Flavonol Face-Off: Aglycone vs Glycoside
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If quercetin were a person, it’d be the brainy friend who either turns up in a plain white T-shirt (aglycone) or in a full glitter outfit with a tiny sugar backpack (glycoside). Same DNA, totally different entrance — and your gut treats them accordingly.
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Meet the two sides of quercetin
- Aglycone: The “naked” form found in many supplements.
- Glycosides: Quercetin with a sugar stuck on, naturally found in foods like onions and apples (quercetin-3-O-glucoside, isoquercitrin, and rutin).
Think of aglycone as the straight-to-the-point type, and glycosides as the one who uses the VIP lane at airport security. Human studies show onion glycosides can be absorbed over twice as well as aglycone — and rutin trails somewhere in “still waiting for a taxi” territory (Hollman et al., 1997).
Why your gut plays favourites
Glycosides get two possible red-carpet entries:
- LPH enzyme clips the sugar off right on the gut wall, freeing aglycone to slip in.
- SGLT1 transporter ferries the whole sugar-bound package in, then β-glucosidase politely removes the sugar inside.
Either way, your body quickly files quercetin into conjugates (glucuronides, sulphates, methylated forms). That’s not a downgrade — it’s just biochemistry’s way of putting it in a sensible suit before it goes into circulation (Day et al., 2000).
Absorption speed dating: who gets the first kiss?
- Glucosides (like quercetin-3- or 4′-glucoside) hit peak plasma levels in as little as 30–40 minutes.
- Aglycone takes its time, but still gets there — especially with food.
- Rutin? Bring a book. (Olthof et al., 2000)
The “fancy” quercetins
- EMIQ (enzymatically modified isoquercitrin): The biotech makeover — up to 17× higher bioavailability vs aglycone and 40× vs rutin in humans (Owczarek-Januszkiewicz et al., 2022).
- Phytosome®: Wrap quercetin in phospholipids so it dissolves better — human studies show significantly higher blood levels (Riva et al., 2018).
How not to waste your quercetin
- Take it with food — especially some fat: A crossover study found a high-fat meal boosted quercetin’s blood levels by ~45% (Guo et al., 2013).
- Expect conjugates, not free aglycone in your blood test — that’s normal and expected.
- Hierarchy for absorption (human data): EMIQ / Phytosome > food-type glycosides > aglycone > rutin.
Quick Q&A
Do I need to take quercetin on an empty stomach?
Nope — with food is better.
Will I feel it?
It’s more “slow house-cleaning” than “fireworks”. If you notice anything quickly, it’s probably the histamine-calming effect (Weng et al., 2012).
Wrap-up
Whether your quercetin is stripped down or sugar-dressed, the science is clear: form matters. If you’re chasing the fastest, highest uptake, glycosides (especially EMIQ or Phytosome) are your friend. Prefer to keep it simple? Aglycone still works — just bring it to the party with food. Either way, your cells will thank you, your liver will dress it appropriately, and your gut will decide whether it rolls out the red carpet or makes it queue with rutin.
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Disclaimer: This product is not intended to diagnose, treat, cure, or prevent any disease. It is not a medical product. Always consult a healthcare professional before beginning any new dietary supplement.