AQUEOUS EXTRACTS FROM THE BULBS OF TULBAGHIA VIOLACEA ARE ANTIFUNGAL AGAINST ASPERGILLUS FLAVUS

Abstract

Aspergillus flavus is a cosmopolitan fungal pathogen that is often implicated in food spoilage and in aspergillosis infections in immunocompromised individuals. The current study was undertaken to assess the effect of aqueous bulb extracts of Tulbaghia violacea on A. flavus spore survival. The broth dilution assay was used to determine that the minimum inhibitory concentration (MIC) of the extract against A. flavus was 15 mg/mL and that the minimum fungicidal concentration (MFC) was 20 mg/mL. During well diffusion assays A. flavus was inhibited by a minimal extract concentration of 60 mg/mL. As expected, inhibition zones during well diffusion assays increased with increasing extract concentrations. The 2,3‐bis(2‐methoxy‐4‐nitro‐5‐sulfophenyl)‐5‐([phenylamino] carbonyl)‐2H‐tetrazolium hydroxide (XTT) assay showed a direct proportional decrease in metabolic activity of A. flavus with an increase in extract concentration. Inhibition of metabolic activity was quantifiable as early as 12 h after spore inoculation. This was in contrast to the broth dilution assay where inhibition only became clearly observable 48 h after spore inoculation. The antifungal nature of T. violacea aqueous bulb extracts against A. flavus 2527 shown here for the first time indicates a potential use of this extract as an effective antifungal agent against Aspergillus species. The extract could possibly be used in the future for reducing Aspergillus contamination of plant‐derived foods. PRACTICAL APPLICATIONS Tulbaghia violacea (wild garlic) is a well‐known, indigenous ornamental plant in South Africa whose biological activities including a reduction in blood pressure has been previously documented. It is often eaten by African people for alleviating symptoms of high blood pressure including headaches. The plant is therefore safe to consume and appears to have no toxicological effects. With an ever‐increasing population and increasing cost of maintaining a constant and effective food supply, the natural antifungal agents found in aqueous extracts of T. violacea may provide an inexpensive means of reducing food spoilage by Aspergillus spp.

Aqueous Extracts of Tulbaghia violacea Inhibit Germination of Aspergillus flavus and Aspergillus parasiticus Conidia

“…In at least one case, both fungal growth and mycotoxin production in A. parasiticus (18) was inhibited by plant essential oils. In various studies, T. violácea extracts exhibited antifungal activity against a variety of fungi (5,9,13,14). In various studies, T. violácea extracts exhibited antifungal activity against a variety of fungi (5,9,13,14).…”

“…Cultivated T. violácea plants were obtained, and aqueous extracts were made as previously described (5). Cultivated T. violácea plants were obtained, and aqueous extracts were made as previously described (5).…”

Assessment of the antifungal activity of Spirulina platensis phenolic extract against Aspergillus flavus

“…Because of prolonged or overuse of some fungicides, many plant pathogens have developed resistance toward many synthetic chemicals, thereby rendering the fungicide ineffective (PÉRET-ALMEIDA et al, 2008;BELEWA et al, 2011;MEDEIROS et al, 2011).…”

The effect of storage and processing on antimicrobial activity of Tulbaghia violacea

“…However, there are considerable discrepancies in the antimicrobial assay results reported. Whereas some authors have found the plant to be completely devoid of antimicrobial activity (McGaw et al, 2000;Bamuamba et al, 2008;Nyila et al, 2012), others have observed significant antimicrobial properties in various Tulbaghia extracts (Motsei et al, 2003;Lindsey and Van Staden, 2004;Thamburan et al, 2006;Nteso and Pretorius, 2006a,b;Buwa and Afolayan, 2009;Belewa et al, 2011;Somai and Belewa, 2011;Jäger and Stafford, 2012;Soyingbe et al, 2013).…”