Preparation of Vanilloid Compound Solutions

The following were prepared as 50 mM stock solutions in 70% (v/v) EtOH and adjusted to pH 7 using 2.5 M NaOH when required: 2-vanillic acid (2-hydroxy-3-methoxybenzoic acid, ABCR, Karlsruhe, Germany, Cat. No. AB177480), 2-vanillin (2-hydroxy-3-methoxybenzaldehyde, ABCR, Cat. No. AB117268), acetovanillone (4′-hydroxy-3′-methoxyacetophenone, ABCR, Cat. No. AB125832), benzaldehyde (Acros, Geel, Belgium, Cat. No. 378361000), benzoic acid (ABCR, Cat. No. AB113879), benzyl acetate (ABCR, Cat. No. AB131641), benzyl alcohol (ABCR, Cat. No. AB171491), ethyl-vanillate (ABCR, Cat. No. AB178082), ethyl-vanillin (3-ethoxy-4-hydroxybenzaldehyde, ABCR, Cat. No. AB126381), eugenol (ABCR, Cat. No. AB111881), homovanillic acid (Sigma, St Louis, MO, USA, Cat. No. H1252-1G), isovanillic acid (3-hydroxy-4-methoxybenzoic acid, ABCR, Cat. No. AB117271), isovanillin (3-hydroxy-4-methoxybenzaldehyde, ABCR, Cat. No. AB117270), methyl-vanillate (ABCR, Cat. No. AB132603), protocatechualdehyde (3,4-dihydroxybenzaldehyde, ABCR, Cat. No. AB110948) and vanillin (ABCR, Cat. No. AB117415). Vanillic acid (Fluka, Buchs, Switzerland, Cat. No. 94770-10G) was prepared as a 50 mM stock solution in water and adjusted to pH 7 with 2.5 M NaOH. All solutions were used at a final concentration of 250 µM unless otherwise indicated. Tetracycline (Sigma, Cat. No. T7660) was prepared as a 1 mg/ml stock solution in H₂O, and erythromycin (Fluka, Cat. No. 45673) as a stock solution of 1 mg/ml in ethanol. Both antibiotics were used at a final concentration of 2 µg/ml.