Madala, N. E.Mathomu, L. M.Moyo, N. B.Sekgobela, Rose Mailane2026-06-242026-06-242026-05-19Sekgobela, R.M. 2026. Mass spectrometric and chemometric characterisation of photo-induced isomerisation of hydroxycinnamic acid derivatives from Viscum combreticola. . .https://univendspace.univen.ac.za/handle/11602/3301M.Sc. in BiochemistryDepartment of Biochemistry and MircobiologyExposure of hydroxycinnamic acid (HCA)-containing compounds to excessive sunlight induces geometrical isomerisation, enabling plants to mitigate photo-oxidative stress through enhanced metabolic plasticity. With the increasing intensity of solar radiation associated with climate change, such light-induced transformations can further amplify the complexity of plant metabolome, and this poses analytical challenges, particularly in distinguishing and resolving closely related isomers. In this study, ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-qTOF-MS) was employed to characterise HCA-containing compounds in methanolic extracts of Viscum combreticola treated with UV irradiation. Data was analysed using multivariate statistical tools, molecular networking and density functional theory (DFT) was used to rationalise some mass spectrometric processes. A sodium adduct of dimeric 4-cis-caffeoylquinic acid (4-cis-CQA) at m/z 729.164 characterised for the first time was shown to be formed from interactions between neutral and doubly deprotonated 4-cis-CQA molecules, with a Na⁺ ion stabilised between their functional groups. The formation of the (Na-cis-CQA) adduct is believed to have yet to be investigated for its biological consequences. Principal component analysis (PCA) and biplots captured dynamic transformations in HCA-containing metabolites following UV treatment, highlighting their potential in visualising metabolomic shifts driven by environmental stressors. Furthermore, triple quadrupole (QqQ) mass spectrometry was successfully applied to differentiate between UV-treated and non-treated samples, followed by data analysis using principal component analysis, hierarchical clustering analysis, and volcano plots, demonstrating its potential for sample authentication where the chemistry of the sample is already known. Overall, this study showed that UV treatment promotes metabolite diversity, reflecting the metabolic plasticity of HCA derivatives. It also emphasised that chemical transformations such as alkali metal adduct formation can enhance isomer differentiation, complementing robust chromatographic separation. Therefore, advancing data visualisation in understanding plant metabolic responses to environmental stress. Future studies should investigate the biological activities of cis isomers of HCA derivatives as they may hold potential pharmacological potential.enUniversity of VendaViscum combreticolaUCTDHydroxycinnamic acidsUv irradiationGeometrical isomersMass spectrometryMultivariate statisticsMolecular networkingDissertationSekgobela RM. Mass spectrometric and chemometric characterisation of photo-induced isomerisation of hydroxycinnamic acid derivatives from Viscum combreticola. []. , 2026 [cited yyyy month dd]. Available from:Sekgobela, R. M. (2026). <i>Mass spectrometric and chemometric characterisation of photo-induced isomerisation of hydroxycinnamic acid derivatives from Viscum combreticola</i>. (). . Retrieved fromSekgobela, Rose Mailane. <i>"Mass spectrometric and chemometric characterisation of photo-induced isomerisation of hydroxycinnamic acid derivatives from Viscum combreticola."</i> ., , 2026.TY - Thesis AU - Sekgobela, Rose Mailane AB - Exposure of hydroxycinnamic acid (HCA)-containing compounds to excessive sunlight induces geometrical isomerisation, enabling plants to mitigate photo-oxidative stress through enhanced metabolic plasticity. With the increasing intensity of solar radiation associated with climate change, such light-induced transformations can further amplify the complexity of plant metabolome, and this poses analytical challenges, particularly in distinguishing and resolving closely related isomers. In this study, ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-qTOF-MS) was employed to characterise HCA-containing compounds in methanolic extracts of Viscum combreticola treated with UV irradiation. Data was analysed using multivariate statistical tools, molecular networking and density functional theory (DFT) was used to rationalise some mass spectrometric processes. A sodium adduct of dimeric 4-cis-caffeoylquinic acid (4-cis-CQA) at m/z 729.164 characterised for the first time was shown to be formed from interactions between neutral and doubly deprotonated 4-cis-CQA molecules, with a Na⁺ ion stabilised between their functional groups. The formation of the (Na-cis-CQA) adduct is believed to have yet to be investigated for its biological consequences. Principal component analysis (PCA) and biplots captured dynamic transformations in HCA-containing metabolites following UV treatment, highlighting their potential in visualising metabolomic shifts driven by environmental stressors. Furthermore, triple quadrupole (QqQ) mass spectrometry was successfully applied to differentiate between UV-treated and non-treated samples, followed by data analysis using principal component analysis, hierarchical clustering analysis, and volcano plots, demonstrating its potential for sample authentication where the chemistry of the sample is already known. Overall, this study showed that UV treatment promotes metabolite diversity, reflecting the metabolic plasticity of HCA derivatives. It also emphasised that chemical transformations such as alkali metal adduct formation can enhance isomer differentiation, complementing robust chromatographic separation. Therefore, advancing data visualisation in understanding plant metabolic responses to environmental stress. Future studies should investigate the biological activities of cis isomers of HCA derivatives as they may hold potential pharmacological potential. DA - 2026-05-19 DB - ResearchSpace DP - Univen KW - Viscum combreticola KW - Hydroxycinnamic acids KW - Uv irradiation KW - Geometrical isomers KW - Mass spectrometry KW - Multivariate statistics KW - Molecular networking LK - https://univendspace.univen.ac.za PY - 2026 T1 - Mass spectrometric and chemometric characterisation of photo-induced isomerisation of hydroxycinnamic acid derivatives from Viscum combreticola TI - Mass spectrometric and chemometric characterisation of photo-induced isomerisation of hydroxycinnamic acid derivatives from Viscum combreticola UR - ER -