Evaluating the anti-fungal properties of indigenous plant species

Abstract

Cryptococcosis, a common AIDS-defining illness, is diagnosed annually in approximately 215,000 people across the globe and has a mortality rate as high as 70%. Until recently, early diagnosis and the administration of antifungals had resulted in successful treatment; however, reports of increased resistance of these pathogens against standard azole therapies have begun to surface. This resistance shift has prompted the investigation into the use of medicinal plants as an alternative antifungal therapy, particularly those that are able to target known virulence factors and inhibit disease progression. In Chapter 1 the increase in cryptococcal-related diseases and the therapeutic approaches currently employed to treat them is discussed. This is followed by outlining the resistance mechanisms used by pathogenic Cryptococcus species and the potential of medicinal plants to serve as novel antifungal alternatives against them. In Chapter 2 three indigenous medicinal plants were screened, namely Agathosma betulina (Buchu), Hypoxis hemerocallidea (African potato) and Kigelia africana (Sausage tree), for antifungal activity (fungistatic and fungicidal) and their ability to inhibit ergosterol production. Data indicated that ethanolic K.africana extracts yielded the most effective growth inhibition overall with C. gattii being the most susceptible to this extract. In Chapter 3 the antivirulence property of ethanolic K. africana extract against all four pathogenic Cryptococcus species was assessed. Laccase activity was significantly inhibited in C. deneoformans and C. gattii, while urease activity in C. neoformans and C. tetragattii was significantly inhibited by plant bioactives. Overall, the application of ethanolic K. africana was identified as a promising alternative therapeutic with strong antifungal and antivirulence activity. Future work identifying specific metabolites and mechanisms of action are recommended