Effects of alkaloids from Aconitum yesoense var. macroyesoense on cutaneous blood flow in mice

Pd-Catalyzed Stereoselective Construction of Benzo-Fused Decalines with a Quaternary Carbon

The Pd-catalyzed stereoselective construction of decalins with one-carbon units bearing heteroatoms at the ring junction is described. The Pd-catalyzed cyclization of silyl enol ether resulted in exclusive formation of the cis isomer (89%, >100/1 cis/trans). On the contrary, Pd-catalyzed carboiodination and carboborylation (with oxidative workup) provided products in 56% yield (1/>100 cis/trans) and 69% yield (1/11 cis/trans), respectively.

Chemistry and biological activities of hetisine-type diterpenoid alkaloids

Hetisine-type C₂₀-diterpenoid alkaloids (DAs) are one of the most important DA subtypes. During the past decades, a total of 157 hetisine-type DAs were obtained from plants from seven genera in three families, most of which were isolated from the genera Aconitum and Delphinium in the Ranunculaceae family. Structurally, hetisine-type DAs are characterized by a heptacyclic hetisane skeleton formed by the linkage of C(14)–C(20) and N–C(6) bonds in an atisine-type DA, and their structural diversity is created by the states of the N atom and various substituents. Pharmacological studies have revealed a wide range of pharmacological actions for hetisine-type DAs, including antiarrhythmic, antitumor, antimicrobial and insecticidal activities, as well as effects on peripheral vasculature, which are closely related to their chemical structures. In particular, the prominent antiarrhythmic effects and low toxicity of hetisine-type DAs highlight their potential in antiarrhythmic drug discovery. Hetisine-type DAs with diverse bioactivities are promising lead structures for further development as commercial agents in medicine.

Natural hetisine-type C₂₀-diterpenoid alkaloids with diverse structures showed multiple pharmacological activities, indicating great potential in drug discovery.

Cytotoxic Effects of Diterpenoid Alkaloids Against Human Cancer Cells

Diterpenoid alkaloids are isolated from plants of the genera Aconitum, Delphinium, and Garrya (Ranunculaceae) and classified according to their chemical structures as C18-, C19- or C20-diterpenoid alkaloids. The extreme toxicity of certain compounds, e.g., aconitine, has prompted a thorough investigation of how structural features affect their bioactivities. Therefore, natural diterpenoid alkaloids and semi-synthetic alkaloid derivatives were evaluated for cytotoxic effects against human tumor cells [A549 (lung carcinoma), DU145 (prostate carcinoma), MDA-MB-231 (triple-negative breast cancer), MCF-7 (estrogen receptor-positive, HER2-negative breast cancer), KB (identical to cervical carcinoma HeLa derived AV-3 cell line), and multidrug-resistant (MDR) subline KB-VIN]. Among the tested alkaloids, C19-diterpenoid (e.g., lipojesaconitine, delcosine and delpheline derivatives) and C20-diterpenoid (e.g., kobusine and pseudokobusine derivatives) alkaloids exhibited significant cytotoxic activity and, thus, provide promising new leads for further development as antitumor agents. Notably, several diterpenoid alkaloids were more potent against MDR subline KB-VIN cells than the parental drug-sensitive KB cells.

Structure-activity relationships and evaluation of esterified diterpenoid alkaloid derivatives as antiproliferative agents

Diterpenoid alkaloids with remarkable chemical properties and biological activities are frequently found in plants of the genera Aconitum, Delphinium, and Garrya. However, little information has been reported on the antiproliferative effects of the diterpenoid alkaloid constituents of Aconitum and Delphinium plants. C-1 and 14 esterifications of delcosine (1) were carried out to provide 39 new diterpenoid alkaloid derivatives (3-14, 16-29, 3a-7a, 9a, 13a, 13b, 14a, 14b, 16a, 17a, 24a, 35a). Selected compounds (3-14, 16-29, 3a-7a, 9a, 13a, 13b, 14a, 14b, 16a, 17a, 24a, 35a) were evaluated for antiproliferative activity against three to five human tumor cell lines including triple-negative breast cancer (TNBC) and P-glycoprotein (P-gp) overexpressing multidrug-resistant (MDR) subline. Several newly synthesized delcosine derivatives (6, 7, 13, 13a, 13b) showed substantial suppressive effects against all human tumor cell lines tested. In contrast, the natural alkaloids (1, 31, 33) showed no effect. Most of the active compounds were delcosine derivatives with two specific substitution patterns-C-1 and C-1,14. In particular, 1-acyldelcosine derivative (5-7) displayed more potency than 1,14-diacyldelcosine derivatives (5a-7a). These acylated alkaloid derivatives caused accumulation of TNBC cells at sub-G1 within 24 h. 1-Acylation of 1 appears to be critical for producing antiproliferative activity in this alkaloid class and a means to provide promising new leads for further development into antitumor agents.

Evaluation of Aconitum diterpenoid alkaloids as antiproliferative agents

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 C19-and C20-diterpenoid alkaloids and synthetic derivatives against lung (A549), prostate (DU145), nasopharyngeal (KB), and vincristine-resistant nasopharyngeal (KB-VIN) cancer cell lines. Newly synthesized C20-diterpenoid alkaloid derivatives showed substantial suppressive effects against all human tumor cell lines tested. In contrast, natural and derivatized C19-diterpenoid alkaloids showed only a slight or no effect. Most of the active compounds were hetisine-type C20-diterpenoid alkaloids, specifically kobusine and pseudokobusine analogs with two different substitution patterns, C-11 and C-11,15. Notably, several C20-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.

Structure-activity relationships and the cytotoxic effects of novel diterpenoid alkaloid derivatives against A549 human lung carcinoma cells

The cytotoxicity of three alkaloids from the roots of Aconitum yesoense var. macroyesoense as well as 36 semi-synthetic C(20)-diterpenoid atisine-type alkaloid derivatives against A549 human lung carcinoma cells was examined. Ten acylated alkaloid derivatives, pseudokobusine 11-veratroate (9), 11-anisoate (12), 6,11-dianisoate (14), 11-p-nitrobenzoate (18), 11,15-di-p-nitrobenzoate (22), 11-cinnamate (25) and 11-m-trifluoromethylbenzoate (27), and kobusine 11-p-trifluoromethylbenzoate (35), 11-m-trifluoromethylbenzoate (36) and 11,15-di-p-nitrobenzoate (39), exhibited cytotoxic activity, and 11,15-dianisoylpseudokobusine (16) was found to be the most potent cytotoxic agent. Their IC(50) values against A549 cells ranged from 1.72 to 5.44 μM. In the occurrence of cytotoxic effects of atisine-type alkaloids, replacement by an acyl group at both C-11 and C-15 resulted in the enhancement of activity of the parent alkaloids compared to that from having hydroxy groups at this position, and the presence of a hydroxy group at the C-6 position was required for the cytotoxic effects. These acylated alkaloid derivatives inhibit cell growth through G1 arrest.

Inhibitory effects of diterpenoid alkaloids on the growth of A172 human malignant cells

The cytotoxicity against A172 human malignant glioma cells was examined for 14 alkaloids from the roots of Aconitum yesoense var. macroyesoense and of Aconitum japonicum and from the seeds of Delphinium elatum as well as for 25 semisynthetic derivatives. The major alkaloid constituents of A. yesoense var. macroyesoense, kobusine (2) and pseudokobusine (3), a minor alkaloid constituent of A. japonicum, aljesaconitine A (5), and six alkaloid derivatives, N-deethyldelcosine (10), N-deethyldelsoline (11), 12-benzoylluciculine (18), 12-anisoylluciculine (19), 6,11-dibenzoylpseudokobusine (28), and 6-veratroylpseudokobusine (29), had only very weak activity. Four acylated alkaloid derivatives, 12-acetylluciculine (23), 11-veratroylpseudokobusine (30), 11-(m-trifluoromethylbenzoyl)pseudokobusine (32), and 11-(m-trifluoromethylbenzoyl)kobusine (39), exhibited more potent activity, while pseudokobusine 11-cinnamoate (31), 11-anisoate (33), and 11-p-nitrobenzoate (34) were found to be the most potent cytotoxic agents.

Enantioselective approach to the hetisine alkaloids. Synthesis of the 3-methyl-1-aza-tricyclo[5.2.1.0(3,8)]decane core via intramolecular dipolar cycloaddition

[structure: see text]. An efficient, enantioselective approach to the hetisine class of the C(20)-diterpenoid alkaloids is described. The strategy involves an intramolecular oxidopyridinium dipolar cycloaddition as the key transformation, in which simultaneous formation of the C5-C6 and C10-C20 bonds in the 3-methyl-1-aza-tricyclo[5.2.1.0(3,8)]decane core of the hetisine alkaloids is effected.

[Studies on structural elucidation of Aconitum diterpenoid alkaloid by LC-APCI-MS and effects of Aconitum diterpenoid alkaloid on cutaneous blood flow]

The chemical constituents of Aconitum yesoense var. macroyesoense and Aconitum japonicum were examined using high-resolution spectral analysis. Twelve novel alkaloids were isolated from A. yesoense var. macroyesoense together with 20 known alkaloids. Eight novel alkaloids were isolated from A. japonicum together with 15 known alkaloids. An HPLC-atmospheric pressure chemical ionization-mass spectrometry (HPLC-APCI-MS) method was useful for the simultaneous determination of 21 Aconitum alkaloids found in A. yesoense var. macroyesoense and A. japonicum. These compounds were fairly stable under the conditions used, and the protonated molecules or fragment ions characteristic of the molecule appeared as base peaks in the mass spectra and were used for selected ion monitoring. HPLC-APCI-MS is a very promising approach for structural investigations of positional isomers and stereoisomers. This method was applied successfully to stereoisomeric Aconitum alkaloids differing in configuration at C-1, -6, or -12. Comparison of the APCI spectra showed that the abundance of fragment ions was significantly higher for the C-1, -6, or -12 beta-form alkaloid than for C-1, -6, or -12 alpha-form alkaloid. The main alkaloid constituents in the root of A. yesoense var. macroyesoense, Aconitum alkaloids of the C20-diterpenoid type, kobusine and pseudokobusine, and their acyl derivatives were examined for their peripheral vasoactivities by measuring laser-flowmetrically the cutaneous blood flow in the hind foot of mice after intravenous administration. It is thought that the hydroxyl groups of alkaloids, especially a free OH group of pseudokobusine at C-6, were important for action on the peripheral vasculature leading to dilatation, and the results indicated that esterification of the hydroxyl group at C-15 with either anisoate, veratroate, or p-nitroben-zoate may contribute to enhancement of the activity of the parent alkaloids.