct.^[ref]