Antiaflatoxigenic and antioxidant activity of an essential oil from Ageratum conyzoides L

Aflatoxin contamination of various commodities can occur as a result of infection, mainly by Aspergillus flavus and Aspergillus parasiticus. Every year, almost 25% of the world's food supply is contaminated by mycotoxins. Aflatoxins B(1), B(2), G(1) and G(2), which occur naturally, are significant contaminants of a wide variety of commodities. A number of biological activities have been associated with Ageratum conyzoides. We have therefore investigated the antiaflatoxigenic, antioxidant and antimicrobial activity of essential oils of A. conyzoides. This could help to turn A. conyzoides, a nuisance weed, into a resource.

The essential oil of Ageratum conyzoides L. shows the presence of 12 compounds when analyzed by gas chromatography-mass spectrometry. The growth and aflatoxin production of the toxigenic strain Aspergillus parasiticus was completely inhibited by essential oil. All the studied concentrations of the oil demonstrate a reduction in mycelia growth and decreased production of different aflatoxins in fungi, as revealed by liquid chomatographic-tandem mass spectrometric analysis. Volatiles from macerated green leaf tissue of A. conyzoides were also effective against A. parasiticus. The strongest antibacterial activity was observed against the bacteria Staphylococcus aureus and Bacillus subtilis in a disk diffusion bioassay. Essential oil and methanol extract of A. conyzoides L. were assayed for their antioxidant activity. Methanol extract showed the highest antioxidant activity in FRAP and DPPH assay, whereas essential oil showed greater lipid peroxidation inhibition than methanol extract.

The plant's ethno-medicinal importance, antioxidant potential, inhibitory activity against the Aspergillus group of fungi and production of aflatoxins may add a new dimension to its usefulness in the protection of stored product.