Hyperuricemia, excess of uric acid in the blood, is a clinical problem that causes gout and is also considered a risk factor for cardiovascular disease. The enzyme xanthine oxidase (XO) produces uric acid during the purine metabolism; therefore, discovering novel XO inhibitors is an important strategy to develop an effective therapy for hyperuricemia and gout. We found that 3,4-dihydroxy-5-nitrobenzaldehyde (DHNB), a derivative of the natural substance protocatechuic aldehyde, potently inhibited XO activity with an IC₅₀ value of 3 μM. DHNB inhibited XO activity in a time-dependent manner, which was similar to that of allopurinol, a clinical XO inhibitory drug. DHNB displayed potent mixed-type inhibition of the activity of XO, and showed an additive effect with allopurinol at the low concentration. Structure-activity relationship studies of DHNB indicated that the aldehyde moiety, the catechol moiety, and nitration at C-5 were required for XO inhibition. DHNB interacted with the molybdenum center of XO and was slowly converted to its carboxylic acid at a rate of 10⁻¹⁰ mol/L/s. In addition, DHNB directly scavenged free radical DPPH and ROS, including ONOO⁻ and HOCl. DHNB effectively reduced serum uric acid levels in allantoxanamide-induced hyperuricemic mice. Furthermore, mice orally given a large dose (500 mg/kg) of DHNB did not show any side effects, while 42% of allopurinol (500 mg/kg)-treated mice died and their offspring lost their fur. Thus, DHNB could be an outstanding candidate for a novel XO inhibitory drug that has potent activity and low toxicity, as well as antioxidant activity and a distinct chemical structure from allopurinol.

中文翻译：

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3,4-二羟基-5-硝基苯甲醛（DHNB）是一种有效的黄嘌呤氧化酶抑制剂：一种治疗高尿酸血症和痛风的潜在治疗剂

高尿酸血症（血液中尿酸过多）是引起痛风的临床问题，也被认为是心血管疾病的危险因素。黄嘌呤氧化酶（XO）在嘌呤代谢过程中产生尿酸。因此，发现新型XO抑制剂是开发有效的高尿酸血症和痛风疗法的重要策略。我们发现3,4-二羟基-5-硝基苯甲醛（DHNB）是天然物质原儿茶醛的衍生物，有效抑制XO活性，IC 50值为3μM。DHNB以时间依赖性方式抑制XO活性，这与临床XO抑制药物别嘌醇相似。DHNB对XO的活性表现出强力的混合型抑制作用，并在低浓度下与别嘌呤醇表现出加和作用。DHNB的构效关系研究表明，XO抑制需要醛部分，邻苯二酚部分和C-5处的硝化作用。DHNB与XO的钼中心相互作用，并以10 -1 mol / L / s的速率缓慢转化为其羧酸。另外，DHNB直接清除自由基DPPH和ROS，包括ONOO 3和HOCl。DHNB有效地降低了脲基甲酰胺诱导的高尿酸血症小鼠的血清尿酸水平。此外，口服给予大剂量（500 mg / kg）DHNB的小鼠未显示任何副作用，而42％的别嘌醇（500 mg / kg）处理的小鼠死亡，其后代失去了皮毛。因此，DHNB可能是新型XO抑制药物的杰出候选者，该药物具有强大的活性和低毒性，并且具有抗氧化活性和不同于别嘌呤醇的化学结构。