|Tesis Doctorales de la Universidad de Alcalá
|ISOLATION AND DESIGN OF DITERPENOIDS FROM PLECTRANTHUS SPECIES
|Ntungwe , Epole Ngolle
|Biología de Sistemas
|Dias de Mendonça Rijo, Patricia
|Díaz Lanza, Ana María
|Fecha de defensa
|Sobresaliente Cum Laude
|Ciencias de la Salud (RD 99/2011)
|The HPLC analysis of P. hadiensis leaves showed that the known abietane diterpene, 7¿-acetoxy-6ß-hydroxyroyleanone (Roy) was the major compound in this extract. Roy was isolated and tested against the aggressive type of triple-negative breast cancer (MDA-MB-231S) cell lines. P. hadiensis extract and Roy reduced the viability of MDA-MB-231S cancer cell lines, showing an IC50 value of 25.6 µg/mL and 5.5 µM (2.15 µg/mL) respectively, suggesting that this lead molecule could be responsible for the bioactivity of this extract.
Due to the poor aqueous solubility of royleanones, the need to decrease the site effects and enhance a target drug delivery; Roy, its hemisynthetic derivative 7¿-acetoxy-6ß-benzoyloxyroyleanone (12BzRoy) and 6,7-dehydroroyleanone (DHR) isolated from the essential oil of P. madagascariensis were used as lead molecules for the synthesis of self-assembled nanoparticles. Squalene (Sq), Oleic acid (OA) and 1-bromodecane were used was linkers. Roy-OA, DHR-sq, and 12BzRoy-sq conjugates were successfully synthesized and their nanoassemblies characterized based on size, Pdl, zeta potential, and morphology. The release profile of Roy was determined from Roy-OA NPs at physiological pH 7.4. The biological activity of DHR.sq and, Roy-OA NPs were evaluated, and both were found to have less bioactivity when compared with Roy and DHR respectively. These results suggested that these nanoassemblies act as prodrugs for the release of cytotoxic lead molecules.
The second bioactive extract, P. mutabilis was subjected to a bio-guided fractionation of its acetone extract. From this extract, one new nor-abietane diterpene, (+)-(5S,10R)-10,11,12-trihydroxy-6,7-dioxo-20-nor-abieta-8,11,13-triene (1) alongside three known abietane-type diterpenoids Coleon-U-quinone (2), 8¿,9¿-epoxycoleon-U-quinone (3), and Coleon U (4) were isolated. The structure of the compounds was elucidated using different spectroscopic techniques (1D and 2D-NMR, LCMS, IR) and HRMS. From the ESI+ MS/MS fragmentation patterns analysis, an additional acetoxy derivative of an abietane diterpenoid, compound (5) was tentatively identified. Compounds 1-4 were quantified in the extract using HPLC-DAD. The isolated compounds were found to be unstable. Coleon U for instant was found to rapidly interchanges to its quinone derivative coleon U quinone. For this reason, a biosynthetic relation between the compounds was done. The results suggests that both the quinone (2) and the epoxyquinone (3) are formed directly from Coleon U (4). Cytotoxicity of the isolated compounds was done and their interaction with P-gp studied using the model systems human non-small cell lung carcinoma cells (NCI-H460), its MDR variant with P-gp expression (NCI-H460/R), and human embryonic pulmonary fibroblasts (MRC-5).
In conclusion, this work provides important information about the biological activity of several Plectranthus spp. In a review, and published works, we identified the importance of using Artemia salina as a screening model in natural product chemistry. The phytochemical study of P. mutabilis was done for the first time in this study and we identified compounds with a unique way of interacting with P-gp. In addition, we proposed two paths for the possible formation of epoxide 3 from 4. We equally successively prepared self-assembly nanoparticles of royleanones using oleic and squalene linkers these by improving the the aqueous solubility of 7¿-acetoxy-6ß-hydroxyroyleanone, 7¿-acetoxy-6ß-benzoyloxyroyleanone and 6,7-dehydroroyleanone.