In silico approach of secondary metabolites from Brazilian herbal medicines to search for potential drugs against SARS-CoV-2.

The new severe acute respiratory syndrome coronavirus (SARS-CoV-2) recently emerged as a worrying pandemic, with many confirmed cases and deaths globally. Therefore, there is a clear need for identifying effective therapeutic options and a review of secondary metabolites related to Brazilian herbal medicines was performed as a strategy for the discovery of new antiviral agents. To confirm this potential, an in silico screening of the identified compounds identified was also evaluated. The review was performed by the PubMed database and the selected natural compounds were subjected to in silico analysis such as QSAR, molecular docking and ADMET. 497 secondary metabolites were identified from 23 species. The in silico assays indicated 19 potential anti-SARS-CoV-2 compounds, being triterpenes and phenolic compounds. The indicated compounds showed a high affinity with proteins considered as the main molecular targets against SARS-CoV-2 and parameters indicated low toxicity. In addition to Brazilian medicinal plants, these compounds can be found in other species and they can be a base for the synthesis of other anti-COVID-19 drugs. Therefore, this review is important to conduct researches that address the emerging need for drugs in COVID-19 treatment.

Associating chitosan and microemulsion as a topical vehicle for the administration of herbal medicines.

A viscous solution of low molecular weight chitosan (CH) at 5% w/v (10.2 kDa, 75 % deacetylated, 1451 cP at 25 °C) was associated with a microemulsion (ME) that undergoes a phase transition after water absorption in situ (≈28 % w/w), forming a more viscous liquid crystal, which was potentially evaluated as a topical vehicle. The ME was selected from a phase diagram, selecting a composition based on Tween® 80 (52 %), myristate isopropyl (28 %), and the aqueous phase (water and polyethylene glycol 400, 60:40 w/w) (20 %), which was after replaced by CH and herbal medicines (HM). HM are alternatives to treat candidiasis, and Stryphnodendron adstringens shell extract, characterized by molecular networking, and Melaleuca alternifolia Chell essential oil (46 % of terpinen-4-ol), showed in vitro activity against Candida albicans. Associating CH in ME improved the mechanical properties of the topical formulation, as adhesiveness, which is an advantageous feature for the topical treatment of vulvovaginal candidiasis.

Melaleuca leucadendra Essential Oil Promotes Loss of Cell Membrane and Wall Integrity and Inhibits Bacterial Growth: An In Silico and In Vitro Approach.

Essential oils are potential antimicrobial agents and can be used as active ingredients in the pharmaceutical, food and cosmetics industries. This work intends to evaluate the antibacterial activity and design a strategy for the proposition of the mechanism of action of Melaleuca leucadendra essential oil. Optimum concentration of the bacteria and the phase where they had the highest pathogenic activity were determined. Results show that for each microorganism it is necessary to use a different concentration at the time of adjusting the initial inoculum, and that the time to achieve exponential growth phase varies from one to the other. M. leucadendra essential oil demonstrated in vitro antimicrobial properties. This oil was chemically characterized and the main compounds were evaluated by their mechanism of antibacterial action based on structure-activity analysis. The mechanism is related to the increase of bacteria cell membrane permeability. This indication was confirmed by flow cytometry and transmission electronic microscopy. Thus, in silico analysis is an important tool in the search for new antimicrobial agents and these results showed that M. leucadendra essential oil may be useful on the development of new chemotherapies or food preservation systems.

Nanostructured Systems Improve the Antimicrobial Potential of the Essential Oil from Cymbopogon densiflorus Leaves.

The physicochemical characteristics of nanostructured suspensions are important prerequisites for the success of new drug development. This work aimed to develop nanometric systems containing Cymbopogon densiflorus leaf essential oil and to evaluate their antimicrobial activity. The essential oil was isolated by hydrodistillation from leaves and analyzed by GC-MS. The main constituents were found to be trans-p-mentha-2,8-dien-1-ol, cis-p-mentha-2,8-dien-1-ol, trans-p-mentha-1(7),8-dien-2-ol, cis-piperitol, and cis-p-mentha-1(7),8-dien-2-ol. In silico prediction analysis suggested that this oil possesses antimicrobial potential and the main mechanism of action might be the peptidoglycan glycosyltransferase inhibition. Nanoemulsions were prepared by the phase inversion method, and liposomes were made by the film hydration method. Qualitative evaluation of the antimicrobial activity was performed by the diffusion disk assay with 24 microorganisms; all of them were found to be sensitive to the essential oil. Subsequently, this property was quantified by the serial microdilution technique, where the nanoformulations demonstrated improved activity in comparison with the free oil. Bactericidal action was tested by the propidium iodide method, which revealed that free essential oil and nanoemulsion increased cytoplasmic membrane permeability, while no difference was observed between negative control and liposome. These results were confirmed by images obtained using transmission electron microscopy. This study has shown an optimization in the antimicrobial activity of C. densiflorus essential oil by a nanoemulsion and a liposomal formulation of the active substances.

Preparation and in vitro evaluation of α and ß-amyrins loaded nanoemulsions.

The triterpenes α- and ß-amyrins display important pharmacological activities. As a result of their high hydrophobia, they present low water solubility and reflect poor oral bioavailability. Different techniques can be used for the improvement of amyrins solubility, one of them is the use of nanoemulsions. Therefore, the method of direct emulsification was used to develop a nanoemulsion of these triterpenes and the resulting drug delivery system was characterized by an in vitro release assay. Encapsulation efficiency higher than 99% was achieved with total release around 30% in 24 h, which suggests that this system could be useful for the administration of α- and ß-amyrins by different routes in an efficient way.