中国乌头属植物药用亲缘学研究

A pharmacophylogenetic study of Aconitum L. (Ranunculaceae) from China

毛茛科Ranunculaceae乌头属AconitumL.植物作为有毒植物及药用植物一直受到广泛的关注。本属全世界约有300余种,其中超过半数分布在中国。本文在总结乌头属二萜生物碱的化学分类及其分布、特征性二萜生物碱及其分类价值以及二萜生物碱的生源关系及其分类学意义的基础上,结合其毒性和疗效讨论了国产乌头属植物亲缘关系、化学成分和疗效及毒性之间的相关性,亦即药用亲缘学的初步研究。发现牛扁亚属subgen.Lycoctonum是以牛扁碱和C18-二萜生物碱为主的类群,由于其毒性中等,因而是寻找镇痛、抗炎等新药的一个对象。从二萜生物碱化学成分来看,露蕊乌头亚属subgen.Gymnaconitum并不显得最为进化,对其分类位置尚难作出最后的结论。乌头亚属subgen.Aconitum亚属下系之间的化学分类表现出如下特征:(1)唐古特乌头系ser.Tangutica和圆叶乌头系ser.Rotundifolia是以内酯型二萜生物碱为主的类群,毒性较小,是新药寻找的重点研究类群。保山乌头系ser.Bullatifolia以C20-二萜生物碱如光翠雀碱和宋果灵以及C19-二萜生物碱如乌头碱、滇乌碱和尼奥灵等为主。短柄乌头系ser.Brachypoda显示以3-乙酰乌头碱、乌头碱、伏乌碱等高度进化的乌头碱型二萜生物碱为主,胺醇类如尼奥灵次之,有时共存其他纳哌啉型C20-二萜生物碱的特征。准噶尔乌头系ser.Grandituberosa的化学特征是以高度进化的乌头碱型如乌头碱等和比较原始的胺醇如塔拉萨敏、尼奥灵等以及C20-二萜生物碱为主,均有较大毒性。褐紫乌头系ser.Brunnea则以C20-二萜生物碱如光翠雀碱和宋果灵为主,杂有高度进化的乌头碱型二萜生物碱如乌头碱等成分。化学分类上不支持其独立成为一个分支。以上各系组成乌头亚属的原始和中间过渡类群。其中唐古特乌头系和圆叶乌头系最为相近,褐紫乌头系可能是连接保山乌头系和短柄乌头系的“桥梁”,而准噶尔乌头系更靠近保山乌头系。(2)显柱乌头系ser.Stylosa是以含大茴香酸酯基的乌头碱型二萜生物碱以及塔拉萨敏和查斯曼宁胺醇类为主的类群,是块根较大的“大乌头”的主要来源,具有很大的毒性。兴安乌头系ser.Ambigua以含大茴香酸酯基的乌头碱型和原始胺醇类如塔拉萨敏、尼奥灵等二萜生物碱为主。蔓乌头系ser.Volubilia是以含大茴香酸酯基/苯甲酸酯基的乌头碱型和塔拉萨敏胺醇类以及高度进化的乌头碱型二萜生物碱为主的中间过渡类群。乌头系ser.Inflata以含15-羟基的单酯、双酯或多酯以及胺醇类乌头碱型二萜生物碱为主,且酯基中无大茴香酸酯基,此系是草乌的主要植物来源,具有很大的毒性,应十分慎用。这些系可能代表乌头亚属进化的类群。其中显柱乌头系与兴安乌头系可能较近缘。蔓乌头系可能是连接显柱乌头系/兴安乌头系与乌头系的中间类群。另外,保山乌头系、短柄乌头系和准噶尔乌头系可能是直接向显柱乌头系、蔓乌头系和乌头系过渡的较为原始的类群。(3)岩乌头系ser.Racemulosa从化学分类角度来看是一个特殊的类群,支持其独立成一个分支。其化学特征以牛扁碱型和乌头碱型的胺醇二萜生物碱如牛扁碱、异塔拉萨亭定和C20-二萜生物碱为主。如果单纯从化学成分来看,它与牛扁亚属植物似乎有一定关系。

Aconitum L. （Ranunculaceae） is a large genus of about 300 species distributed in the temperate regions of the Northern Hemisphere. This genus consist of three well-circumscribed subgenera, subgen. Lycoctonum （DC.） Peterm., subgen. Aconitum and subgen. Gymnaconitum （Stapf） Rapaics. The southwestern China, particularly its Hengduan Mountains region, is the most important center of diversity and speciation of the genus. Many species in this genus have been used as poisonous and medicinal plants. This paper is to evaluate the taxonomic value of diterpenoid alkaloids mainly at subgeneric and serial levels of the genus Aconitum based on an analysis of the distribution of diterpenoid alkaloids in the Chinese species and of their biogenetic pathways. The correlation between phylogeny, chemical constituents and pharmaceutical uses in the genus Aconitum is also discussed from the data of the toxicity and therapeutic value of the species in the genus, a research field for which the term ＂pharmacophylogenetics＂ is here specifically coined. The major points of the paper are summarized as follows： 1. Diterpenoid alkaloids known in plants fall into four skeletal types： C18, C19, C20 and bisditerpenoid alkaloids. They can be further subdivided into 14 subgroups, namely, C18： appaconine-type （Ⅰ） and ranaconine-type （Ⅱ）; C19： aconitine-type （Ⅲ）, lycoctonine-type （Ⅳ）, 7,17-seco-type （Ⅴ） and lactone-type （Ⅵ）; C20： atisine-type （Ⅶ）, denudatine-type （Ⅷ）, hetidine-type （Ⅸ）, hetisine-type （Ⅹ）, veatihine-type （Ⅺ） （not found in Aconitum species）, napelline-type （Ⅻ） and anopterine-type （ⅩⅢ） （not found in Aconitum species）; and bisditerpenoid alkaloids （ⅩⅣ）. 2. The species in Aconitum subgen. Lycoctonum contain mainly the C18-diterpenoid alkaloids （lappaconine-type and ranaconine-type） and C19-diterpenoid alkaloids （lycoctonine-type）. Roots of the plants in this subgenus show a relatively lower toxicity （LD50 to mice=1660-3340 mg/kg （i.v.）） and have been used for the treatment of rheumatism, pains and irregular menstruation etc. Because of the lower toxicity of the roots, the species in this subgenus are worthy a more detailed phytochemical investigation for the development of new medicines. 3. Aconitum subgen. Aconitum is the largest subgenus, with about 250 species which are usually divided into two sections, section Sinaconitum, a monotypic section including only A. polycarpum, and section Aconitum including the remaining species. The species in China in the latter section are usually divided into nine series. （1）. Series Tangutica and series Rotundifolia are all dwarf alpine plants, generally less than 35 cm tall. Phytochemically, they contain mainly the lactone-type C19-diterpenoid alkaloids and sporadically C20-diterpenoid alkaloids. The lactone-type alkaloids have been found so far to occur exclusively within these two series, and thus can be considered as the characteristic chemical constituents of these two series. The roots in the plants of the two series show a relatively lower toxicity （LD50 to mice =ca. 2400 mg/kg （i.v.））. The whole plants of the species have been traditionally used in China＇s Tibetan, Mongolian and Uygur regions for the treatment of high fever. （2）. The species in series Bullatifolia contain mainly the denudatine-type and the napelline-type C20-diterpenoid alkaloids, and the aconitine-type C19-diterpenoid alkaloids. This series may occupy a somewhat intermediate position in Aconitum subgen. Aconitum from a chemotaxonomic view. In toxicity, the LD50 to mice range from 210-270 mg/kg （i.v.）. The roots in this series have been used for the treatment of pains and rheumatism. （3）. Series Brachypoda includes A. brachypodum, A. pendulum, A. polyschistum and several other morphologically very similar species. Their roots are recorded as ＂Xue-shang-yi-zhi-hao＂ in the Chinese Materia Medica and have been used as anti-rheumatic and analgesic remedies. Phytochemically, they contain mainly the aconitine-type C19-diterpenoid alkaloids, an evolutionarily advanced type. The LDso to mice range from 130-280 mg/kg （i.v.）. It is noteworthy that A. coreanum contains mainly the C20-diterpenoid alkaloids and has a much lower toxicity （LD50 = 2800 mg/kg （i.v.） to mice） than the other species in this series. From a chemotaxonomic view it seems reasonable to segregate A. coreanum and its closet ally, A. anthoroideum, from series Brachyloda to establish an independent series. （4）. Series Stylosa, with plants generally of larger roots, are the major sources of ＂Da-wu-tou＂. The species in the series contain mainly the aconitine-type diester C19-diterpenoid alkaloids, which are characterized by the presence of anisoyloxy residues at C-14. The roots display a high toxicity with the LDso to mice ranging from 24-102 mg/kg （i.v.）. From a chemootaxonomic view, A. contortum, mainly with the presence of the hetidine-type C20-diterpenoid alkaloids and the dranaconine-type C18-diterpenoid alkaloids and yet the absence of anisoyloxy residues, seems to be a very special species in series Stylosa. Its systematic position needs to be reconsidered. （5） Series Ambigua, eight species of which have been investigated phytochemically, contains mainly the aconitine-type C19-diterpenoid alkaloids with anisoyloxy residues, indicating its close affinity to series Stylosa. （6）. Series Volubilia, which is characterized by having twining stems, contains the aconitine-type diester C19-diterpenoid alkaloids with the presence of an anisoyl or a benzoyl group at C-14. Several species in this series, such as A. sczukinii and A. volubile, contain the highly advanced 15-hydroxyl aconitine-type Ci9-diterpenoid alkaloids, indicating its possible affinity to series Inflata. The LDso to mice range from 84-283 mg/kg （i.v.）. The roots of many species in this series have been used as folklore drugs for the treatment of trauma and rheumatic pains. In this series, A. hemsleyanum, a very polymorphic species in gross-morphology, exhibits also a greatinterpopulational phytochemical variation. （7）. Series Inflata includes the two most widely medicinally used Aconitum species, A. carmichaeli and A. kusnezoffii. Both are now officially listed in the Chinese pharmacopoeia. They contain the aconitine-type 15-hydroxyl monoester or diester C19-diterpenoid alkaloids, highly advanced chemical constituents in the genus Aconitum. The LD50 to mice range from 66-137 mg/kg （i.v.）. The cardiovascular, muscle-smoothing and central effects of the two species have been thoroughly studied. （8）. Series Grandituberosa, which is morphologically characterized by having several chain-like arranged tubers, contains the highly advanced aconitine-type C19-diterpenoid alkaloids. The roots, with the LD50 to mice being 29 mg/kg （i.v.）, have a high toxicity. （9）. Series Racemulosa, with only A. racemulosum var. pengzhouense phytochemically already studied in detail and from it a novel skeleton of C20-diterpenoid alkaloids, i.e. racemulosine, being found, shows extraordinary chemical features. It contains mainly, however, the lycoctonine-type and the aconitine-type amino alcohol C19-diterpenoid and C20-diterpenoid alkaloids. The roots of A. racemulosum are known as ＂Xue-Wu＂ and have the actions of activating blood circulation and removing stasis. From a chemotaxonomic view, this series show some primitive features. （10）. Series Brunnea is phytochemically not well known. This series contains both C20-diterpenoid alkaloids, e.g. denudatine and songorine, and the highly advanced aconitine-type alkaloids, indicating its intermediate position between the series Bullatifolia and the series Brachypoda. 4. The monotypic subgenus Gymnaconitum, with only A. gymnandrum, is of both primitive and advanced features phytochemically and gross-morphologically. The whole plant of this species is used as insecticide. In summary, 76 Aconitum species in China have been medicinally used. They are mainly used for the treatment of plaque, sepsis, intoxic