Isolation of triterpenes from propolis (bee glue)

Propolis (bee glue) is a natural substance produced by bees upon collection of mainly plant resins. Bees use it as antiseptic sealing agent between honeycombs and to preserve the hive from external contamination. Numerous scientific studies have been published on the biological properties of propolis including its anti-inflammatory, anti-oxidant, immunostimulant, antitumour and antimicrobial activity. Different propolis chemotypes have been characterised based on the nature of the plant-derived substances present and the geographical origin of collection. Here, we describe the isolation of nine triterpenes from a sample of propolis originating from North-Western Cameroon. All compounds were identified following analysis of their spectroscopic data and comparison with previously published reports

Plant-derived chemicals : a source of inspiration for new drugs

Plants have a long history of use as traditional remedies to treat a range of diseases and the diverse chemicals that they produce have provided great inspiration for the design of new drugs to date. Many plants have yet to be investigated for the presence of biologically-active products. This Special Issue presents a collection of scientific studies which report on the medicinal potential of plants. It also highlights the importance of preserving ethnobotanical knowledge and plant biodiversity worldwide to sustain future drug discovery from plant sources

A strong inhibitory effect of heather honey, propolis and medicinal plant extracts on biofilm formation by pathogenic bacteria

Introduction: P. aeruginosa and S. aureus are opportunistic pathogens that cause a wide range of infections. Their increasing resistance to antibiotics is a serious concern and making them susceptible to treatments is now more essential than ever. There is a need to discover new biofilm inhibitors to increase the susceptibility of these bacteria to antibiotics. Hypothesis and aims: To evaluate the antibiofilm activity of heather honey, propolis and medicinal plant extracts against P. aeruginosa and S. aureus. Methodology: Determination of optimum biofilm growth was carried out using a time-course assay over 24 h intervals, using P. aeruginosa PA14 and S. aureus NCTC 4135 strains. The inhibitory effects of all extracts were determined by biofilm inhibition assay in 24-well plates, with biofilms stained with crystal violet and de-stained with ethanol:acetone; OD were measured at 550 nm. Planktonic growth was measured at 600 nm and samples from the wells were streaked to determine bactericidal effects. Results: Heather honey extracts inhibited both P. aeruginosa and S. aureus by 68%. At 60 μg/mL, one of the propolis extracts promoted biofilm growth of both pathogens. Two other propolis extracts also promoted growth in P. aeruginosa but inhibited biofilm formation in S. aureus by 76.5% and 13.8%, respectively. Three plant extracts inhibited S. aureus biofilm by 7.5%, 10.2% and 87.6% and inhibited P. aeruginosa by −34.9%, 34.7% and 19.4%, respectively. Conclusion: All samples showed varying biofilm inhibition capabilities, but biofilm formation seemed to be more easily inhibited in S. aureus than in P. aeruginosa

Chemical diversity and biological activity of African propolis

Natural remedies have for centuries played a significant role in traditional medicine and continue to be a unique reservoir of new chemical entities in drug discovery and development research. Propolis is a natural substance, collected by bees mainly from plant resins, which has a long history of use as a folk remedy to treat a variety of ailments. The highly variable phytochemical composition of propolis is attributed to differences in plant diversity within the geographic regions from which it is collected. Despite the fact that the last five decades has seen significant advancements in the understanding of the chemistry and biological activity of propolis, a search of the literature has revealed that studies on African propolis to date are rather limited. The aim of this contribution is to report on the current body of knowledge of African propolis, with a particular emphasis on its chemistry and biological activity. As Africa is a continent with a rich flora and a vast diversity of ecosystems, there is a wide range of propolis phytochemicals that may be exploited in the development of new drug scaffolds

Natural antibiofilm agents and the need for antibiofilm drug leads

Plant with medicinal property contains different types of bioactive compounds and these compounds are effective against certain diseases. Biofilm infection is a disease caused by biofilm which is associated with the respiratory and gastrointestinal infections. Biofilm-producing bacteria as such Pseudomonas aeruginosa strain PA14 is a serious treat in hospitals. The bacterium possesses many virulent factors that contributed to its pathogenesis and resistance thus caused the inhibition and removal of its biofilms a difficult task. This study therefore attempts to identify natural antibiofilm agents against the P. aeruginosa PA14 biofilms. The activity of plant extracts and subsequently purified compounds was evaluated using a stepwise separation process called bioassay-guided fractionation. The fractionation process involved the use of chromatographic techniques and compounds were identified using NMR, GC-MS and LC-MS. A total of four bioactive fractions namely (E333F1S1), (E341), (HA6) and (M338B) have been discovered with antibiofilm activity and were selected for further investigation. The active fraction from Ribes nigrum leaf (E333F1S1) contained mixtures of alkanes while active extract of Sambucus nigra flower (E341) contained a mixture of ursolic acid and oleanolic acid. The LC-MS analysis on Coriandrum sativum seeds (HA6) revealed the presence mixture of oxygenated monoterpenes, while another active fraction of C. sativum seeds (M338B) showed the presence of carboxylic acid, carboxylate, tetraone, glycerol, carbohydrate and fatty acids. Thus, the discovery of potential bioactive compounds from this study could be further investigated as antibiofilm drug leads to battle the infections by P. aeruginosa PA14 biofilm in the near future

Editorial : metal-complexed molecules of natural and synthetic origin: pharmacological advances and therapeutic applications

In recent years, there has been a growing interest in metal-based (particularly coordination) compounds owing to their structural variations and potential to be exploited for diverse biological applications. Many diseases, including the recent COVID-19 pandemic - caused by consecutive waves of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants - continue to have significant impact on healthcare systems worldwide. This Research Topic contains a collection of articles that include computational studies (particularly molecular docking to predict binding affinities and interactions of ligands to specific protein targets) and in vitro biological testing to evaluate the pharmacological potential of metal-complexed molecules

Bioactive natural compounds from Prosopis africana and Abies nobili

Chromatographic procedures from the aerial parts of Abies nobilis and stem barks of Prosopis africana led to the isolation of two (antimicrobial and cytotoxic) compounds. Their structures were established as 7, 3’, 4’-trihydroxy-3-methoxyflavanone and dehydroabietic acid on the basis of spectroscopic techniques

Human natural killer (NK) cell activation by luteolin from Brucea javanica leaves

There is growing interest in using natural substances from plants to potentially enhance anticancer activity. A key target in this respect is natural killer (NK) cells in order to generate an anticancerimmune response. Luteolin used in this study was derived from a local plant Brucea javanica leaves extract; through a bioassay-guided fractionation. The expression of interleukin-2 (IL-2) and interferon-γ (IFN-γ) was increased after 20 h treatment of 0.1 µM luteolin in human mixed lymphocytes, which reflects the activation of NK cells. This was further confirmed in co-culture experiments. NK cellinduced K562 target cell death was increased in the presence of luteolin. These results show that luteolin activates NK cells to kill target cells indicating the potential use of luteolin as an anticancer immunostimulant

Antibiofilm activity of heather and manuka honeys and antivirulence potential of some of their constituents on the DsbA1 enzyme of pseudomonas aeruginosa

Heather honey was tested for its effect on the formation of biofilms by Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, Salmonella Enteriditis and Acinetobacter baumanii in comparison with Manuka honey. At 0.25 mg/mL, Heather honey inhibited biofilm formation in S. aureus, A. baumanii, E. coli, S. Enteriditis and P. aeruginosa, but promoted the growth of E. faecalis and K. pneumoniae biofilms. Manuka honey inhibited biofilm formation in K. pneumoniae, E. faecalis, and S. Enteriditis, A. baumanii, E. coli and P. aeruginosa, but promoted S. aureus biofilm formation. Molecular docking with Autodock Vina was performed to calculate the predictive binding affinities and ligand efficiencies of Manuka and Heather honey constituents for PaDsbA1, the main enzyme controlling the correct folding of virulence proteins in Pseudomonas aeruginosa. A number of constituents, including benzoic acid and methylglyoxal, present in Heather and/or Manuka honey, revealed high ligand efficiencies for the target enzyme. This helps support, to some extent, the decrease in P. aeruginosa biofilm formation observed for such honeys

Editorial : Re-emergence of neglected tropical diseases amid the COVID-19 pandemic: epidemiology, transmission, mitigation strategies, and recent advances in chemotherapy and vaccines

Neglected tropical diseases (NTDs) are a group of infectious diseases that are common in the tropical regions of the world that include landmasses surrounding the equator such as North America, South America, Africa, Asia, and Australia. NTDs are caused by different microorganisms including bacteria, viruses, fungi, and parasites. Many NTDs involve specific environmental conditions, vectors, and animal reservoirs that favor the survival of microorganisms with complex life cycles. The vast majority of NTDs are caused by parasites followed by bacterial species, fungi, and viruses. Additionally, vector-borne arthropods like mites causing scabies and other ectoparasites can cause NTDs