More differentials: OR2A25, OR11A1, OR51L1.

After finding that OR51E1 agonists have a cheesy note, the author has targeted three more receptors with agonist/antagonist differential experiments.

For OR2A25, the aroma of unmixed geranyl acetate was compared with that of the same compound mixed with methyl salicylate. Geranyl acetate is an agonist for OR2A25. Methyl salicylate is an antagonist for this receptor, as well as for OR5P3, OR1A1, and OR8D1. Geranyl acetate is also an antagonist for OR5P3 and OR1A1, and is neutral to OR8D1. Therefore, this differential pair singles out OR2A25 for observation. The aroma note present in the unmixed agonist and absent or reduced in the mixture was a tobacco-like, dark leafy, papery quality.

Geosmin and 2-ethylfenchol are agonists of OR11A1. Allyl phenylacetate is an antagonist of OR11A1, OR5P3, and OR10G3. 2-ethylfenchol is neutral to OR10G3 and an antagonist of OR5P3; geosmin would not be expected to be an OR10G3 agonist. Allyl phenylacetate was unavailable so allyl phenoxyacetate, which has a similar aroma, was used. Both mixtures smelled rooty, humus, and musty, but the non-antagonized mixture also had a watery-mineral or wet rock note to its odor.

Allyl phenylacetate is an agonist of OR2W1, OR51L1, and OR1A1. Bourgeonal is an antagonist of OR51L1 and OR2W1, among other receptors. Of bourgeonal’s other antagonist receptors, only OR3A1 and OR51I2 are unknown for allyl phenylacetate; the others are neutral to that compound. Therefore, the differential is a test of OR51L1+OR2W1. Allyl phenoxyacetate was once again substituted in place of allyl phenylacetate. The note present in the pure compound and reduced in the antagonized mixture was a pruny, honey, buttery quality.

Therefore the perceptual quality contributed by OR2A25 is a tobacco-like darkness, while that contributed by OR11A1 is probably a watery mineral note, and that of OR51L1 may be a honey-buttery or pruny-honey note.

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