直立百部的一个新异名

根据对直立百部Stemona sessilifolia（Miq．）Miq．大量标本的研究和野外调查及引种栽培观察,结合对山东百部Stemona shandongensis D．K．Zang模式标本产地的调查,发现直立百部的形态性状是多变的。研究表明它的习性受生境影响而多变,从直立半灌木到蔓生都有;叶型多变;花通常出自叶腋,而花梗有时与叶柄,甚至主脉合生;内轮花被片大多明显大于外轮。山东百部的形态性状处于直立百部的变异范围内,因此作为独立的种是难以成立的,应处理为直立百部的新异名。     

中国植物区系新资料

该文报道了发现于云南盈江的2个中国植物新分布属——木瓜桐属（Siphonodon Griff.）和羽脉百部属（Stichoneuron Hook. f.）,以及对应的2个新记录种木瓜桐（Siphonodon celastrineus Griff.）和羽脉百部（Stichoneuron membranaceum Hook.f.）,并结合原始文献及野外调查对其形态特征进行了详细描述。凭证标本存放于中国科学院西双版纳热带植物园标本馆（HITBC）。     

Insecticidal pyrido[1,2-a]azepine alkaloids and related derivatives from Stemona species

Eight new alkaloids, the pyrido[1,2-a]azepines stemokerrin, methoxystemokerrin-N-oxide, oxystemokerrin, oxystemokerrin-N-oxide, and pyridostemin, along with the pyrrolo[1,2-a]azepines dehydroprotostemonine, oxyprotostemonine, and stemocochinin were isolated from four Stemona species together with the known compounds protostemonine, stemofoline, 2'-hydroxystemofoline, and parvistemonine. Their structures were elucidated by 1H and 13C NMR including 2D methods and two key compounds additionally by X-ray diffraction. Besides the formation of a six membered piperidine ring, additional oxygen bridges and N-oxides contributed to structural diversity. The co-occurrence of pyrrolo- and pyridoazepines suggested biosynthetic connections starting from more widespread protostemonine type precursors. Bioassays with lipophilic crude extracts against Spodoptera littoralis displayed very strong insecticidal activity for the roots of S. curtisii and S. cochinchinensis, moderate activity for S. kerrii, but only weak effects for the unidentified species HG 915. The insect toxicity was mainly caused by the accumulation of stemofoline, oxystemokerrin, and dehydroprotostemonine displaying two different modes of action. Based on the various insecticidal activities of 13 derivatives structure-activity relationships became apparent.     

Two Stemona alkaloids from Stemona sessilifolia (Miq.) Miq.

Two new alkaloids, named dehydrostenine A (1) and B (2), were isolated from the roots of Stemona sessilifolia (Miq.) Miq. Their structures were elucidated by comprehensive NMR spectroscopy and X-ray single-crystal diffraction experiment. Anti-acetylcholinesterase activities of compounds 1 and 2 were also tested, but did not show significant activity.     

Pyrrolo- and pyridoazepine alkaloids as chemical markers in Stemona species

Broad-based phytochemical investigations on 31 Stemona species and geographical provenances led to an overview concerning characteristic accumulation trends and the distribution of different Stemona alkaloids. Two major metabolic differences suggested a taxonomic segregation of the complex Stemona tuberosa group from the other species, and was supported by morphological characters. Whereas most of the Stemona species were characterised by protostemonine type alkaloids, the S. tuberosa group clearly deviated by accumulation trends towards tuberostemonine or croomine derived alkaloids belonging to two different skeletal types. Also of chemotaxonomic relevance was the structural divergence of protostemonine type alkaloids into pyrrolo- or pyridoazepine derivatives represented by stemofoline or oxystemokerrine, respectively, as major constituents. Their common occurrence in different provenances of S. curtisii, also deviating from the other species by various chromosome numbers, deserves special taxonomic attention. Species specific chemical markers were given by the unique accumulation of didehydrostemofoline (=asparagamine A) in S. collinsae and stemokerrine in S. kerrii. In contrast to previous reports, no bisdehydro derivatives with an aromatic pyrrole ring were detected supporting the hypothesis that these alkaloids are artifacts. A new stereoisomer of tuberostemonine was isolated and identified by spectroscopic methods.     

Antibacterial stilbenoids from the roots of Stemona tuberosa

Twelve dihydrostilbenes, stilbostemins N-Y (1-12), and a phenanthraquinone, stemanthraquinone (13), were isolated and identified from roots of Stemona tuberosa, along with five known dihydrostilbenes. Their structures were established on the basis of 1D and 2D NMR and other spectroscopic analyses. Dihydrostilbene 8 exhibited strong activity against Bacillus pumilus (MIT 12.5-25 microg/mL). Many tested compounds exhibited moderate antibacterial activities.     

Dihydrophenanthrenes and other antifungal stilbenoids from Stemona cf. pierrei

Three new dihydrophenanthrenes, stemanthrenes A-C, along with the new dihydrostilbene stilbostemin G were isolated and identified from the underground parts of Stemona cf. pierrei together with the known pinosylvin, 4'-methylpinosylvin, dihydropinosylvin, stilbostemins B, D, and E as well as the pyrrolo[1,2-a]azepine alkaloids protostemonine and stemonine. The structures of all new stilbenoids, elucidated by NMR analyses, showed a common substitution pattern for aromatic ring A and characteristic C-methylations for ring B. The trivial name racemosol, previously reported for S. collinsae, was renamed to stemanthrene D due to its priority for another compound. Bioautographic tests on TLC plates with Cladosporium herbarum displayed high antifungal activity for compounds with an unsubstituted aromatic ring A, e.g. pinosylvin, but only weak effects for the higher substituted stilbostemin G and stemanthrenes A-C. Similar results were obtained by germ tube inhibition of five microfungi using 2-fold serial broth dilutions determined by a microplate reader. Because of weak inhibition and chemical instability of stemanthrenes, no EC(50) and EC(90) values could be calculated.     

Furfural Derivatives and Phenolic Constituents in Stemona tuberosa Lour

Chemical investigation on the water-soluble constituents of Stemona tuberosa Lour. resulted in the isolation of a previously undescribed furfural derivative namely (S)-5-((R)-hydroxy(5-(hydroxymethyl)furan-2-yl)methyl)-5-methylfuran-2(5H)-one and twenty-five known compounds from the water decoction of the dried root tubers. Their structures were determined by analysis of the extensive spectroscopic data, including 1D/2D NMR, HR-ESI-MS, and ORD, as well as the ECD simulation and comparison. Most of them were phenolic and among them, four compounds were isolated from Stemona plants for the first time. This study uncovers diverse constituents from water decoction of S. tuberosa dedicated for its quality control and allows for the exploitation of chemical markers with potential significance for discrimination of Stemona plants.     

Isolation and chemotaxonomic significance of tuberostemospironine-type alkaloids from Stemona tuberosa

An alkaloid named 6alpha-hydroxycroomine (1) as well as the known croomine (2), both belonging to the tuberostemospironine-alkaloid type, were isolated from Stemona tuberosa as the major components. The structure of 1 was elucidated through extensive spectroscopic analyses. Comparison of the HPLC profiles of the total alkaloids and the crude methanol extract showed that both compounds are naturally occurring. The first isolation of 1 and 2 from S. tuberosa has chemotaxonomic significance, confirming the close relationship between Stemona and Croomia. The trnL sequences of plants from the four genera of Stemonaceae cluster together as a clade, further lending support to retaining them in a single family.