Glyceryl laurate and glyceryl undecylenate

Glyceryl laurate and glyceryl undecylenate are esters: each is glycerin joined to a fatty acid. In glyceryl laurate the fatty acid is lauric acid, which has twelve carbons; in glyceryl undecylenate it’s undecylenic acid, which has eleven and one double bond. Both are listed among Quell’s 10 inactive ingredients, and the label makes no specific claim for either.

Where they appear on the label

Quell’s inactive list reads: Caprylyl Glycol, Dead Sea Salt (Sodium Chloride), Emu Oil, Glyceryl Laurate, Glyceryl Undecylenate, Manuka Honey, Polaxamer 188, Sterile Water, Terminalia Chubula and Tromethamine. The two glyceryl ingredients sit next to each other because inactive ingredients on an OTC drug are listed alphabetically under federal labeling rules, 21 CFR 201.66. Laurate comes before undecylenate for that reason alone. No amounts are given for either, which is normal for inactive ingredients.

Glycerin, glycerol and “glyceryl”

Glycerol and glycerin are two names for the same small molecule, a three-carbon chain with three alcohol groups. It’s one of Quell’s actives, listed as Glycerol (1.0%). When a fatty acid is attached to one of glycerol’s alcohol groups, the result is called a monoglyceride, and its ingredient name starts with “glyceryl.” So the word glyceryl tells you the molecule is built on glycerol, while the second word names the fatty acid attached to it.

That shared backbone doesn’t make these esters the same as the active ingredient. On the label, glycerol is an active with its strength shown, and the glyceryl esters are separate inactive ingredients with none.

What is glyceryl laurate?

PubChem, the chemistry database run by the National Institutes of Health, files glyceryl laurate under the name monolaurin. Its record describes the compound as a monoglyceride with a lauroyl group, meaning lauric acid bonded to glycerol, and classes it as a dodecanoate ester. Dodecanoate is the systematic way of saying “from the twelve-carbon acid.”

Lauric acid itself, in PubChem’s description, is a straight-chain, twelve-carbon, medium-chain saturated fatty acid, and it’s the predominant fatty acid in coconut oil and palm kernel oil. Saturated means the carbon chain has no double bonds.

What is glyceryl undecylenate?

PubChem lists it as glyceryl 1-undecylenate, though its record carries no written description. The fatty acid half, undecylenic acid, has a fuller entry: PubChem identifies it as 10-undecenoic acid, an eleven-carbon acid with its double bond at the tenth position, near the end of the chain, and notes that it’s derived from castor oil. Joined to glycerol, it becomes glyceryl undecylenate.

Comparing the two side by side

• Both: a monoglyceride, meaning one fatty acid attached to glycerol.
• Glyceryl laurate: built from lauric acid, twelve carbons, no double bonds.
• Glyceryl undecylenate: built from undecylenic acid, eleven carbons, one double bond near the end.
• Sources PubChem names for each acid: coconut and palm kernel oils for lauric acid; castor oil for undecylenic acid.
• On Quell’s label: both inactive, both unquantified, neither tied to a stated use.

What they do in Quell

The label doesn’t say, and we won’t guess. Inactive ingredients are named on a Drug Facts panel but not explained. The product’s uses are tied to its actives, Glycerol (1.0%), Polysorbate 80 (1.0%) and Light Mineral Oil (0.5%), and the Uses line reads: For use as a protectant against further irritation or to relieve dryness of the eye. Separately, Quell is designed to reinforce the tear film’s oil layer to help reduce moisture loss, but that statement is about the formula as a whole, not about any one ingredient on the inactive list.

Do these ingredients affect how Quell looks?

The label describes the product this way: Product appears as a milky brown solution. It doesn’t attribute the color or texture to any particular ingredient. What matters for you is the label’s Do not use line, “If this product changes color,” so it’s worth knowing what your bottle looks like when it’s fresh. Why is Quell milky brown? covers the look.

Coconut, castor and sensitivities

Knowing the source oils can help people who track what they react to. If you’ve had problems with coconut- or castor-derived ingredients in other products, or with anything on Quell’s list, show the label to a pharmacist before trying it. The label’s own caution is about a different ingredient: Caution should be used in those with egg or bird allergies — For use in the eyes only. And if any drop leaves your eyes painful or your vision changed, stop and see a doctor.

For the rest of the inactive list, see the natural ingredients in Quell, and for the actives, glycerol in eye drops. The full label is on our Drug Facts page.