The natural products pulchrol and pulchral, isolated from the roots of the Mexican plant Bourreria pulchra, have previously been shown to possess antiparasitic activity towards Trypanosoma cruzi, Leishmania braziliensis and L. amazonensis, which are protozoa responsible for Chagas disease and leishmaniasis. These infections have been classified as neglected diseases, and still require the development of safer and more efficient alternatives to their current treatments. Recent SARs studies, based on the pulchrol scaffold, showed which effects exchanges of its substituents have on the antileishmanial and antitrypanosomal activity. Many of the analogues prepared were shown to be more potent than pulchrol and the current drugs used to treat leishmaniasis and Chagas disease (miltefosine and benznidazole, respectively), in vitro. Moreover, indications of some of the possible interactions that may take place in the binding sites were also identified. In this study, 12 analogues with modifications at two or three different positions in two of the three rings were prepared by synthetic and semi-synthetic procedures. The molecules were assayed in vitro towards T. cruzi epimastigotes, L. braziliensis promastigotes, and L. amazonensis promastigotes. Some compounds had higher antiparasitic activity than the parental compound pulchrol, and in some cases even benznidazole and miltefosine. The best combinations in this subset are with carbonyl functionalities in the A-ring and isopropyl groups in the C-ring, as well as with alkyl substituents in both the A- and C-rings combined with a hydroxyl group in position 1 (C-ring). The latter corresponds to cannabinol, which indeed was shown to be potent towards all the parasites.
墨西哥植物 Bourreria pulchra 的根部中分离出的
天然产物 pulchrol 和 pulchral 已被证明具有抗原虫活性,对克氏锥虫、巴西利亚利什曼虫和亚马逊利什曼虫等原虫引起的光谷病和利什曼病具有活性。这些感染已被归类为被忽视的疾病,仍需要开发更安全、更有效的替代治疗方法。最近的结构活性关系研究,基于 pulchrol 结构骨架,展示了其取代基之间交换对抗利什曼虫和抗克氏锥虫活性的影响。许多制备的类似物显示比 pulchrol 和目前用于治疗利什曼病和光谷病的药物(分别为米尔特霉素和苯硝唑)更具有潜力。此外,还发现了可能发生在结合位点中的一些相互作用迹象。在这项研究中,通过合成和半合成方法制备了在两个或三个不同位置的两个
三环中进行修饰的12个类似物。这些分子在体外对克氏锥虫的梭形体、巴西利亚利什曼虫的梭形体和亚马逊利什曼虫的梭形体进行了测定。一些化合物的抗原虫活性比母体化合物 pulchrol 更高,甚至有时比苯硝唑和米尔特霉素还要高。在这个子集中效果最好的组合是 A 环中的酮功能基和 C 环中的异丙基,以及 A 和 C 两环中的烷基取代基与位置 1(C 环)的羟基结合。后者对所有寄生虫都显示出了强大的活性,这对应于
大麻酚。