LC-MS Based Metabolite Fingerprinting of Coccinia Plants Reveals Glycoisomerization as a Structual Diversification Strategy in Flavanoid Chemical Space

A Relook into the Flavonoid Chemical Space of Moringa oleifera Lam. Leaves through a Combination of LC-MS and Molecular Networking

Moringa oleifera Lam. is a functional tree that is known to produce a variety of metabolites with purported pharmacological activities. It is frequently called the "miracle tree" due to its utilization in numerous nutraceutical and pharmacological contexts. This study was aimed at studying the chemical space of M. oleifera leaf extracts through molecular networking (MN), a tool that identifies metabolites by classifying them based on their MS-based fragmentation pattern similarities and signals. In this case, a special emphasis was placed on the flavonoid composition. The MN unraveled different molecular families such as flavonoids, carboxylic acids and derivatives, lignin glycosides, fatty acyls, and macrolactams that are found within the plant. In silico annotation tools such as network annotation propagation (NAP) and DEREPLICATOR, an unsupervised substructure identification tool (MS2LDA), and MolNet enhancer were also explored to further compliment the classic molecular networking output within the Global Natural Product Social (GNPS) site. In this study, common flavonoids found within Moringa oleifera were further annotated using MS2LDA. Utilizing computational tools allowed for the discovery of a wide range of structurally diverse flavonoid molecules within M. oleifera leaf extracts. The expansion of the flavonoid chemical repertoire in this plant arises from intricate glycosylation modifications, leading to the creation of structural isomers that manifest as isobaric ions during mass spectrometry (MS) analyses.

Diverse chemical modifications of the chlorogenic acid composition of Viscum combreticola Engl.: A premise for the state of readiness against excessive sunlight exposure

Mistletoe plants that are positioned on the canopy of their hosts are more susceptible to UV radiation exposure. These aerial plants are resistant to damage by UV radiation due the presence of epidermal constituents such as the cuticle, cork layer, trichomes and antioxidant secondary metabolites. In response to the photo-oxidative stress associated with UV exposure, plants generally deploy photo-protective responsive mechanisms that involve the biosynthesis of UV absorbing phenolic compounds such as chlorogenic acids (CGAs). The hydroxycinnamic acid moieties of these CGAs are predominantly in the trans configuration, naturally. However, excessive sunlight exposure of plants containing these compounds can result in geometrical isomerisation, characterized by the formation of cis isomers. Therefore, in this study, the effect of UV light radiation on the CGA composition of Viscum combreticola Engl. (Santalacaeae) plants using an in vitro model was unravelled through UHPLC-q-TOF-MS-based metabolic profiling. Interestingly, the findings of this study revealed that this plant has a diverse chemical composition of CGAs that is characterized by epimerization, monoacylation, homodiacylation and heterodiacylation of the quinic acid (QA), thereby, contributing to the state of readiness in these plants against sunlight or UV exposure. In addition to the commonly reported cinnamoyl containing heterodiacylated CGAs, hydroxybenzoyl containing heterodiacylated CGAs were also reported in this study. Moreover, cis isomers (24 in total) of some CGAs were identified in the non-irradiated samples and the formation of these compounds has been reported to help plants in the mitigation of photo-oxidative stress. An additional 28 cis isomers of CGAs and HCA derivatives were observed in the UV-irradiated samples, hence, further increasing the complexity of the metabolome of this plant, with a total of 108 compounds identified in this study. The presence of epimers, positional and geometrical isomers of these compounds could be a biochemical strategy to maximize the chemical arsenal of this plant to withstand the photo-oxidative stress posed by UV radiation from the sunlight. Due to purported pharmacological properties associated with the identified compounds these parasitic plants can be a rich source of prospective therapeutic compounds that can be employed as drug discovery leads. Moreover, UV radiation might be essential in future to produce potent drugs since plants naturally produce these compounds in low quantities.

Metabolomics and Molecular Networking to Characterize the Chemical Space of Four Momordica Plant Species

Momordica plant species (Cucurbitaceae), have been used for centuries in traditional medicine and for nutritional purposes. Plants from this family are thus claimed to be phytochemically rich, representing an inexhaustible source of natural products. However, the chemical space of these Momordica species has not yet been fully decoded, and due to the inherent complexity of plant metabolomes, the characterization of the Momordica phytochemistry remains challenging. Thus, in this study we propose the use of molecular networking to unravel the molecular families within the metabolomes of four Momordica species (M. cardiospermoides, M. balsamina, M. charantia and M. foetida) and highlight the relevance of molecular networking in exploring the chemotaxonomy of these plants. In silico annotation tools (Network Annotation Propagation and DEREPLICATOR) and an unsupervised substructure identification tool (MS2LDA) were also explored to complement the classical molecular networking output and integration using MolNetEnhancer within GNPS. This allowed for the visualisation of chemical classes and the variety of substructures within the molecular families. The use of computational tools in this study highlighted various classes of metabolites, such as a wide range of flavonoids, terpenoids and lipids. Herein, these species are revealed to be phytochemically rich plants consisting of many biologically active metabolites differentially distributed within the different species, with the metabolome of M. cardiospermoides dereplicated in this paper for the first time.