Toluquinol

Analytical standards of 2,5-dihydroxybenzaldehyde (compound 2; 98% purity), m-cresol (3; 99% purity), 3-hydroxybenzyl alcohol (4; 99% purity), toluquinol (5; ≥98% purity), 3-hydroxybenzaldehyde (6; ≥99% purity), 3-hydroxybenzoic acid (7; 99% purity), 2,5-dihydroxybenzoic acid (8; 98% purity), 2,4-dihydroxybenzaldehyde (10; 98% purity), 3,4-dihydroxybenzaldehyde (11; 97% purity), 3,5-dihydroxybenzaldehyde (12; 98% purity), 2-hydroxybenzaldehyde (13; 98% purity), and 4-hydroxybenzaldehyde (14; 98% purity) were procured from Sigma-Aldrich, Seoul, Korea. Methanol, acetone, and water used for the following experiments were of high-performance liquid chromatography (HPLC) grade.

Two types of formulations, namely, a wettable powder (T-WP) and a soluble concentrate (T-SL), were prepared using toluquinol (also known as methylhydroquinone; Sigma-Aldrich). To prepare T-WP, 20 g of toluquinol suspended in a minimal volume of acetone was combined with 15 g of synthetic hydrated silicon dioxide (white carbon; Rhodia Asia Pacific Pte. Ltd., Singapore). After evaporating the acetone in a fume hood, 5 g of CR-100 (a wetting agent; Yoosung Chemical R&T Co. Ltd.), 5 g of CR-SDS (a surfactant; Yoosung Chemical R&T Co. Ltd.), and 55 g of kaolin (a dispersant) were added. Finally, the mixture was ground using an electric powder grinder. To prepare T-SL, 10 g of toluquinol suspended in 40 ml of ethanol was mixed with 20 g of CR-MC33 (an emulsifier; Yoosung Chemical R&T Co. Ltd.) and water to obtain 100 ml of the final product.