p-Hydroxybenzaldehyde (4-Hydroxybenzaldehyde, 4-Formylphenol, p-Formylphenol), which can be found in the orchids Gastrodia elata, Galeola faberi and vanilla, is a hydroxybenzaldehyde that reacts with NAD+ and H2O to produce 4-hydroxybenzoate, NADH, and 2