Current Topics in Medicinal Chemistry - Volume 22, Issue 13, 2022

The rapid emergence of multidrug--resistant bacterial strains highlights the need for the development of new antimicrobial compounds/materials to address associated healthcare challenges. Meanwhile, the adverse side effects of conventional antibiotics on human health urge the development of new natural product--based antimicrobials to minimize the side effects. In this respect, we concisely review the recent scientific contributions to develop natural product--based nano--antibiotics. The focus of the review is on the use of flavonoids, peptides, and cationic biopolymer functionalized metal/metal oxide nanoparticles as efficient tools to hit the MDR bacterial strains. It summarizes the most recent aspects of the functionalized nanoparticles against various pathogenic bacterial strains for their minimal inhibitory concentrations and mechanism of action at the cellular and molecular levels. In the end, the future perspectives to materialize the in vivo applications of nano--antimicrobials are suggested based on the available research.

The emerging outbreak of infectious diseases poses a challenge and threatens human survival. The indiscriminate use and drying pipelines of antibiotic arsenals have led to the alarming rise of drug-resistant pathogens, projecting a serious concern. The rising antimicrobial resistance and redundancy of antibiotic discovery platforms (ADPs) have highlighted the growing concern to discover new antibiotics, necessitating exploring natural products as effective alternatives to counter drug resistance. Recently, plants have been extensively investigated in search of the “phytotherapeutics”, attributed to their potential efficacy and tackling the majority of the drug-resistant mechanisms, including biofilms, efflux pumps, cell communication, and membrane proteins. However, major challenges in geographical fluctuations, low plant concentration, and over-harvestation of natural resources restrict availability and complete utilization of phyto-therapeutics as antimicrobials. Recent advances in scientific interventions have been instrumental in producing novel antimicrobials via metabolic engineering approaches in plant systems. The progress in plant genome editing, pathway reconstitution, and expression has defined new paradigms in the successful production of antimicrobials in the post-antibiotic era. The thematic review discusses the existing and emerging significance of phytotherapeutics in tackling antimicrobial resistance and employing metabolic engineering approaches. The prevailing scenario of antimicrobial resistance and the mechanisms, the traditional and modern drug-discovery approaches in addressing antimicrobial resistance, emphasizing advances in metabolic engineering approaches for antimicrobial production, and the plausible solutions for tackling drug-resistant pathogens, forms the key theme of the article.

The coevolution in microbes has generated major functional consequences leading bacteria to develop resistance to antibiotics. Indeed, bacterial strains have been able to develop and adapt to the action of antibiotics via several resistance mechanisms. In this context, researchers are currently conducting many studies to screen natural antibacterial substances such as secondary metabolites of medicinal plants. Indeed, the potential of many plants used in traditional medicine in the treatment of infectious diseases was confirmed experimentally, namely Anethum graveolens, Elettaria cardamomum, Foeniculum vulgare, Trachyspermum ammi, Viola odorata, Dioscorea dregeana, Cheilanthes viridis, Vernonia colorata, etc. Bioactive molecules from different medicinal plants include terpenoids, flavonoids, and phenolic acids, which were shown to have significant anti- bacterial effects. The mechanisms of action of these molecules are different and can include structural, cellular, and molecular levels, which suggests them as real candidates for the development of natural antibiotics. However, the clinical trials of these molecules have not been very well studied which limits their clinical use against infectious diseases of bacterial origin.

Background: Dandruff is a scalp disorder affecting the male populace predominantly. Topical agents and synthetic drugs used for dandruff treatment have specific side effects including burning at the application site, depression, dizziness, headache, itching or skin rash, nausea, stomach pain, vision change, vomiting, discoloration of hair, dryness or oiliness of the scalp and increased loss of hair. Thus, essential oils and extracts from plants could be valuable in the treatment and prevention of dandruff. Aims & Objectives: This review aims to highlight current findings in dandruff occurrence, its etiology, promising plant essential oils/extracts, and novel treatment strategies. The main emphasis has been given on the anti-dandruff effect of essential oils and plant extracts to disrupt microbial growth. The proposed mechanism(s) of action, novel approaches used to perk up its biopharmaceutical properties, and topical application have been discussed. Results: The literature survey was done, and bibliographic sources and research papers were retrieved from different search engines and databases, including SciFinder, PubMed, NCBI, Scopus, and Google Scholar. The selection of papers was accomplished based on exclusion and inclusion criteria. The scalp of diverse populations revealed an association of dandruff with microbial symbiosis, including Staphylococcus, Propionibacterium, Malassezia, and Candida as the pathogens responsible for the cause of dandruff. Topical antifungals are considered the first line of treatment for dandruff including azoles, with clotrimazole (1%), ketoconazole (2%), and miconazole (2%). Other commonly used therapies integrate benzoyl peroxide, coal tar, glycerin, zinc pyrithione, lithium succinate/gluconate, salicylic acid, selenium disulfide/sulfide, sodium sulfacetamide, etc. However, these medicaments and chemicals are known to cause specific side effects. Alternative therapies, including tea tree oil, thyme, Aloe vera, Mentha have been reported to demonstrate anti-dandruff activity by disrupting the microbial growth associated with dandruff formation. Conclusion: Overall, this review explains the occurrence of dandruff, its pathogenesis, and the potential applicability of promising plant essential oils/extracts and their novel treatment strategies. Further studies based on pre-clinical and clinical research are essential before making any conclusion about its efficacy in humans.