Köhler I, Jenett-Siems K, Mockenhaupt F P, Siems K, Jakupovic J, González J C, Hernández M A, Ibarra R A, Berendsohn W G, Bienzle U, Eich E
Planta Med. 2001 Feb;67(1):89-91. doi: 10.1055/s-2001-10630.
The stem bark of Exostema mexicanum (Rubiaceae) is used in Latin American folk medicine as a quinine substitute for malaria treatment. Bioassay-guided fractionation of lipophilic and hydrophilic extracts from the stem bark and branches yielded two previously undescribed 4-phenylcoumarins: 4',8-dihydroxy-5,7-dimethoxy-4-phenylcoumarin (exomexin A) and 3',4'-dihydroxy-5,7,8-trimethoxy-4-phenylcoumarin (exomexin B). Together with five known derivatives the in vitro activities against a chloroquine-sensitive strain (poW) and a chloroquine-resistant strain (Dd2) of Plasmodium falciparum have been evaluated. The most lipophilic compound, 4',5,7,8-tetramethoxy-4-phenylcoumarin (O-methylexostemin) revealed the strongest antiplasmodial activity (IC50 values: 3.6 microg/ml [poW], 1.6 microg/ml [Dd2]).
墨西哥艾克索木（茜草科）的茎皮在拉丁美洲民间医学中被用作治疗疟疾的奎宁替代品。对茎皮和树枝的亲脂性及亲水性提取物进行生物测定导向的分级分离，得到了两种此前未被描述的4-苯基香豆素：4',8-二羟基-5,7-二甲氧基-4-苯基香豆素（艾克索辛A）和3',4'-二羟基-5,7,8-三甲氧基-4-苯基香豆素（艾克索辛B）。连同五种已知衍生物一起，已对它们针对恶性疟原虫氯喹敏感株（poW）和氯喹耐药株（Dd2）的体外活性进行了评估。亲脂性最强的化合物4',5,7,8-四甲氧基-4-苯基香豆素（O-甲基艾克索司亭）显示出最强的抗疟活性（IC50值：对poW为3.6微克/毫升，对Dd2为1.6微克/毫升）。
