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Monoterpenoid indole alkaloids are structurally diverse natural products found in plants of the family Apocynaceae. Among them, vincristine and its derivatives are well known for their anticancer activity. Bousigonia mekongensis, a species in this family, contains various monoterpenoid indole alkaloids. In the current study, fourteen known aspidosperma-type monoterpenoid indole alkaloids (1–14) were isolated and identified from a methanol extract of the twigs and leaves of B. mekongensis for the first time. Among them, compounds 3, 6, 9, and 13 exhibited similar antiproliferative activity spectra against A549, KB, and multidrug-resistant (MDR) KB subline KB-VIN cells with IC50 values ranging from 0.5–0.9 μM. The above alkaloids efficiently induced cell cycle arrest at the G2/M phase by inhibiting tubulin polymerization as well as mitotic bipolar spindle formation. Computer modeling studies indicated that compound 7 likely forms a hydrogen bond (H-bond) with α- or β-tubulin at the colchicine site. Evaluation of the antiproliferative effects and SAR analysis suggested that a 14,15-double bond or 3α-acetonyl group is critical for enhanced antiproliferative activity. Mechanism of action studies demonstrated for the first time that compounds 3, 4, 6, 7, and 13 efficiently induce cell cycle arrest at G2/M by inhibiting tubulin polymerization by binding to the colchicine site. [ABSTRACT FROM AUTHOR]

Ten alkaloids ( 1 – 10 ), with sophoridine ( 1 ) as the most abundant component, were obtained from the whole plants of Oxytropis ochrocephala Bunge. Furthermore, eight new sophoridine derivatives ( 11 – 16 , 20 , 21 ), with modification on the C-14 position of 1 were synthesized. All compounds ( 1 – 16 , 20 , 21 ) were evaluated for antiproliferative activity against five human tumor cell lines. Among them, the newly synthesized derivative 20 exhibited the best inhibitory activity against the tested cell lines. Its activity was increased by more than fourfold as compared with parent compound 1 . [ABSTRACT FROM AUTHOR]

The new quinolizidine alkaloid (+)-(14β)-14-ethylmatridin-15-one (I) is isolated from the poisonous plant Oxytropis ochrocephala. [ABSTRACT FROM AUTHOR]

Ten known alkaloids are isolated from Oxytropis ochrocephala with sophoridine (I) as the most abundant component. [ABSTRACT FROM AUTHOR]

Little information has been reported on the antitumor effects of the diterpenoid alkaloid constituents of Aconitum plants, used in the herbal drug ‘bushi’. This study was aimed at determining the antitumor activities of Aconitum C 19 -and C 20 -diterpenoid alkaloids and synthetic derivatives against lung (A549), prostate (DU145), nasopharyngeal (KB), and vincristine-resistant nasopharyngeal (KB-VIN) cancer cell lines. Newly synthesized C 20 -diterpenoid alkaloid derivatives showed substantial suppressive effects against all human tumor cell lines tested. In contrast, natural and derivatized C 19 -diterpenoid alkaloids showed only a slight or no effect. Most of the active compounds were hetisine-type C 20 -diterpenoid alkaloids, specifically kobusine and pseudokobusine analogs with two different substitution patterns, C-11 and C-11,15. Notably, several C 20 -diterpenoid alkaloids were more potent against multidrug-resistant KB subline KB-VIN cells. Pseudokobusine 11-3′-trifluoromethylbenzoate ( 94 ) is a possible promising new lead meriting additional evaluation against multidrug-resistant tumors. [ABSTRACT FROM AUTHOR]