Metabolomic exploration of pharmacologically relevant metabolites in Moringa oleifera and Moringa ovalifolia through the use of UPLC-qTOF-MS and multivariate models
Makita, Charlene Sampu
Plant metabolomics is considered a holistic qualitative and quantitative analysis of primary and secondary metabolites under specific conditions. Metabolomics provides functional information that is important in the biological studies of plants. Moreover, chromatographic techniques in combination with mass spectrometry are presently commonly utilized analytical technologies that are used in metabolomics studies. Moringa oleifera (M. oleifera) is an acclaimed medicinal herb and is considered one of the most superior plants based on its nutritional and medicinal attributes. Signature compounds such as chlorogenic acids and flavonoids found in Moringa plants are considered beneficial as they are responsible for the health properties found in these plants. Out of the 13 species belonging to the Moringaceae family, M. oleifera is the most widely studied. Furthermore, plants are known to produce compounds, such as flavonoids, as a response to biotic stresses (pest resistance) and abiotic stresses (harsh environmental conditions such as drought or cold). Other species belonging to the Moringaceae family such as Moringa ovalifolia (M. ovalifolia), located in the dry desert and semi-desert areas of Namibia, has not been reported much in literature. Moreover, there is very little work done on other classes of compounds that are possibly present in M. ovalifolia. Therefore, the significant correlation between desert plants and their possible increased flavonoid content is of interest in this study and is worth investigating. Moreover, in an effort to compare Moringa species in that regard, a holistic approach to metabolite fingerprinting using UPLC-qTOF-MS was thus employed for the characterization of possible metabolite markers and taxonomical differences in M. ovalifolia and M. oleifera plant species (Paper I). From the results, 17 flavonoid compounds were identified. Interestingly, M. oleifera and M. ovalifolia had a similar aglycone profile, however, they had a different sugar moiety. Rutinoside sugar moieties were only found to be present in M. ovalifolia indicating that it is only capable of attaching the rutinoside sugar moiety to its flavonoid skeleton. M. oleifera, however, is capable of attaching many sugar moieties to its flavonoid skeleton. The outcomes of this research additionally demonstrated for the first time the significance of sugar attachment for taxonomical classification of related species and that the contrasts between the grouped species are likely because of genetic variations as opposed to environmental influences. This study further provided potential chemotaxonomic biomarkers and a classification model was generated to classify and differentiate between closely related Moringa species utilizing multivariate analysis (Paper III). Moreover, chlorogenic acids which are esters formed between derivatives such as cinnamic acid and quinic acid molecules, were identified in M. ovalifolia plants species for the first time (Paper II ). Chlorogenic acids are difficult to identify and differentiate since they are structurally complex. This study demonstrated the effectiveness of an UPLC-ISCID-MS/MS based platform to aid in the profiling of isomers and derivatives of chlorogenic acids present in M. ovalifolia. This approach further showed M. ovalifolia as a valuable source of molecules with therapeutic potential. Based on the classification model generated in Paper II, the biomarkers identified were utilized in order to differentiate between 12 M. oleifera cultivars (Paper III). Three sought after flavonoid compounds, namely, quercetin rutinoside (rutin), kaempferol rutinoside and isorhamnetin rutinoside were identified as potential chemotaxonomic markers amongst the 12 Moringa cultivars. Metabolite distribution patterns of the 12 cultivars were analyzed using a metabolomics approach with the aid of UHPLC-qTOF-MS in combination with multivariate data models such as principal component analysis (PCA), hierarchical clustering analysis (HCA) and box-whiskers plot. According to the results, three main cultivars, namely: TOT4977, CHM and TOT5330 were identified as potential cultivars for pharmacological and nutritional purposes according to the presence and abundance of the three studied rutinoside bearing flavonoid molecules.
A thesis submitted to the Faculty of Science University of the Witwatersrand. Johannesburg, 2017.
Makita, Charlene Sampu (2017) Metabolomic exploration of pharmacological relevant metabolites in Moringa oleifera and Moringa ovalifolia through the use of UPLC-qTOF-MS and multivariate models, University of the Witwatersrand, Johannesburg, <http://hdl.handle.net/10539/23492>