Agar sublimation test for the in vitro determination of the antifungal activity of morpholine derivatives. Agar-Sublimations-Test zur In vitro-Bestimmung der antimykotischen Aktivitat von Morpholin-Derivaten

Activity of amorolfine or ciclopirox in combination with terbinafine against pathogenic fungi in onychomycosis-Results of an in vitro investigation

BACKGROUND

Onychomycoses are difficult-to-treat fungal infections with high relapse rates. Combining oral and topical antifungal drugs is associated with higher success rates. Additive or synergistic modes of action are expected to enhance treatment success rates.

OBJECTIVES

Investigation of the combined effects of antifungal drugs in vitro with different modes of action and application on clinical isolates from mycotic nails.

METHODS

Isolates of Trichophyton rubrum, Trichophyton interdigitale and Scopulariopsis brevicaulis were collected from infected toenail specimens of patients with onychomycosis. Susceptibility testing was performed in 96-well polystyrene plates using a standard stepwise microdilution protocol. Additive or synergistic activity at varying concentrations was investigated by the checkerboard method.

RESULTS

Combining terbinafine with amorolfine tended to be more effective than terbinafine in conjunction with ciclopirox. In most combinations, additive effects were observed. Synergy was detected in combinations with involving amorolfine in S. brevicaulis. These additive and synergistic interactions indicate that combined therapy with topical amorolfine and oral terbinafine is justified. Sublimation of amorolfine (and terbinafine) may enhance the penetration in and through the nail plate, and support treatment efficacy.

CONCLUSIONS

These in vitro results support the notion that combining oral terbinafine and topical amorolfine is beneficial to patients with onychomycosis, particularly if the pathogen is a non-dermatophyte fungus such as S. brevicaulis.

Bioactive antifungal metabolites produced by Streptomyces amritsarensis V31 help to control diverse phytopathogenic fungi

Actinomycetes due to their unique repertoire of antimicrobial secondary metabolites can be an eco-friendly and sustainable alternative to agrochemicals to control plant pathogens. In the present study, antifungal activity of twenty different actinomycetes was evaluated via dual culture plate assay against six different phytopathogens, viz., Alternaria alternata, Aspergillus flavus, Fusarium oxysporum f. sp. lycopersici, Sarocladium oryzae, Sclerotinia sclerotiorum, and Rhizoctonia solani. Two potential isolates, Streptomyces amritsarensis V31 and Kribella karoonensis MSCA185 showing high antifungal activity against all six fungal pathogens, were further evaluated after extraction of bioactive metabolites in different solvents. Metabolite extracted from S. amritsarensis V31 in different solvents inhibited Rhizoctonia solani (7.5-65%), Alternaria alternata (5.5-52.7%), Aspergillus flavus (8-30.7%), Fusarium oxysporum f. sp. lycopersici (25-44%), Sarocladium oryzae (11-55.5%), and Sclerotinia sclerotiorum (29.7-40.5%); 1000 D diluted methanolic extract of S. amritsarensis V31 showed growth inhibition against R. solani (23.3%), A. flavus (7.7%), F. oxysporum (22.2%), S. oryzae (16.7%), and S. sclerotiorum (19.0%). Metabolite extracts of S. amritsarensis V31 significantly reduced the incidence of rice sheath blight both as preventive and curative sprays. Chemical profiling of the metabolites in DMSO extract of S. amritsarensis V31 revealed 6-amino-5-nitrosopyrimidine-2,4-diol as the predominant compound present. It was evident from the LC-MS analyses that S. amritsarensis V31 produced a mixture of potential antifungal compounds which inhibited the growth of different phytopathogenic fungi. The results of this study indicated that metabolite extracts of S. amritsarensis V31 can be exploited as a bio-fungicide to control phytopathogenic fungi.

A pilot, layerwise, ex vivo evaluation of the antifungal efficacy of amorolfine 5% nail lacquer vs other topical antifungal nail formulations in healthy toenails

BACKGROUND

Studies investigating the penetration of amorolfine through the nail have shown the highest concentration in the uppermost layer and measurable antifungal activity even in the lower layers of the nail.

OBJECTIVES

This pilot, ex vivo study compared the penetration of antifungal concentrations of amorolfine 5% nail lacquer in different layers of healthy, human cadaver toenails with that of terbinafine 10% nail solution, ciclopirox 8% nail lacquer and naftifine 1% nail solution. Moreover, the effect of nail filing prior to application on the penetration of amorolfine 5% was assessed.

METHODS

Unfiled (n = 3) and filed (n = 3) nails were used for each antimycotic agent and amorolfine 5% nail lacquer, respectively. Twenty-four hours after topical application, the nails were sliced (10 μm), solubilised and added to agar plates seeded with Trichophyton rubrum. Zones of growth inhibition were measured.

RESULTS

Only amorolfine penetrated the nails at sufficient concentrations to inhibit growth of T rubrum at different nail depths. In contrast, the comparators did not show antifungal efficacy. Nail filing resulted in larger zones of inhibition for amorolfine compared with those of intact nails.

CONCLUSIONS

Unlike its comparators, a single application of amorolfine 5% nail lacquer resulted in antifungal efficacy within the nail plate. Nail filing increased the antifungal efficacy of amorolfine 5% nail lacquer.

Chemical and physical strategies in onychomycosis topical treatment: A review

Onychomycosis is a fungal infection of the fingernails or toenails caused by dermatophytes, nondermatophytes, moulds, and yeasts. This condition affects around 10-30% people worldwide, negatively influencing patients' quality of life, with severe outcomes in some cases. Since the nail unit acts as a barrier to exogenous substances, its physiological features hampers drug penetration, turning the onychomycosis treatment a challenge. Currently, there are several oral and topical therapies available; nevertheless, cure rates are still low and relapse rates achieves 10-53%. Also, serious side effects may be developed due to long-term treatment. In light of these facts, researchers have focused on improving topical treatments, either by modifying the vehicle or by using some physical technique to improve drug delivery trough the nail plate, hence increasing therapy effectiveness. Therefore, the aim of this paper is to explain these novel alternative approaches. First, the challenges for drug ungual penetration are presented. Then, the chemical and physical strategies developed for overcoming the barriers for drug penetration are discussed. We hope that the information gathered may be useful for the development of safer and more effective treatments for onychomycosis.

Development of topical therapeutics for management of onychomycosis and other nail disorders: a pharmaceutical perspective

The human nail plate is a formidable barrier to drug permeation. Development of therapeutics for management of nail diseases thus remains a challenge. This article reviews the current knowledge and recent advances in the field of transungual drug delivery and provides guidance on development of topical/ungual therapeutics for management of nail diseases, with special emphasis on management of onychomycosis, the most common nail disease. Selection of drug candidates, drug delivery approaches, and evaluation of formulations are among the topics discussed. A comprehensive mathematical description for transungual permeation is also introduced.

Identification of novel N-(morpholine-4-carbonyloxy) amidine compounds as potent inhibitors against hepatitis C virus replication

To identify novel compounds that possess antiviral activity against hepatitis C virus (HCV), we screened a library of small molecules with various amounts of structural diversity using an HCV replicon-expressing cell line and performed additional validations using the HCV-JFH1 infectious-virus cell culture. Of 4,004 chemical compounds, we identified 4 novel compounds that suppressed HCV replication with 50% effective concentrations of ranging from 0.36 to 4.81 μM. N'-(Morpholine-4-carbonyloxy)-2-(naphthalen-1-yl) acetimidamide (MCNA) was the most potent and also produced a small synergistic effect when used in combination with alpha interferon. Structure-activity relationship (SAR) analyses revealed 4 derivative compounds with antiviral activity. Further SAR analyses revealed that the N-(morpholine-4-carbonyloxy) amidine moiety was a key structural element for antiviral activity. Treatment of cells with MCNA activated nuclear factor κB and downstream gene expression. In conclusion, N-(morpholine-4-carbonyloxy) amidine and other related morpholine compounds specifically suppressed HCV replication and may have potential as novel chemotherapeutic agents.