= Flavonol
A \b[<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>.<Flavonols in ChEBI>[CHEBI:28802, definition and class-member relations; CHEBI:5078, parent-molecule definition]{ref}
<Kaempferol> is an example with additional <hydroxy groups> at positions5,7 and $4'$. 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>, $\mathrm{C_{15}H_{10}O_3}$. 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 $\mathrm{C_{15}H_{10}O_6}$ agrees with the neutral <kaempferol> record.<Kaempferol in ChEBI>[CHEBI:28499, substitution pattern and molecular formula]{ref}
Using rounded <molar masses> $238.24$ and $286.24\,\mathrm{g\,mol^{-1}}$, 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.<Interference of plant extracts, phytoestrogens and antioxidants with the MTT tetrazolium assay by Regina Bruggisser and others>[Abstract, cell-free reduction]{ref}
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