Solis Gonzalez, Pablo Narciso; (1994) Bioactive principles from Panamanian medicinal plants. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Plants are widely used in Panama and Central America to cure different diseases, including malaria and amoebic dysentery. Cephaëlis ipecacuanha of the family Rubiaceae contains emetine, which is used in the treatment of severe amoebic dysentery. Species of Rubiaceae, Simaroubaceae, Meliaceae and Menispermaceae have been examined, they are known to contain isoquinoline alkaloids, quassinoids, limonoids and bisbenzyiisoquinoline (bbiq) alkaloids, respectively, with activity against Plasmodium falciparum. In order to obtain antiprotozoal natural products such as quassinoids, limonoids, bbiq's and emetine related alkaloids it was decided to investigate the following plants: Guarea macropetala, G. rhopalocarpa, Ruagea glabra (Meliaceae); Abuta dwyerana (Menispermaceae); Cephaëlis camponutans, C. dichroa, C. dimorphandrioides, C. glomerulata, Lasianthus panamensis (Rubiaceae); Picramnia antidesma subsp. fessonia, P. teapensis (Simaroubaceae). Extracts from different parts of the plants were fractionated and tested against brine shrimp and KB cells. Four plants were chemically studied and the isolated compounds were characterized by mass spectra, infrared, ultraviolet, 1H and 13C NMR, also, two dimensional NMR experiments such as COSY-45, HMQC, HMBC and ROESY. Circular dichroism was used to establish the absolute configuration of some of the compounds. C. camponutans yielded benz[g]isoquinoline-5,10-dione, isolated for the first time from the plant kingdom, and a the new 1-OH- benzoisochromanquinone. Both compounds showed activity against brine shrimp, KB cells and Plasmodium falciparum, in vitro. C. dichroa yielded six indole monoterpenoid alkaloids, including strictosidine, strictosamide, angustine, vallesiachotamine, iso-vallesiachotamine and the novel vallesiachotamine lactone. In contrast, C. glomerulata yielded three new quinoline alkaloids, named, glomerulatine A, B and C. The taxonomic position of Cephaëlis is unclear and more detailed information on the constituent alkaloids may prove valuable in unravelling this problem. The butanolic fraction from de leaves of P. antidesma subsp. fessonia, showed strong activity against KB cells and yielded two known anthraquinones (aloe-emodin, aloe-emodinanthrone) and three new C-glycoside of aloe-emodin, named picramnioside A, B and C. The C-glycosides showed activity against KB cells. A cytotoxic microwell test using Artemia salina (brine shrimp) was developed in order to overcome some of the disadvantages of the previously described method. The test was predictive of cytotoxicity and compounds with activity on the nervous system were inactive. The activity of the quassinoids against KB cell and P. falciparum parallel the activity against brine shrimp.

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