The critical function of dihydroorotate dehydrogenase (DHODH) in pyrimidine synthesis attracted a great interest throughout beyond decades. Inhibitors of human DHODH (hDHODH) have validated efficacy for remedy of many immunological diseases. Brequinar and leflunomide are examples of such compounds. However, most of such immunosuppressive medications suffer from a lot of side effects and accompanied by adverse metabolic disturbances and toxicities. So that, immunomodulation utilizing natural products received the attention of many researchers. In this study, computer-aided molecular docking, molecular dynamic (MD) simulations and biochemical testing were utilized to find new pharmacologically active chemical entities from natural sources to combat immunosuppressive diseases. More specifically, Glide docking was used for a structure-based virtual screening of in-house 3D database of compounds retrieved from some traditionally known immunomodulatory plants surveyed from literature. The top five scored plants were found to be Zingiber officinale, Curcuma longa, Glycyrrhiza glabra, Allium sativum and Olea europaea. In vitro hDHODH inhibitory assays illustrated the ability of Allium sativum and silymarin standard hits; specifically, silibinin, to significantly inhibit the hDHODH enzyme. Molecular docking and MD simulations revealed a strong binding of the discovered hits within the active site. Following that, the most promising hits were tested separately with brequinar in a fixed-ratio combination setting to assess their combined effects on hDHODH catalytic inhibition. The binary combination of silibinin and brequinar revealed that in this combination, brequinar could be utilized at a dose 9.33-fold less when compared to its single-use to produce 99% inhibition for hDHODH enzyme. These findings confirmed that this binary mixture is an excellent combination providing better therapeutic effects and lower side effects.

在随后的几十年中，二氢乳清酸脱氢酶 (DHODH) 在嘧啶合成中的关键功能引起了人们的极大兴趣。人 DHODH 抑制剂 (hDHODH) 已验证了治疗许多免疫疾病的功效。Brequinar 和来氟米特是此类化合物的例子。然而，大多数此类免疫抑制药物都有很多副作用，并伴有不良的代谢紊乱和毒性。因此，利用天然产物进行免疫调节受到了众多研究者的关注。在这项研究中，利用计算机辅助分子对接、分子动力学 (MD) 模拟和生化测试从天然来源中寻找新的具有药理活性的化学实体来对抗免疫抑制疾病。进一步来说，Glide 对接用于基于结构的虚拟筛选内部 3D 化合物数据库，这些化合物是从文献中调查的一些传统上已知的免疫调节植物中检索到的。发现得分前五名的植物是生姜、姜黄、光果甘草、大蒜和油橄榄。体外 hDHODH 抑制测定说明了大蒜和水飞蓟素标准命中的能力；具体而言，水飞蓟宾可显着抑制 hDHODH 酶。分子对接和 MD 模拟揭示了在活性位点内发现的命中的强烈结合。之后，最有希望的命中在固定比例组合设置中分别与 brequinar 进行测试，以评估它们对 hDHODH 催化抑制的综合影响。水飞蓟宾和 brequinar 的二元组合表明，在这种组合中，brequinar 的使用剂量比其单次使用低 9.33 倍，对 hDHODH 酶产生 99% 的抑制。这些发现证实，这种二元混合物是一种极好的组合，可提供更好的治疗效果和更低的副作用。