Flavonols: the pigment group hiding in onion skin

15 carbons, then one position

Bound, uneven, sample by sample

Pull a plant apart and the flavonols rarely show up as tidy single molecules. In living tissue these compounds are usually not free at all [1]. They sit bound to something larger. So a fresh leaf, a dried leaf and a finished extract are three different starting points, even when the species printed on the label is identical.

Then comes the uneven part. Panche's 2016 overview notes that the same plant can differ from one side to the other [1]. One side of the shrub, one side of the row, one side of the bulb. Same soil, same morning, different figures. That observation quietly does more work than any average printed in a food composition table, because an average hides the very variation the plant produced.

Which leaves a modest, useful rule. A flavonol figure describes a sample, not a species. Which part, harvested when, prepared how, measured by which method. Since 2014 we have worked the same way with hemp: the batch is the unit you can check, not the plant name on the front of the bottle.

• The part of the plant you sample matters, since these compounds are not spread evenly through living tissue [1].
• Because they are usually bound rather than free [1], preparation sits between the plant and the number on paper.
• Two samples from one individual plant can disagree, which is what the 2016 overview by Panche describes [1].
• A species name is not a measurement. A batch reference with a date and a stated method is.
• Colour alone is a weak guide, because the neighbouring flavanols are not yellow pigments at all.
• Flavonoid is a heading covering several subclasses, so the word by itself does not say which compounds were found [1].

One letter apart, two branches

Flavonol and flavanol. One letter of difference in writing, one ketone and one double bond in chemistry. Flavanols, written properly as flavan-3-ols, keep the hydroxyl at position 3 but have lost the ketone at position 4 and the double bond in that ring. Flavonols hold all three features at once [1]. That is the entire boundary between them.

The names most people already know sit on the flavanol side: the catechins of tea and cocoa. They are not the yellow pigments, and they do not behave the same way in the plant. A page about tea polyphenols and a page about pigments in outer plant tissue are describing two branches, not one branch with two spellings.

Both branches appear under the flavonoid heading in Panche's 2016 overview [1], and that shared heading is where the mix-up begins. Same family, separate subclass, terms that are not interchangeable [1]. A search box will not fix the letter for you, and neither will a pack of capsules. When a text swaps between the two spellings inside a single paragraph, read that as a sign the author is not tracking the chemistry.

• Flavonol: hydroxyl at position 3, ketone at position 4, double bond in the same ring [1].
• Flavone: the same frame, with the 3-hydroxyl removed.
• Flavan-3-ol: the hydroxyl stays, while the ketone and the double bond go.
• Catechins from tea and cocoa belong on the flavanol side of that split.
• Both groups share the flavonoid heading in the 2016 overview, which is why a single letter carries real weight [1].

Where hemp actually fits

Hemp produces flavonoids, as any flowering plant does [1]. Ordinary botany, and worth stating plainly, because hemp content often gets read as a special case when it is not. The plant sits in the same family table as tea, cocoa and every onion in the shop.

The compounds carrying hemp's own name here are the cannflavins, recorded in the 2005 chemical inventory of the plant by ElSohly and Slade [2]. They are flavones, not flavonols [2]. Structurally that places them on the neighbouring branch, one hydroxyl group away from the flavonol pattern [2]. Close enough to be muddled in a headline. Far enough that the two labels cannot be swapped.

So a bottle of hemp extract is not a flavonol product, and it should not be read as one. Hemp's line in this family runs through the flavones [2]. If flavonols specifically are what you are after, you are looking at the plants where the 3-hydroxyl version is the one being described [1].

What the batch paperwork covers

Our own documentation is narrower than a plant-chemistry map, and deliberately so. Each batch is analysed independently for cannabinoid content, so the figure on the label can be compared against the report behind it. Plant pigment groups are not part of that analysis, and we would rather say that than imply a longer list. Products are non-intoxicating and within legal THC limits. Since 2014, one standard: know what is inside, and be able to show it.