BHA, but not O-MeBHA, enhanced the hydrolysis of TCBQ and TrCBQ-OH to DDBQ in a concentration- and pH-dependent manner. (A) BHA enhanced TCBQ hydrolysis in a concentration-dependent manner. (B) BHA enhanced TrCBQ-OH hydrolysis in a concentration-dependent manner. (C) BHA enhanced TCBQ hydrolysis in a pH-dependent manner; TCBQ, 0.05 mM; BHA, 0.20 mM. (D) O-MeBHA could not enhance TCBQ hydrolysis. All incubation mixtures contained the indicated concentration of BHA in phosphate buffer (10 mM, pH 7.0) at room temperature. The reactions were initiated by the addition of TCBQ or TrCBQ-OH (0.05 mM), followed by rapid mixing. DDBQ formation was monitored at 332 nm for 30 min.