Agricultural Research Council of Nigeria, Agricultural Research House, Plot 223D, Cadastral Zone B6, Mabushi District, Wuse Abuja, Nigeria
NOVEMBER 5-6, 2012
Control of Toxigenic Fungi and Aflatoxin with Botanicals
Aflatoxins (Aspergillus flavus toxins - B1, B2, G1 and G2) are biologically active secondary metabolites produced by certain strains of Aspergillus parasiticus, Aspergillus nominus and Aspergillus flavus (Cotty et al., 1994).
Toxigenic fungi – widely distributed in nature and can grow over a wide range of environmental conditions (Holmquist et al., 1983).
Aflatoxin contamination of crops is a worldwide food safety concern.
Aflatoxins detected in cereal grains, oil seeds, fermented beverages made from grains, milk, cheese, meat, nut products, fruit juice (Bullerman, 1986).
More than 280 plant species have been investigated for their inhibitory effect on toxigenic Aspergilli and nearly 100 of these plants had some activity on growth or toxin production by fungi (Montes and Carvajal, 1998).
An appropriate digestion, extraction and concentration of just about any crusted plant tissue will be toxic to other plants, animals or microorganism (Harper, 1977).
Plant leaves, stems, bark, bud, seeds or roots offer potential for fungi control through the production and release of toxic mixtures of phytocompounds/allelochemicals in them (Macias, 1998).
They are not essential or involved in the primary protoplasmic metabolism of the plants but are potentially toxic (Duke, 1997).
The objective of this presentation is to explain the protective effects of botanicals (raw plant products, phytochemicals, essential oil) against the growth of toxigenic Aspergillus, synthesis of aflatoxins as well as the damage of aflatoxins.
Justification for the use of phytofungicides
Vast fields in developing countries are blessed with abundant plants with fungicidal potential with preparation and application attracting lower capital investment than synthetic fungicides (Anjorin and Salako, 2009).
Rotimi and Moens (2003) reported that botanical pesticides are locally renewable, user-friendly and environmentally safe.
The knowledge and technology involved in using botanicals is embedded in folklores and tradition of the farmers (Anjorin and Salako, 2009).
Health hazards from exposure toxic synthetic fungicides and economic considerations make natural plant extracts ideal alternatives to protect food and feed from fungal contamination (Reddy et al., 2007).
Varieties of secondary metabolites in plants are tannins, terpenoids, alkaloids,and flavonoids, which have been found in vitro to have fungitoxicproperties, systemic in action and lack residual effect, (Naganawa et al., 1996; Kubo et al., 1995; Table 1). Hence antimicrobial properties of some plant constituents are being exploited in protecting food, feed and seeds from storage moulds (Centeno et al., 2010).
Such products from higher plants (azadirachtin from Azadirachta indica, eugenol from Syzygium aromaticum and allyl isothiocyanate from mustard) are biodegradable, exhibit stimulating effect on plant metabolism. and perhaps safer to human health (Varma and Dubey, 1999; Singh et al., 2008).