Susan Billig

Furcellaria lumbricalis is an industrially important carrageenophyte. However, beyond the carrageenan characterization, the biochemical composition of this alga remains poorly understood. This study provides the first comprehensive description of the metabolome of F. lumbricalis and reveals pronounced biochemical heterogeneity in its thalli by examining the distribution of pigments, phenolic compounds, polysaccharides, and low-molecular-weight metabolites across apical, middle, and basal thallus zones. Understanding the intra-thallus biochemical profiles is necessary for the efficient use of algal feedstock. Untargeted GC-MS analysis of Furcellaria extracts revealed a high diversity of phenolic compounds, accounting for 27% of the annotated metabolome. Meristematic apical cells were enriched in organic acids of the TCA cycle, isofloridoside and various phenolic acids, such as caffeic, protocatechuic, and 3,4-dihydroxyphenylpyruvic, indicating active processes of respiration and secondary metabolism presumably conferring chemical defense. Mature cells of the middle zone accumulated carrageenans and heterosides, supporting structural investment and mobile carbon storage. The basal zone, apparently serving both resource storage and stress tolerance functions, featured a relatively high content of mono- and disaccharides, sugar alcohols, floridean starch, p-coumaric and 3-phenyllactic acids. Overall, these findings establish a metabolic framework for understanding the functional compartmentalization in red macroalgae and provide a foundation for future studies.

Brown algae are important primary producers in coastal ecosystems, where they provide habitat and food for numerous marine species. For humans, they provide raw materials (food, animal feed, and ingredients for pharmaceuticals and cosmetics) as well as ecosystem services such as coastal protection and carbon sequestration. The molecular characterization of brown algae is necessary to understand their role in ecosystems, their biochemical resources, and responses to environmental stresses—knowledge that is crucial for the sustainable use and biotechnological applications of seaweed. Within this context, we analyzed more than 300 primary and secondary metabolites by gas chromatography–mass spectrometry to elucidate the metabolic profiles of seven habitat-forming species of brown algae in the arctic and temperate seas. Metabolite profiles were discussed considering physiological and ecological characteristics of the different algae, thus revealing the taxon-specific biochemical signatures and metabolite patterns contributing to seaweed adaptation to their typical habitats. Three important groups of metabolites representing polyols, phenolic compounds, and organic acids, were analyzed and discussed in more detail. Our study revealed metabolic diversity of species from the same order and genus, thereby indicating a very distinct regulation at the molecular level to meet metabolic needs of the habitat. The knowledge of different compositions of algal extracts can be used to develop specialized applications for humans in cosmetic, medical, or nutritional sectors.

Background/Objectives: Propolis is a complex bee product with a composition that varies according to local vegetation, environmental conditions, and bee foraging behaviours. Recently, gas chromatography–mass spectrometry (GC–MS) has been employed in Uganda to analyse its volatile components. This study examined Ugandan propolis non-volatile metabolites to determine chemotypes and identify antibacterial compounds. Methods: Ethanolic extracts were analysed using liquid chromatography–high-resolution quadrupole time-of-flight mass spectrometry (LC-HR-QTOF-MS) in an untargeted MS/MS mode. Data processing was carried out using MZmine, then annotated with Global Natural Products Social Molecular Networking (GNPS) and SIRIUS. Chemometric methods assisted in identifying regional chemical signatures. Metabolites highlighted by the heatmap were evaluated for antibacterial activity using molecular docking against bacterial targets, followed by ADMET (absorption, distribution, metabolism, excretion, and toxicity) assessments. Results: Out of 3252 features, 234 and 52 putative compounds were annotated in GNPS and SIRIUS, respectively, as indicated by molecular networking, suggesting high chemical complexity. The chemical space mainly comprises flavonoids (including glycosides, aglycones, methylated, and prenylated derivatives), phenolic acids, amides, hydroxycinnamate derivatives, lignans, megastigmanes, and various diterpenoid skeletons. Multivariate analyses clearly distinguish geographical chemotypes, separating flavonoid-rich regions from diterpenoid-rich regions. Docking studies revealed flavonoids, diterpenoids, and lignans with strong predicted antibacterial activities and favourable ADMET profiles. Conclusions: This study provides the first LC–MS characterisation of the non-volatile metabolome of Ugandan propolis, thereby expanding its chemical diversity. Metabolomics and computational approaches lay a foundation for future ecological, chemotaxonomic, and pharmacological research.

Medicinal plants such as Centella asiatica , Conyza sumatrensis , and Justicia betonica are widely used in Uganda for traditional wound healing. However, the impact of cultivation conditions on their therapeutic potential remains poorly understood. This study compared the phytochemical profiles and bioactivities of hydroponically cultivated and wild‐collected material of these species from Lugazi Diocese, Uganda. Extracts were prepared using ethanol, methanol, and water, and analyzed by thin‐layer chromatography (TLC), high‐performance liquid chromatography (HPLC‐UV), headspace gas chromatography–mass spectrometry (HS‐GC–MS), and liquid chromatography–tandem mass spectrometry (LC–MS/MS). TLC and HPLC‐UV indicated terpenoids, flavonoids, and steroids, while HS‐GC–MS revealed predominantly monoterpenes and sesquiterpenes. LC–MS/MS annotated flavonoids, including quercetin‐3‐O‐glucuronoside, kaempferol‐3‐O‐rutinoside, and kaempferol, as well as triterpenoids such as asiatic acid and katononic acid. Antibacterial activity was evaluated against Bacillus subtilis , Escherichia coli , Pseudomonas fluorescens , and Saccharomyces cerevisiae using the agar well diffusion method. Anti‐inflammatory effects were assessed by IL‐6 and IL‐8 secretion, and cytotoxicity by MTT assay. Ethanol and methanol extracts exhibited moderate antibacterial activity, while aqueous extracts of wild C. asiatica and hydroponic C. sumatrensis significantly reduced IL‐6 secretion. No cytotoxic effects were detected. These findings suggest hydroponic cultivation preserves essential phytochemicals and bioactivities, supporting sustainable production of medicinal plants for therapeutic applications.

Propolis is a resinous substance collected by honeybees, and its long-known bioactivity urged research on its exact composition on active ingredients. It was suggested that chemical composition reflects the botanical sources and environmental conditions of its origin; however, information on differences related to geographical origin is still incomplete. Therefore, this study aimed to characterise the volatile and semi-volatile chemical constituents of Ugandan propolis from nine agro-ecological zones using headspace gas chromatography–mass spectrometry (HS-GC-MS) and derivatisation-based GC-MS, coupled with multivariate statistical analysis. In total, 213 volatile and 169 non-volatile compounds were tentatively identified, including monoterpenes (α-pinene), sesquiterpenes (α-copaene), triterpenoids (β-amyrin acetate), diterpene resin acids (abietic acid), phenolic acids (caffeic acid), alkylresorcinols (bilobol) and many others. Multivariate chemometric modelling using partial least-squares discriminant analysis (PLS-DA), orthogonal PLS-DA (oPLS-DA) showed strong geographic discrimination of samples (Q² > 0.90) for several district comparisons. Heatmap clustering and variable importance in projection (VIP) analysis identified chemical markers. Notably, oPLS-DA revealed excellent discrimination between Nakasongola and Bushenyi, and between Adjumani and Bushenyi, in both volatile and non-volatile datasets. The findings provide the first comprehensive chemical profiling of Ugandan propolis, demonstrating the utility of combined GC-MS approaches and multivariate analysis for regional differentiation. This work lays the groundwork for standardising propolis preparations and establishing appropriate quality control in pharmacological applications.

Conyza sumatrensis is a plant of the Asteraceae family widespread in the tropical and subtropical regions of all continents. The plant is applied in folk medicine to treat malaria and helminth infections as well as other diseases. In Uganda, for example, the plant is traditionally used against ectoparasites and for wound healing. In this work, we describe a comprehensive analytical approach to investigate the metabolic profile of C. sumatrensis supported by database-assisted annotation and in silico techniques. The study aimed to analyze the metabolic profile of C. sumatrensis using multiple analytical techniques due to the complexity of the plant composition. Therefore, we employed a combination of thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). From the GC-MS experiments, more than 40 compounds could be annotated that had not been found in C. sumatrensis before. A number of these substances are known to possess relevant bioactivities, including antibacterial properties. Indeed, ethanolic extracts demonstrated antimicrobial activity against representative strains of both Gram-positive and Gram-negative bacteria, as shown by agar diffusion and microdilution assays. Using LC-MS/MS data, a feature-based molecular network was constructed to facilitate the comparison of two extraction solvents: water and ethanol. The majority of the features were detected in both of the extracts. However, some features were only detected using one of the extraction solvents. Our work provided valuable insights into the chemical profile of C. sumatrensis and lays the foundation for future research into its medicinal properties.

Succinate is a pivotal tricarboxylic acid cycle metabolite but also specifically activates the G_i‐ and G_q‐coupled succinate receptor 1 (SUCNR1). Contradictory roles of succinate and succinate‐SUCNR1 signaling include reports about its anti‐ or pro‐inflammatory effects. The link between cellular metabolism and localization‐dependent SUCNR1 signaling qualifies as a potential cause for the reported conflicts. To systematically address this connection, we used a diverse set of methods, including several bioluminescence resonance energy transfer‐based biosensors, dynamic mass redistribution measurements, second messenger and kinase phosphorylation assays, calcium imaging, and metabolic analyses. Different cellular metabolic states were mimicked using glucose (Glc) or glutamine (Gln) as available energy substrates to provoke differential endogenous succinate (SUC) production. We show that SUCNR1 signaling, localization, and metabolism are mutually dependent, with SUCNR1 showing distinct spatial and energy substrate‐dependent G_i and G_q protein activation. We found that Gln‐consumption associated with a higher rate of oxidative phosphorylation causes increased extracellular SUC concentrations, accompanied by a higher rate of SUCNR1 internalization, reduced miniG_q protein recruitment to the plasma membrane, and lower Ca²⁺ signals. In Glc, under basal conditions, SUCNR1 causes stronger G_q than G_i protein activation, while the opposite is true upon stimulation with an agonist. In addition, SUCNR1 specifically interacts with miniG proteins in endosomal compartments. In THP‐1 cells, polarized to M2‐like macrophages, endogenous SUCNR1‐mediated G_i signaling stimulates glycolysis, while G_q signaling inhibits the glycolytic rate. Our results suggest that the metabolic context determines spatially dependent SUCNR1 signaling, which in turn modulates cellular energy homeostasis and mediates adaptations to changes in SUC concentrations.

The brown alga Pelvetia canaliculata is one of the species successfully adapted to intertidal conditions. Inhabiting the high intertidal zone, Pelvetia spends most of its life exposed to air, where it is subjected to desiccation, light, and temperature stresses. However, the physiological and biochemical mechanisms allowing this alga to tolerate such extreme conditions are still largely unknown. The objective of our study is to compare the biochemical composition of Pelvetia during the different phases of the tidal cycle. To our knowledge, this study is the first attempt to draft a detailed biochemical network underneath the complex physiological processes, conferring the successful survival of this organism in the harsh conditions of the high intertidal zone of the polar seas. We considered the tide-induced changes in relative water content, stress markers, titratable acidity, pigment, and phlorotannin content, as well as the low molecular weight metabolite profiles (GC-MS-based approach) in Pelvetia thalli. Thallus desiccation was not accompanied by considerable increase in reactive oxygen species content. Metabolic adjustment of P. canaliculata to emersion included accumulation of soluble carbohydrates, various phenolic compounds, including intracellular phlorotannins, and fatty acids. Changes in titratable acidity accompanied by the oscillations of citric acid content imply that some processes related to the crassulacean acid metabolism (CAM) may be involved in Pelvetia adaptation to the tidal cycle.