Deciphering the chemistry of host-parasitic plants interactions using the UHPLC-q-TOF-MS and chemometrics

While mistletoes in the genus Viscum are extensively used in ethnomedicine globally, the parasitic nature of these plants can impact their secondary metabolite composition and thereby, influence their medicinal properties. The main objective of this study was to contrast the metabolome of Viscum combreticola Engl. (African mistletoe) collected from two distinct host plants, namely, Combretum erythrophyllum and Pseudolachnostylis maprouneifolia Pax. Utilizing ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry and classical molecular networking, it was observed that the metabolic profiles of V. combreticola samples from these two host plants exhibited significant similarities. However, the metabolic profile of V. combreticola was notably distinct from that of these two hosts thereby, highlighting the independence of the chemistry of the mistletoe from its host plants. This study further explored the chemical composition of this understudied plant comprehensively, revealing that V. combreticola is predominantly composed of chemically diverse hydroxycinnamic acid derivatives. Interestingly, the methanolic crude extracts of this plant were found to contain cis isomers of chlorogenic acids (CGAs) and this was confirmed through in vitro UV irradiation of the plant extracts. The presence of cis isomers observed in V. combreticola suggests a form of adaptive plasticity launched by these plants in response to photo-oxidative stress since they get exposed to excessive sunlight on the canopy of their host plants, especially in tropical regions. Moreover, the diverse CGA composition of these plants could be an approach they use to maximise their defensive mechanism against excessive sunlight exposure through the “better be safe than sorry” strategy. V. combreticola was also found to contain rare flavonoids, viscutins, that were characterized for the first time in this study by their unique spectral fingerprints resulting from the retro Diels Alder reaction using a molecular networking complementary tool, tandem MS latent Dirichlet allocation (MS2LDA). As a result, this highlights the great potential of this tool in uncovering complex gas phase reactions that occur in mass spectrometers and future studies should take advantage of the unique attributes of this tool in revealing hidden spectral features from MS/MS data sets. Moreover, inspired by the pharmacological importance of V. album (European mistletoe), its phytochemical composition was compared to that of V. combreticola using the UHPLC-q-TOF-MS and classical molecular networking. These two species were found to be chemotaxonomically distinct, with V. album mainly consisting of flavonoids conjugated to 3-hydroxy-3-methylglutaric acid. Lastly, chemically diverse polyphenols including flavonoids and diacylated CGAs identified in V. combreticola were found to be potential therapeutic agents for target proteins associated with the pathogenesis of type 2 diabetes mellitus using network pharmacology. Therefore, revealing the potential of the constituents of this plant in managing this complex disease. However, further studies are needed to fully understand the therapeutic potential of these compounds derived from V. combreticola. Overall, this study provided valuable insights into the complex chemical relationship between mistletoes and their hosts using mass spectrometry and molecular networking while highlighting identified novel compounds in V. combreticola with promising therapeutic attributes.

Author dc:creator

• Moyo, Nakisani Barbara

Advisors dc:contributor.advisor

• Madala, N. E.
• Tavengwa, N. T.

Statement dc:rights

• University of Venda

Language dc:language.iso

en

Repository record dc:identifier.uri

http://univendspace.univen.ac.za/handle/123456789/2704

OAI identifier oai:identifier

oai:univendspace.univen.ac.za:123456789/2704