Advances in Microbiology, Infectious Diseases and Public Health by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9783030536473
Publisher: Springer International Publishing

3 Antifungal Natural Products

The adverse antifungal therapy reactions, in association with the high rate of multi-resistant pathogens, require the development of new remedies for the treatment of fungal infections. Furthermore, the intensive use of fungicides in agriculture, food industry, etc. causes essential damage to both the environment and human health. For that reason, the natural compounds with antifungal activity have become an attractive alternative over the past two decades. There are several classes of phytochemicals with antifungal activity: terpenes, tannins, flavonoids, alkaloids, lecithin, various polypeptides and others (Castillo et al. 2012).

Plants produce a variety of medicinal components that can inhibit pathogen growth. A considerable number of studies of medicinal plants and alternative compounds, such as secondary metabolites, phenolic compounds, essential oils and extracts, have been performed (Negri et al. 2014). Most of the antifungal compounds of plant origin belong to the phenol category. This group is extremely heterogeneous, including over 10 thousand compounds, a large part of them present in leaf extracts, tree bark, wood, fruits and other tissues of fern, gymnosperm and angiosperm plants. Phenols perform important functions, like resistance to microorganisms (including fungi), insects and herbivorous animals that can affect them. In particular, polyphenols have strong antioxidant properties, making them active in the fight against stress and free radicals, maintaining plant integrity in the process of continuous exposure to ultraviolet radiation, relatively high temperatures and dehydration.

Plant phenolic compounds display high antifungal activity against various species (Penicillium italicum, Penicillium expansum, Monilinia laxa, Aspergillus carbonarius, Botrytis cinerea, Monilinia fructicola and others) (Gatto et al. 2013). Phenol action on yeasts differs from the mode of action on filamentous fungi (Ansari et al. 2013). Thus, Candida dimorphic species are affected by phenolic compounds in the process of transition from one form to another. For example, phenolic compounds of Baseonema acuminatum leaves, Lycium chinense, Sida urens, and Curcuma longa root bark have shown strong antifungal activity against various Candida albicans strains. Their effect is associated with an increase in the amount of reactive species of oxygen and nitrogen in fungal cells, with predominant location in membrane, which induces early apoptosis. It is very important that the effects are irreversible and cannot be removed by the action of antioxidants (Ansari et al. 2013; Zerbo et al. 2014).

The extract from Curcuma longa is extremely effective against C. albicans strains. The mechanism of antifungal effect is based on inhibition of desaturase expression (ERG3), leading to a significant reduction of ergosterol in fungal cells. Accumulation of biosynthetic precursors of ergosterol in cells leads to cell death by the generation of reactive oxygen species (ROSs). Thus, the curcumin, bisbibenzyl, carvacrol and thymol compounds have been successfully used in the candidiasis treatment, through their effects on dimorphic transformation, biofilm formation and ROS generation (Ansari et al. 2013).

Among the phenolic compounds, hydrolysable tannins are also recognized as antifungal agents. In particular, by their effect on filamentous fungi Epidermophyton floccosum, Microsporum canis, Microsporum gypseum, Trichophyton mentagrophytes, Trichophyton rubrum, Trichophyton tonsurans, Trichophyton terrestre, Penicillium italicum, Aspergillus fumigatus, Mucor racemosus, Rhizopus nigricans, as

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.