Vanillic acid (4-hydroxy-3-methoxybenzoic acid) is an aromatic phenolic acid that arises as the oxidized form of vanillin. It is a white to slightly yellowish crystalline powder with a gentle, vanilla-like scent; it is stable under ambient conditions, poorly soluble in water, and readily soluble in organic solvents. Owing to its favorable sensory and antioxidant properties, it is used as a flavor and fragrance ingredient in foods and cosmetics and as an intermediate in synthesis.
The aim of this thesis was to prepare and perform an olfactory evaluation of volatile lipophilic derivatives of vanillic acid for potential use in cosmetics. We carried out 11 chemical reactions, using vanillic acid and its esters methyl 4-hydroxy-3-methoxybenzoate and ethyl 4-hydroxy-3-methoxybenzoate as starting materials. Reaction progress was monitored by TLC; products were isolated by extraction and separated/purified by column adsorption chromatography. The resulting compounds were structurally identified and confirmed by ¹H NMR (400 MHz; CDCl₃/DMSO-d₆), with data processed in MestReNova.
Olfactory assessment was performed on ethanolic solutions of selected products and two blank controls (water, ethanol). Eighteen volunteers (20–52 years) carried out a blinded evaluation of odor pleasantness (pleasant/unpleasant), odor intensity (1 = no odor, 4 = very strong), and provided associations for each sample. All analyzed samples were rated predominantly pleasant. The most pleasant was 3-methoxy-4-(propanoyloxy)benzoic acid (mainly floral–fruity notes), while the strongest odor was recorded for ethyl 4-hydroxy-3-methoxybenzoate; the vanillic acid standard followed closely in intensity, and methyl 4-acetoxy-3-methoxybenzoate was of medium strength.
Overall, the results support the hypothesis that synthetic volatile lipophilic derivatives of vanillic acid possess pleasant odors and represent promising fragrance candidates for incorporation into cosmetic products.
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