Members of the Fusarium solani and Fusarium oxysporum species complexes are the most implicated etiologic agents in opportunistic fusarial infections in mammals while Paecilomyces variotii is one of the most frequently encountered Paecilomyces species in human infections. Prevention and treatment of these mycoses are problematic because available antimycotics are limited and often have toxic side effects. Popular folk medicines, such as the inner leaf gel from Aloe spp., are potential sources for non-toxic novel antimycotic compounds.To screen for antifungal properties of a non-domesticated Aloe species, Aloe striata, germination assays with homogenized 0.2 µm filtered A. striata inner leaf gel were performed against conidia of 3 strains each of P. variotii, F. solani and F. oxysporum. Although exposure to A. striata inner leaf gel caused only minimal inhibition of conidial germination for all strains, it caused visible hyphal aberrations characterized by increased hyphal diameters that lead to intervals of non-parallel hyphal cell walls as well as increased parental cell diameters. Adhesion assay results indicated that A. striata inner leaf gel induced hyphal aberrations significantly contribute to a decrease in the ability of 3 P. variotii strains to successfully remain adhered to microscope slides.
To isolate and identify the fractions of A. striata inner leaf gel responsible for hyphal aberrations, a combination of chromatographic techniques was used. A reverse phase high performance liquid chromatography (RP-HPLC) generated fraction, fraction A, demonstrated the most significant induction of hyphal aberrations. When fraction A was further separated, we identified fraction AIa as the portion of fraction A that caused the most significant hyphal aberration frequency increase in P. variotii ATCC 22319.
Our findings implicate A. striata inner leaf gel fraction AIa as the source of hyphal aberration frequency increases in P. variotii, F. oxysporum, and F. solani. Since hyphal aberrations contribute to a decrease in adhesion frequency, an important fungal virulence factor, we have identified A. striata inner leaf gel fraction AIa as a mixture of compounds with novel antimycotic properties that could potentially be used to combat adhesion and help reduce and/or prevent fungal colonization of hosts and/or substrates.