Potent antifungal activity of saponins from medicinal plants against candida albicans

Abstract

Candida albicans, is usually a harmless fungus in healthy individuals, but life-threatening when found in large quantities or in inappropriate parts of the body. It developed resistance against the antifungal drugs fluconazole and amphotericin B, used in an abusive way, by adopting different mechanisms. Medicinal plants, which offer a wide variety of secondary metabolites, especially saponins, have been reported for their large biological activities. These phytochemicals are composed of a hydrophobic part (aglycone) and a hydrophilic one (glycone), which, based on their aglycone part, are classified into either triterpenoid, or steroidal or alkaloidal saponins. The aim of this study is to investigate the role of saponins as an effective treatment against drug-resistant C. albicans. Broth microdilution and disk diffusion techniques were employed to determine the efficacy of the triterpenoid and steroidal saponins against C. albicans. Eventually, these phytochemicals, produced by different medicinal plants, have been found to have potent antifungal activities against C. albicans. These properties depend mainly on the type and number of sugars in the hydrophilic part. Also, some important aspects make saponins potent and very effective. The following are: the types and position of different functional groups, in the aglycone, which are essential for the proper functioning of the saponins against C. albicans. These functional groups may include hydroxyl, carboxyl, aldehyde, ketone and acetoxy groups. However, their positions on the sapogenin, and/or genin, and the effect they have on the compound differs among saponins. Each saponin has its own properties that enhance its antifungal effect. Also, monodesmosidic saponins are better antifungal agents than bidesmosidic ones. The triterpenoid saponin Anagallisin C with an oleanolic acid aglycone was found to be the most potent compound against C. albicans with an MIC of 1 μg/mL. Also, two steroidal saponins: TG-I, from Trillium grandiflorum and TTS-12 from Tribulus terrestris were able to exert great fungistatic activities against C. albicans. The former exhibited an MIC value of 1.56 μg/mL, as for the latter, it produced an MIC80 of 1 μg/mL. Thus, these three compounds together with other potent ones, could be used as alternatives to treat fungal infections caused by C. albicans. Eventually, circumventing the fast increase of antifungal resistance against the substantial use of the antifungal drugs fluconazole and amphotericin B.