Ono K, Nakane H, Fukushima M, Chermann J C, Barré-Sinoussi F
Laboratory of Viral Oncology, Aichi Cancer Center Research Institute, Nagoya, Japan.
Eur J Biochem. 1990 Jul 5;190(3):469-76. doi: 10.1111/j.1432-1033.1990.tb15597.x.
Four flavonoids, 5,6,7-trihydroxyflavone (baicalein), 3,3',4',5,7-pentahydroxyflavone (quercetin), 3,3',4',5,6,7-hexahydroxyflavone (quercetagetin) and 3,3',4',5,5',7-hexahydroxyflavone (myricetin), were found to be potent inhibitors of reverse transcriptases from Rauscher murine leukemia virus (RLV) and human immunodeficiency virus (HIV). Under the reaction conditions employed, any one of these flavonoids almost completely inhibited the activity of RLV reverse transcriptase at a concentration of 1 microgram/ml. HIV reverse transcriptase was inhibited by 100%, 100%, 90% and 70% in the presence of 2 micrograms/ml quercetin, myricetin, quercetagetin and baicalein, respectively. The mode of inhibition of these flavonoids was competitive (RLV reverse transcriptase) or partially competitive (HIV reverse transcriptase) with respect to the template.primer complex, (rA)n.(dT), and noncompetitive with respect to the triphosphate substrate, dTTP. The Ki values for RLV reverse transcriptase were found to be 0.37 microM and 0.08 microM for baicalein and quercetin, respectively and those for HIV reverse transcriptase were 2.52 microM, 0.52 microM, 0.46 microM and 0.08 microM for baicalein, quercetin, quercetagetin and myricetin, respectively. Comparative studies with other flavonoids (hydroxyflavones, dihydroxyflavones and polyhydroxyflavones and flavanones) carried out to clarify the structure/activity relationships, revealed that the presence of both the unsaturated double bond between positions 2 and 3 of the flavonoid pyrone ring, and the three hydroxyl groups introduced on positions 5, 6 and 7, (i.e. baicalein) were a prerequisite for the inhibition of reverse transcriptase activity. Removal of the 6-hydroxyl group of baicalein required the introduction of three additional hydroxyl groups at positions 3, 3' and 4' (quercetin), to afford a compound still capable of inhibiting the reverse transcriptase activity. Quercetagetin which contains the structures of both baicalein and quercetin, and myricetin which has the structure of quercetin with an additional hydroxyl group on the 5' position also proved strong inhibitors of reverse transcriptase activity. The inhibition by baicalein of reverse transcriptase is highly specific, whereas quercetin and quercetagetin were also strong inhibitors of DNA polymerase beta and DNA polymerase I, respectively. Myricetin was also a potent inhibitor of both DNA polymerase alpha and DNA polymerase I.
已发现四种黄酮类化合物，即5,6,7 - 三羟基黄酮（黄芩素）、3,3',4',5,7 - 五羟基黄酮（槲皮素）、3,3',4',5,6,7 - 六羟基黄酮（栎精）和3,3',4',5,5',7 - 六羟基黄酮（杨梅素），是劳氏鼠白血病病毒（RLV）和人类免疫缺陷病毒（HIV）逆转录酶的有效抑制剂。在所采用的反应条件下，这些黄酮类化合物中的任何一种在浓度为1微克/毫升时几乎能完全抑制RLV逆转录酶的活性。在存在2微克/毫升槲皮素、杨梅素、栎精和黄芩素的情况下，HIV逆转录酶分别被抑制100%、100%、90%和70%。这些黄酮类化合物的抑制模式相对于模板 - 引物复合物（rA）n·（dT）是竞争性的（RLV逆转录酶）或部分竞争性的（HIV逆转录酶），而相对于三磷酸底物dTTP是非竞争性的。已发现黄芩素和槲皮素对RLV逆转录酶的Ki值分别为0.37微摩尔和0.08微摩尔，而黄芩素、槲皮素、栎精和杨梅素对HIV逆转录酶的Ki值分别为2.52微摩尔、0.52微摩尔、0.46微摩尔和0.08微摩尔。为阐明结构 - 活性关系而进行的与其他黄酮类化合物（羟基黄酮、二羟基黄酮、多羟基黄酮和黄烷酮）的比较研究表明，黄酮吡喃环2和3位之间存在不饱和双键以及在5、6和7位引入三个羟基（即黄芩素）是抑制逆转录酶活性的前提条件。去除黄芩素的6 - 羟基需要在3、3'和4'位引入另外三个羟基（槲皮素），以得到一种仍能抑制逆转录酶活性的化合物。含有黄芩素和槲皮素结构的栎精以及在5'位有一个额外羟基的具有槲皮素结构的杨梅素也被证明是逆转录酶活性的强抑制剂。黄芩素对逆转录酶的抑制具有高度特异性，而槲皮素和栎精分别也是DNA聚合酶β和DNA聚合酶I的强抑制剂。杨梅素也是DNA聚合酶α和DNA聚合酶I的有效抑制剂。
