Current Understanding of the Molecular Basis of Spices for the Development of Potential Antimicrobial Medicine.

Antimicrobial resistance increases day by day around the world. To overcome this situation new antimicrobial agents are needed. Spices such as clove, ginger, coriander, garlic, and turmeric have the potential to fight resistant microbes. Due to their therapeutic properties, medicinal herbs and spices have been utilized as herbal medicines since antiquity. They are important sources of organic antibacterial substances that are employed in treating infectious disorders caused by pathogens such as bacteria. The main focus of the study is the bioactivity of the active ingredients present in different kinds of naturally available spices. We conducted a thorough search of PubMed, Google Scholar, and Research Gate for this review. We have read many kinds of available literature, and in this paper, we conclude that many different kinds of naturally available spices perform some form of bioactivity. After reading several papers, we found that some spices have good antimicrobial and antifungal properties, which may help in controlling the emerging antimicrobial resistance and improving human health. Spices have many phytochemicals, which show good antimicrobial and antifungal effects. This review of the literature concludes that the natural bioactivate compounds present in spices can be used as a drug to overcome antimicrobial resistance in human beings.

Mechanistic insights into the antimycobacterial action of unani formulation, Qurs Sartan Kafoori.

Background and aim: Tuberculosis (TBC) is a deadly disease and major health issue in the world. Emergence of drug resistant strains further worsens the efficiency of available anti-TBC drugs. Natural compounds and particularly traditional medicines such as Unani drugs are one of the promising alternatives that have been widely used nowadays. This study aims to evaluate the efficacy of unani drug Qurs-e-Sartan Kafoori (QSK) on Mycobacterium tuberculosis (MTB). Experimental procedures: Drug susceptibilities were estimated by broth microdilution assay. Cell surface integrity was assessed by ZN staining, colony morphology and nitrocefin hydrolysis. Biofilms were visualized by crystal violet staining and measurement of metabolic activity and biomass. Lipidomics analysis was performed using mass spectrometry. Host pathogen interaction studies were accomplished using THP-1 cell lines to estimate cytokines by ELISA kit, apoptosis and ROS by flow cytometry. Results: QSK enhanced the susceptibilities of isoniazid and rifampicin and impaired membrane homeostasis as depicted by altered cell surface properties and enhanced membrane permeability. In addition, virulence factor, biofilm formation was considerably reduced in presence of QSK. Lipidomic analysis revealed extensive lipid remodeling. Furthermore, we used a THP-1 cell line model, and investigated the immunomodulatory effect by estimating cytokine profile and found change in expressions of TNF-α, IL-6 and IL-10. Additionally, we uncover reduced THP-1 apoptosis and enhanced ROS production in presence of QSK. Conclusion: Together, this study validates the potential of unani formulation (QSK) with its mechanism of action and attempts to highlight its significance in MDR reversal.

Essential Oils as Alternative Promising Anti-Candidal Agents: Progress and Prospects.

Candida albicans is one of the main agents responsible for opportunistic pathogenic infections. The progressive emergence of fungal resistance to conventional antibiotics and its side effects, as well as treatment costs, are considered major limitations for antifungal drugs. It has drawn scientists' attention to the search for potential substitution and reliable therapeutic alternatives for the antifungal compounds from sources like medicinal plants, which contain numerous bioactive compounds such as essential oils. Essential oils (EO), apart from having lower toxicity and better biodegradability, are eco-friendly in nature as compared with conventional antibiotics. Furthermore, extracted essential oils have been reported to possess potent antimicrobial, antiinflammatory, and antioxidant properties that nominate them as promising natural candidates to combat numerous fungal ailments. Thus, the determination of antifungal efficacy of essential oil-bearing plants on Candida spp. will provide miscellaneous knowledge for future clinical studies that are required for the development of new formulations as alternative therapeutic agents to control the growth of Candida species. Therefore, this review summarizes the gist of major essential oils that have been investigated for their anti- Candida potential with some recommendations for further study.

Understanding Human Microbiota Offers Novel and Promising Therapeutic Options against Candida Infections.

Human fungal pathogens particularly of Candida species are one of the major causes of hospital acquired infections in immunocompromised patients. The limited arsenal of antifungal drugs to treat Candida infections with concomitant evolution of multidrug resistant strains further complicates the management of these infections. Therefore, deployment of novel strategies to surmount the Candida infections requires immediate attention. The human body is a dynamic ecosystem having microbiota usually involving symbionts that benefit from the host, but in turn may act as commensal organisms or affect positively (mutualism) or negatively (pathogenic) the physiology and nourishment of the host. The composition of human microbiota has garnered a lot of recent attention, and despite the common occurrence of Candida spp. within the microbiota, there is still an incomplete picture of relationships between Candida spp. and other microorganism, as well as how such associations are governed. These relationships could be important to have a more holistic understanding of the human microbiota and its connection to Candida infections. Understanding the mechanisms behind commensalism and pathogenesis is vital for the development of efficient therapeutic strategies for these Candida infections. The concept of host-microbiota crosstalk plays critical roles in human health and microbiota dysbiosis and is responsible for various pathologies. Through this review, we attempted to analyze the types of human microbiota and provide an update on the current understanding in the context of health and Candida infections. The information in this article will help as a resource for development of targeted microbial therapies such as pre-/pro-biotics and microbiota transplant that has gained advantage in recent times over antibiotics and established as novel therapeutic strategy.

Protein kinases as potential anticandidal drug targets.

Candidal infections are increasing at an alarming rate due to hospital acquired infections causing high mortality rates worldwide. Moreover, the emergence of drug resistant Candida strains is the major impediment against effective therapeutics. Thus, there is an imperious need to search for novel antifungal drug targets. Among various fungi, Candida albicans is one of  the most prevalent human fungal pathogen. Protein kinases modify other signaling molecules through phosphorylation and transduce extracellular stimuli for adaptation ensuing C. albicans growth, persistence and pathogenesis. In C. albicans, there are various kinds of kinases such as MAP (Mitogen Activated Protein) kinase cascade involving Hog1 (High-osmolarity glycerol) and Cek1 (C. albicans ERK-like Kinase1) mediated pathways, cyclin dependent pathway, cAMP (cyclic adenosine monophosphate) -dependent protein kinase pathway and TOR signaling pathway. Herein we have reviewed the variety of functions served by protein kinases in C. albicans.  Additionally, we have discussed the inhibitors for targeting these kinases. Together, we explore the potential of these kinases as effective drug target and discuss the progress made in the development of inhibitors against these targets.

Insights into the mode of action of anticandidal herbal monoterpenoid geraniol reveal disruption of multiple MDR mechanisms and virulence attributes in Candida albicans.

The anticandidal potential of Geraniol (Ger) against Candida albicans has already been established. The present study reveals deeper insights into the mechanisms of action of Ger. We observed that the repertoire of antifungal activity was not only limited to C. albicans and its clinical isolates but also against non-albicans species of Candida. The membrane tampering effect was visualized through transmission electron micrographs, depleted ergosterol levels and altered plasma membrane ATPase activity. Ger also affects cell wall as revealed by spot assays with cell wall-perturbing agents and scanning electron micrographs. Functional calcineurin pathway seems to be indispensable for the antifungal effect of Ger as calcineurin signaling mutant was hypersensitive to Ger while calcineurin overexpressing strain remained resistant. Ger also causes mitochondrial dysfunction, impaired iron homeostasis and genotoxicity. Furthermore, Ger inhibits both virulence attributes of hyphal morphogenesis and biofilm formation. Taken together, our results suggest that Ger is potential antifungal agent that warrants further investigation in clinical applications so that it could be competently employed in therapeutic strategies to treat Candida infections.

Antifungal Action of Methylene Blue Involves Mitochondrial Dysfunction and Disruption of Redox and Membrane Homeostasis in C. albicans.

Candida albicans is known to cause infections ranging from superficial and systemic in immunocompromised person. In this study, we explored that the antifungal action of Methylene blue (MB) is mediated through mitochondrial dysfunction and disruption of redox and membrane homeostasis against C. albicans. We demonstrated that MB displayed its antifungal potential against C. albicans and two clinical isolates tested. We also showed that MB is effective against two non- albicans species as well. Notably, the antifungal effect of MB seems to be independent of the major drug efflux pumps transporter activity. We explored that MB treated Candida cells were sensitive on non-fermentable carbon source leading us to propose that MB inhibits mitochondria. This sensitive phenotype was reinforced with the fact that sensitivity of Candida cells to MB could be rescued upon the supplementation of ascorbic acid, an antioxidant. This clearly suggests that disturbances in redox status are linked with MB action. We further demonstrated that Candida cells were susceptible to membrane perturbing agent viz. SDS which was additionally confirmed by transmission electron micrographs showing disruption of membrane integrity. Moreover, the ergosterol levels were significantly decreased by 66% suggesting lipid compositional changes due to MB. Furthermore, we could demonstrate that MB inhibits the yeast to hyphal transition in C. albicans which is one of the major virulence attribute in most of the hyphal inducing conditions. Taken together, the data generated from present study clearly establishes MB as promising antifungal agent that could be efficiently employed in strategies to treat Candida infections.

Therapeutic Potential of Dietary Phenolic Acids.

Although modern lifestyle has eased the quality of human life, this lifestyle's related patterns have imparted negative effects on health to acquire multiple diseases. Many synthetic drugs are invented during the last millennium but most if not all of them possess several side effects and proved to be costly. Convincing evidences have established the premise that the phytotherapeutic potential of natural compounds and need of search for novel drugs from natural sources are of high priority. Phenolic acids (PAs) are a class of secondary metabolites spread throughout the plant kingdom and generally involved in plethora of cellular processes involved in plant growth and reproduction and also produced as defense mechanism to sustain various environmental stresses. Extensive research on PAs strongly suggests that consumption of these compounds hold promise to offer protection against various ailments in humans. This paper focuses on the naturally derived PAs and summarizes the action mechanisms of these compounds during disease conditions. Based on the available information in the literature, it is suggested that use of PAs as drugs is very promising; however more research and clinical trials are necessary before these bioactive molecules can be made for treatment. Finally this review provides greater awareness of the promise that natural PAs hold for use in the disease prevention and therapy.

Iron Deprivation Affects Drug Susceptibilities of Mycobacteria Targeting Membrane Integrity.

Multidrug resistance (MDR) acquired by Mycobacterium tuberculosis (MTB) through continuous deployment of antitubercular drugs warrants immediate search for novel targets and mechanisms. The ability of MTB to sense and become accustomed to changes in the host is essential for survival and confers the basis of infection. A crucial condition that MTB must surmount is iron limitation, during the establishment of infection, since iron is required by both bacteria and humans. This study focuses on how iron deprivation affects drug susceptibilities of known anti-TB drugs in Mycobacterium smegmatis, a "surrogate of MTB." We showed that iron deprivation leads to enhanced potency of most commonly used first line anti-TB drugs that could be reverted upon iron supplementation. We explored that membrane homeostasis is disrupted upon iron deprivation as revealed by enhanced membrane permeability and hypersensitivity to membrane perturbing agent leading to increased passive diffusion of drug and TEM images showing detectable differences in cell envelope thickness. Furthermore, iron seems to be indispensable to sustain genotoxic stress suggesting its possible role in DNA repair machinery. Taken together, we for the first time established a link between cellular iron and drug susceptibility of mycobacteria suggesting iron as novel determinant to combat MDR.

Calcineurin signaling and membrane lipid homeostasis regulates iron mediated multidrug resistance mechanisms in Candida albicans.

We previously demonstrated that iron deprivation enhances drug susceptibility of Candida albicans by increasing membrane fluidity which correlated with the lower expression of ERG11 transcript and ergosterol levels. The iron restriction dependent membrane perturbations led to an increase in passive diffusion and drug susceptibility. The mechanisms underlying iron homeostasis and multidrug resistance (MDR), however, are not yet resolved. To evaluate the potential mechanisms, we used whole genome transcriptome and electrospray ionization tandem mass spectrometry (ESI-MS/MS) based lipidome analyses of iron deprived Candida cells to examine the new cellular circuitry of the MDR of this pathogen. Our transcriptome data revealed a link between calcineurin signaling and iron homeostasis. Among the several categories of iron deprivation responsive genes, the down regulation of calcineurin signaling genes including HSP90, CMP1 and CRZ1 was noteworthy. Interestingly, iron deprived Candida cells as well as iron acquisition defective mutants phenocopied molecular chaperone HSP90 and calcineurin mutants and thus were sensitive to alkaline pH, salinity and membrane perturbations. In contrast, sensitivity to above stresses did not change in iron deprived DSY2146 strain with a hyperactive allele of calcineurin. Although, iron deprivation phenocopied compromised HSP90 and calcineurin, it was independent of protein kinase C signaling cascade. Notably, the phenotypes associated with iron deprivation in genetically impaired calcineurin and HSP90 could be reversed with iron supplementation. The observed down regulation of ergosterol (ERG1, ERG2, ERG11 and ERG25) and sphingolipid biosynthesis (AUR1 and SCS7) genes followed by lipidome analysis confirmed that iron deprivation not only disrupted ergosterol biosynthesis, but it also affected sphingolipid homeostasis in Candida cells. These lipid compositional changes suggested extensive remodeling of the membranes in iron deprived Candida cells. Taken together, our data provide the first novel insight into the intricate relationship between cellular iron, calcineurin signaling, membrane lipid homeostasis and drug susceptibility of Candida cells.

Iron deprivation induces EFG1-mediated hyphal development in Candida albicans without affecting biofilm formation.

In this study, we investigated the role of cellular iron status in hyphae and biofilm formation in Candida albicans. Iron deprivation by a chelator, bathophenanthrolene disulfonic acid, promoted hyphal development even in nonhyphal-inducing media without affecting growth of C. albicans cells. Iron-acquisition defective mutants, Deltaftr1 and Deltaccc2, also showed hyphal formation, which was prevented by iron supplementation. Notably, most of the tested morphological mutants Deltacph1, Deltaefh1 and Deltatpk1 continued to form hyphae under iron-deprived conditions, except the Deltaefg1 null mutant, which showed a complete block in hyphae formation. The role of EFG1 in filamentation under iron-deprived conditions was further confirmed by Northern analysis, which showed a considerable upregulation of the EFG1 transcript. Of notable importance, all the morphological mutants including Deltaefg1 mutant possessed enhanced membrane fluidity under iron-deprived conditions; however, this did not appear to contribute to hyphal development. Interestingly, iron deprivation did not affect the ability of C. albicans to form biofilms on the catheter surface and led to no gross defects in azole resistance phenotype of these biofilms of C. albicans cells. Our study, for the first time, establishes a link between cellular iron, Efg1p and hyphal development of C. albicans cells that is independent of biofilm formation.