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Protostemonamide ( 1), a new protostemonine-type alkaloid, and 12 known compounds were isolated from the roots of Stemona sessilifolia. Their structures were elucidated by 1 D and 2 D NMR spectral and other spectroscopic studies. The main alkaloidal constituents, protostemonine ( 2), stemospironine ( 4), and maistemonine ( 7), showed significant antitussive activity in a citric acid-induced guinea pig cough model following peripheral administration; stemonamine ( 11) had antitussive activity following i. c. v. administration.

Investigation of the roots of Stemona tuberosa afforded five minor constituents, stemoenonine (1), 9a- O-methylstemoenonine (2), oxystemoenonine (3), 1,9a- seco-stemoenonine (4), and oxystemoninine (5), along with the known compound stemoninoamide (6). Their structures were elucidated by 1D and 2D NMR spectra and other spectroscopic studies. Alkaloids 1, 2, and 6, as well as the representative stemoninine-type alkaloid, stemoninine (7), were screened for antitussive activity in the citric acid-induced guinea pig cough model. Compounds 6 and 7 exhibited strong antitussive activity after oral and intraperitoneal administrations.

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.

Five new alkaloids, 6beta-hydroxystemofoline (1), 16-hydroxystemofoline (2), neostemofoline (3), protostemodiol (4), and 13-demethoxy-11(S*),12(R*)-dihydroprotostemonine (5), along with 10 known alkaloids, were isolated from stems and leaves of Stemona japonica. Their structures were elucidated by 1D and 2D NMR and other spectroscopic studies. The insecticidal activity of the agonist 16-hydroxystemofoline (2) and antagonist 13-demethoxy-11(S*),12(R*)-dihydroprotostemonine (5) was demonstrated by electrophysiological in vitro tests on the insect nicotinic acetylcholine receptor and by in vivo screenings against relevant agricultural insect pests.

Two new bisbenzopyrans, namely 3,3'-bis(3,4-dihydro-4-hydroxy-6,8-dimethoxy-2H-1-benzopyran) (1), and 8'-methoxy-3,3'-bis(3,4-dihydro-4-hydroxy-6-methoxy-2H-1-benzopyran) (2), together with known 3,3'-bis(3,4-dihydro-4-hydroxy-6-methoxy-2H-1-benzopyran) (3), as well as three known pyrido[1,2-alpha]azapine alkaloids, stemokerrin (4), oxystemokerrin (5) and oxystemokerrin-N-oxide (6), were isolated and identified from the roots of Stemona cochinchinensis. The structures of these compounds were elucidated by 1D- and 2D-NMR spectra and other spectroscopic studies.

Five new Stemona alkaloids, cochinchistemoninone (1), stemokerrin-N-oxide (2), oxystemokerrilactone (3), saxorumamide (4a), and isosaxorumamide (4b), as well as 12 known compounds, were isolated from the roots of Vietnamese Stemona saxorum. The structures of these alkaloids were characterized on the basis of spectroscopic methods.

Two new dihydrostilbenes, stilbostemins H (1), I (2), and a new dihydrophenanthrene, stemanthrene E (3), were isolated and identified from the roots of Stemona sessilifolia, together with known stilbostemins B, D and G, and stemanthrenes A and C (4-8). Structures of new stilbenoids were established by 1D and 2D (1)H NMR and (13)C NMR spectroscopic analyses.

Five new stemoninine-type alkaloids, bisdehydrostemoninine (1), isobisdehydrostemoninine (2), bisdehydroneostemoninine (3), and bisdehydrostemoninines A (4) and B (5), were isolated from the crude-alkaloid extract of the roots of Stemona tuberosa. Their structures were elucidated on the basis of one- and two-dimensional NMR and other spectroscopic studies. The relative configuration of 4 was determined by X-ray diffraction. Alkaloid 1 displayed significant antitussive activity in the citric acid-induced guinea pig cough model.

Three new dihydrostilbenes, stilbostemins J-L (1-3), and a new dihydrophenanthrene, stemanthrene F (4), were isolated from the roots of Stemona japonica together with two known bibenzyls, 3,5-dihydroxy-4-methylbibenzyl (5) and 3,5-dihydroxy-2'-methoxy-4-methylbibenzyl (6). Their structures were elucidated by spectroscopic analyses. Compounds 3-6 exhibited strong antibacterial activities against Staphylococcus aureus and Staphylococcus epidermidis.