Issue in Honor of Prof. Atta-ur-Rahman ARKIVOC 2007 (vii) 265-272
browniine in our study showed a lesser amount of cytotoxicity on MDBK and Vero cell lines at 64 µg/ml. Gonzales-Coloma et al.11 studied antifeedant activity and toxicity of some diterpene alkaloids (15-acetylcardiopetamine, cardiopetamine along with its amino alcohol, the beta, gamma unsaturated ketone, and the acetylated ketone derivatives) from Delphinium sp. on the insects Spodoptera littoralis and Leptinotarsa decemlineata. The results of the study showed that the C13 and C15 hydroxy substituents are essential features of the active molecule, while the C11 benzoate group enhanced the biological effect on both insect species for their structureactivity relationship, where all of our alkaloids lacked of those two substituents.
In a taxonomic study12, lycoctonine-type of alkaloids isolated from three Delphinium species were classified into three groups according to the degree of their toxicity as N-(methylsuccinyl)anthranoyllycoctonine (MAL)-type with high toxicity, lycoctonine-type with moderate toxicity, as well as 7,8-methylene-dioxylycoctonine (MDL)-type with low toxicity. In that paper, it was reported that the moiety attached to C14 is quite important for the toxicity of these alkaloids, which is also consistent with our present data. Furthermore, other functionalities on these molecules are also notable in terms of toxicity. It was found that the tertiary nitrogen, anthranilic acid substitution, and C1 moiety affects the toxicity degree within those alkaloids. For instance; when the methylsuccinyl group is removed from MAL (which then converts to lycoctonine), lycoctonine becomes 93 times less toxic.
Additionally, there is one report on antimicrobial activity of the methanolic extracts of two Consolida species of Iranian origin.13 According to the data they obtained; C. orientalis was significantly active against B. subtilis and Morganella morganii, while C. rugulosa showed a worth-mentioning inhibition towards E. coli and C. albicans. Without any doubt, the difference between their antimicrobial activities could be due to different phytochemical content, particularly in conjunction with their diterpene alkaloidal compounds.
Even though much is already known about toxicity of diterpene alkaloids that contribute to the toxicity of Consolida, Delphinium, and Aconitium species, no antiviral study has been so far reported on these-type alkaloids hitherto. Moreover, it is worth highlighting one of our past screening studies which described the antiviral effect of C. hellespontica against Sindbis virus and HSV.14 Interestingly, 50% ethanolic extract prepared from this plant did not exert any inhibition in those tests. For that reason, the alkaloids from Consolida in our study were also completely inactive against HSV.
Our results showed that the alkaloids (1-5) possess rather high antifungal activity against C. albicans and a compelling antibacterial effect only against K. pneumoniae and A. baumannii, while they exert a strong inhibition against PI-3. This is the first report of antiviral, antibacterial, and antifungal activities of lycoctonine, 18-O-methyllycoctonine, delcosine, 14-acetyldelcosine, and 14-acetylbrowniine. Furthermore, our data also suggest that all of the diterpene alkaloids are worthy of being evaluated in regard to their antimicrobial and antiviral activities for promising results.
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