Flavanones: The Citrus Side of the Flavonoids

Three names, one subclass

Three names describe this same group of plant compounds in the 2016 overview by Panche and colleagues [1]. That is the first hurdle for anyone reading around the subject. You meet one term on a chemistry page, a second in a food science table, a third in a review paper, and all three point at an identical structure.

Flavonoids are a large family of compounds made by plants. Inside that family sit several subclasses, sorted by small differences in one part of the molecule. Flavanones are one of those subclasses, and they are the ones most often discussed in connection with citrus fruit.

The skeleton is shared across the family: three rings, labelled A, B and C [1]. Ring C is where the sorting happens. Chemists number the carbons in that ring, and two of those numbers do most of the work in every classification table you will come across: carbon 2 and carbon 3 [1].

One of the three group names carries the prefix dihydro. It is not decoration. It records two hydrogen atoms sitting at positions where the neighbouring subclasses hold something else [1]. Chemical names are often small instructions, once you know where to look.

Read the table from the top down and the logic falls into place. Family, then ring, then position, then bond, then the consequence of that bond. Nothing in the list is a matter of opinion. It is the kind of information that stays put while the rest of the research around plant compounds keeps moving.

One bond, two different answers

Flavones and flavonols carry a double bond between carbon 2 and carbon 3 of ring C [1]. Flavanones do not. That is the whole distinction. Two structures can look near enough identical when sketched quickly, and still belong on separate shelves of the classification because of what happens across that one stretch.

A double bond holds the neighbouring atoms in a rigid, flat arrangement. Take it away and carbon 2 gets a fourth partner and a bit of freedom. That is what the dihydro prefix is recording: two extra hydrogens, one position, a different subclass name [1].

It also explains why the two groups behave differently on paper. Flavones and flavonols have nothing to sort out at carbon 2, because the double bond leaves no room for two arrangements. Flavanones do. One position, two answers, and a second layer of naming that follows from it.

Anyone comparing two literature tables will find this useful. If a source groups flavanones with flavones without comment, it is grouping by broad family rather than by structure, and the C2 to C3 detail has been left out. That is not wrong, it is just a coarser sort. The finer sort is the one Panche and colleagues set out in 2016 [1], and it is the one worth carrying into anything you read next.

Restraint helps here too. The structure is documented. What each structure does inside the body is a separate question with a separate, much thinner evidence base, and the two should not be run together.

The carbon at position 2 comes in two versions

Two arrangements, one set of parts

Hold up both hands. Same components, same order, and still you cannot lay one on top of the other and have everything line up. That is mirror-image chemistry in one gesture.

Carbon 2 of a flavanone is a stereocentre. Four different neighbours sit around it, and there are exactly two ways to arrange them. The two versions share a molecular formula, a molecular weight, and a name in most casual writing. They are not the same molecule. Chemists label them with a letter, which is where the S in 2S comes from.

None of this arises in flavones or flavonols, because the double bond at that position removes the choice [1]. So the mirror-image question is specific to this subclass. It is a direct consequence of the bond that is missing.

Fruit from the tree keeps to 2S

In citrus material as it grows, the flavanones are close to all 2S. One arrangement, near enough exclusively. Why the plant settles on that one rather than the other is enzyme chemistry inside the fruit, and it is not something this page will settle.

The practical point is about reading data. A figure reported under a single flavanone name does not, on its own, tell you which of the two forms was measured, or whether the method separated them at all. Some analytical methods do. Many do not, because they were never designed to.

So two numbers from two papers can describe two slightly different things. Worth knowing before you compare them. It is the same habit that serves you well anywhere in plant chemistry: check what the method actually measured before you take the number at face value.

Flavonoids show up in hemp as well

Flavanones are the citrus story. Flavonoids as a whole are not a citrus exclusive. Hemp extract contains flavonoids alongside its cannabinoids and terpenes, all from the same plant material [2].

Whole-plant composition, said plainly

A whole-plant extract keeps that mixed composition rather than isolating one compound from it [2]. The entourage effect is the working hypothesis that the compounds in such a mixture may act together rather than each on its own, and the research behind it is at an early stage with no firm conclusions available [2]. That is the honest state of it. Interesting, documented as a chemical mixture, unresolved as a biological question.

We have been working with cannabinoids since 2014, and the position has not needed to change much in that time. Composition is measurable. Interaction between components is not, at least not yet, and saying so is part of the job.

What sits in a batch report

A cannabinoid analysis reports cannabinoids. That is what the method is built for, and it is why our batch reports list CBD, CBG, CBC, CBN and CBDa rather than a flavonoid column. Full-spectrum oils are non-intoxicating and stay within legal THC limits, and the report is where you verify that rather than take our word for it.

If flavonoid content matters to you, that is a different analysis with a different method, and no cannabinoid report answers it. Worth knowing which document answers which question.

Since 2014, one standard: know what is inside. For flavanones, what is inside is a three-ring skeleton, one saturated position in ring C [1], and a carbon that comes in two versions of which citrus uses one.