Antifungal and cytotoxic activities of acetone and aqueous extracts of Morinda lucida

Abstract

Aspergillosis is an opportunistic airborne fungal infection caused by ubiquitous saprophytic moulds of the Aspergillus genus. Infection has been documented in humans and animals, and it usually occurs through inhalation of unicellular spores known as conidia or, more rarely, after ingestion or wound contamination. Oral candidiasis is also an important sign for clinical diagnosis and an indicator of the evolution of immunodeficiency among HIV carriers. Mycotic stomatitis in animals is caused by Candida spp. in most cases. Cryptococcosis is a fungal disease of man and domestic animals, caused by the Cryptococcus neoformans complex. In animals it is often characterized by upper respiratory symptoms, subcutaneous nodules, pneumonia, central nervous system or ocular disorders, lymphadenopathy, or subcutaneous nodules. Antifungal drugs are often unaffordable to rural farmers and their efficacy is hampered as a result of antimicrobial resistance. Therefore, the need to seek alternative measures from phytogenic sources is urgent. The aim of this study was to investigate the in vitro antifungal activity of acetone and aqueous extracts of Morinda lucida (Rubiaceae) against ATCC strains of Aspergillus fumigatus, A. flavus, Candida albicans and Cryptococcus neoformans as well as clinical isolates of A. fumigatus and C. albicans using a serial microdilution assay. The cytotoxicity against human colon cancer (Caco‐2) cells and total activity of the acetone and aqueous extracts were also determined. The minimum inhibitory concentration (MIC) of both extracts against tested organisms ranged from 0.11 to 2.50 mg/ml and 0.03 to 2.50 mg/ml after 48 and 72 hours respectively. The LC50 values of the acetone and aqueous extracts against the Caco‐2 cells were 0.46 and 0.58 mg/ml respectively. The range of selectivity index (SI) values of both extracts was 0.23 to 5.27 and 0.23 to 19.33 after 48 and 72 hours respectively. The range of total activity of the extracts was 56 to 2 454 and 56 to 9 000 ml/g after 48 and 72 hours respectively. The potential of this plant species as an alternative for treatment of human and livestock mycoses is supported by these results. However, in vivo data is necessary to further investigate this claim