Substances of natural and synthetic origin were studied using analytical, bioassay guided isolation, metabolomics and medicinal chemistry techniques. In a section focused on the plant family Marcgraviaceae, a validated method for the quantification of six pentacyclic triterpenes (α and β Amyrin lupeol, ursolic acid, betulin and betulinic acid) in the Souroubea spp was developed. Quantification of the triterpenes in the crude extracts was achieved using HPLC-APCI mass selective detection. The calibration curves for the five triterpenes evaluated were highly linear (r2 >0.993) and percentage recovery from spiked samples were greater than 94% for all compounds. The LOD for betulinic acid was 0.01 µg for betulinic acid on column and LOQ was 0.03 µg. The method was successfully applied to 41 crude extracts from leaf and stem of Souroubea spp, from two locations in Costa Rica. The method is suitable for quality control of raw materials used in the manufacture of natural health products. The use of modern metabolomic techniques, UHPLC-QTOF allowed the identification of five putative makers that can potentially be used in distinguishing between the two Souroubea species.
The validated method was used in the quantification of the above triterpenes in a total of thirteen Marcgraviaceae species collected in Costa Rica. It was established that betulinic acid and β- Amyrin could be used as makers for this family of tropical vines. These same thirteen plants extracts were evaluated in antifungal and quorum sensing inhibition bioassays. Marcgravia nervosa was the only species that showed significant activity in both bioassays. Bioassay guided fractionation of the crude ethanolic extract of M. nervosa led to the identification of 2-methoxynaphthoquinone as the bioactive compound responsible for the bioactivity. The crude leaf ethanolic extract from M. nervosa showed a significant inhibition of QS comparable or somewhat better than D. pulchra extracts with the M. nervosa extract showing stronger inhibiting QS with a halo of 21.8mm, more than D. pulcra extracts which generated a halo of 15.9mm. The active quinone has a MIC of 85 µM against Saccharomyces cerevisiaBY4741 (haploid) and 100 µM against Saccharomyces cerevisiae BY4743 (diploid) compared to berberine (positive control) with a MIC 600 µM for both strains. This quinone is not present in any of the other twelve species of Marcgraviaceae available to us.
In work focusing on organic synthesis, a total of 57 semi-synthetic derivatives of dillapiol, safrol and piperonal were prepared and evaluated for their inhibitory activity in a CYP 3A4 bioassay to assess their potential use as pesticide synergists. The synergistic activity of dillapiol has been improved 45 fold; analog 31 has an IC50 = 0.2 µM compared with dillapiol IC50= 9.18 µM. A number of other compounds structurally related to 31 showed similar levels of activity.
A screening of a compound library identified the amino sulfoxide 3 as a potential lead for the design of a selective connexin blocker with potential application in the treatment of spinal cord injuries. The use of X-ray crystallography permitted the correction of the original structure assigned to 3. Once the structure was corrected a total of 6 analogs were prepared. Compound 3 has the highest inhibition of GJIC whereas compound 8 and compound 2, reduced anionic hemi-channel activity. Compound 2 also reduced the cationic activity of the hemi-channels.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OOU.#10393/30315 |
| Date | 10 December 2013 |
| Creators | Carballo Arce, Ana F. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thèse / Thesis |
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