: A number of papers reporting antimicrobial properties of extracts, essential oils, resins and various classes of compounds isolated from higher plants have been published in recent years; however, a comprehensive analysis of plant-derived antimicrobial agents currently applied in practice for the improvement of human health is still lacking. This review summarizes data on clinical efficacy, antimicrobial effects and the chemistry of commercially available antibacterial and antifungal agents of plant origin currently used in the prevention and treatment of gastrointestinal, oral, respiratory, skin, and urinary infections. As a result of an analysis of the literature, more than 40 plant-derived over-the-counter pharmaceuticals, dietary supplements, cosmetics, herbal medicines, and functional foods containing complex mixtures (e.g. Glycyrrhiza glabra extract, Melaleuca alternifolia essential oil, and Pistacia lentiscus resin), pure compounds (e.g. benzoic acid, berberine, eucalyptol, salicylic acid and thymol) as well as their derivatives and complexes (e.g. bismuth subsalicylate and zinc pyrithione) have been identified. The effectiveness of many of these products is illustrated by results of clinical trials and supported by data on there in vitro antimicrobial activity. A broad spectrum of various commercial products currently available on the market and their welldocumented clinical efficacy suggests that plants are prospective sources for the identification of new types of antimicrobial agents in future. Innovative approaches and methodologies for effective proof-of-concept research and the development of new types of plant-derived products effective against recently emerging problems related to human microbial diseases (e.g. antimicrobial resistance) are also proposed in this review.

In this study we examined the in vitro synergistic effect of baicalin, the flavone constituent of Scutellaria spp., in combinations with oxytetracycline and tetracycline on the growth of Staphylococcus aureus. The MICs were determined by the broth microdilution method and the effect of combinations was evaluated according to the sum of fractional inhibitory concentration indices (FICIs). Synergistic activity (FICI ≤ 0.5) was observed for combinations of baicalin with oxytetracycline or tetracycline against 4 of 10 strains tested, whereas the baicalin/oxytetracycline combination possessed the strongest synergistic effect (FICI = 0.418). Baicalin acts synergistically with oxytetracycline and tetracycline, enhancing its antimicrobial activity against S. aureus, including methicillin- and tetracycline-resistant strains.

Garcinia kola Heckel (Clusiaceae), known as bitter kola, is a multipurpose tree indigenous to West and Central Africa. This highly preferred species is called “wonder plant” because all of its parts can be used as medicine. Its seeds, the most valued product of the tree, are commonly eaten to prevent/cure gastric disorders and for their typical astringent taste. There is a vast evidence that bioactive components of the seeds can serve as alternative medicine to treat/prevent severe illnesses such as malaria, hepatitis and immune-destructive diseases. Despite the species’ pharmaceutical potential and its high preference by West and Central African communities, G. kola is still at the beginning of its domestication process. Even though, there are numerous scientific articles published on species‘ biological activities, it is a difficult task to find basic information on its diversity, distribution, genetics, silvicultural management or botany. Therefore, in this very first review published on G. kola, we summarize all relevant information known about the species, target some of the challenges connected with its cultivation and propose a leading direction for future research and domestication process.

Essential oils (EOs) from Indian spices like Elettaria cardamomum (L.) Maton (small green cardamom), Syzygium aromaticum (L.) Merr. & L.M. Perry (clove), Cinnamomum zeylanicum Blume (cinnamon quills), and Cinnamomum tamala (Buch.-Ham.) T. Nees & C. H. Eberm (Indian bay leaves) exhibit a broad spectrum range of biological activity including antibacterial and antifungal activity. Yet, there is a lack of data regarding the antimicrobial activity of their formulations. Also, the link between the antimicrobial effect of individual EO with their chemical composition and molecular interaction with bacterial pathogens has not been systematically explored. Therefore, the objectives of the current study were to evaluate the antimicrobial activity and phytochemical characterization of EOs and to bridge the gap between them through in-silico molecular interactions. The antibacterial activity of EOs of four different spices and their formulations against foodborne pathogens such as Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa was evaluated using the disc volatilization method. The chemical profile of the individual EO was determined through GC-MS analysis and molecular interactions of identified major components with bacterial proteins were carried out through molecular docking studies. All EOs and their formulations exhibited antibacterial activity ranging from 5.92 to 24.55 mm and 11–23.52 mm, respectively. Among all EOs, cinnamon and formulation C (cardamom: cinnamon- 2:1) exhibited the highest antibacterial activity. The composition of the EOs included sesquiterpenes, monoterpenoids, monoterpenes, and, phenylpropanoids such as (E)-cinnamaldehyde, δ-cadinene, α-copaene, eugenol, caryophyllene, eugenol acetate, methyl eugenol, menthadiene, eucalyptol, α-terpinyl acetate, and sabinene. Furthermore, docking study revealed that the abundant compounds from cinnamon EO mainly α-copaene and δ-cadinene had a high binding affinity towards the bacterial essential proteins which increases the bacterial susceptibility towards cinnamon EO. The selected EOs and their formulations were systematically analysed and they were effective against foodborne pathogens. The current findings suggest the application of these EOs against food pathogens with further research.

Smallanthus sonchifolius (yacon) is an edible tuberous Andean shrub that has been included in the diet of indigenous people since before recorded history. The nutraceutical and medicinal properties of yacon are widely recognized, especially for the improvement of hyperglycemic disorders. However, the chemical diversity of the main bioactive series of caffeic acid esters has not been explored in detail. In this metabolomics study, we applied the latest tools to facilitate the targeted isolation of new caffeic acid esters. Using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), we analyzed extracts from different organs (roots, vascular tissues of the stems, stem epidermis, leaves, bracts, and ray flowers) and followed a feature-based molecular networking approach to characterize the structural diversity of caffeic acid esters and recognize new compounds. The analysis identified three potentially new metabolites, one of them confirmed by isolation and full spectroscopic/spectrometric assignment using nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), and MS/MS. This metabolite (5-O-caffeoyl-2,7-anhydro-d-glycero-β-d-galacto-oct-2-ulopyranosonic acid), along with eight known caffeic acid esters, was isolated from the roots and stems. Furthermore, based on detailed tandem MS analyses, we suggest that the two isomeric monocaffeoyl-2,7-anhydro-2-octulopyranosonic acids found in yacon can be reliably distinguished based on their characteristic MS² and MS³ spectra. The outcome of the current study confirms the utility of feature-based molecular networking as a tool for targeted isolation of previously undescribed metabolites and reveals the full diversity of potentially bioactive metabolites from S. sonchifolius.