Comparison of thyme, milk thistle and cape aloe essences on the growth of Aspergillus flavus and aflatoxin B1 production

Aspergillus flavus is the most important fungus for production of Aflatoxin B1 (AFB1). This toxin can be entered in the body through feed chain and ultimately leads to intoxications. The aim of this study was to investigate the effects of thyme (Thymus vulgaris L.), milk thistle (Silybum marianum L.) and cape aloe (Aloe vera) essences on the growth of A. flavus and AFB1 production. In this experimental study, concentrations of 0, 100, 200, 300 and 400 ppm of the studied plants essences were used in 4 replications. The AFB1 and major components of each essence were measured by Thin Layer Chromatography (TLC) and Gas Chromatography– mass Spectrometry (GC-MS) method. A rich medium (Yeast Extract Sucrose) was used for measuring the minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC). Carvacrol, silydianin, and glucomannan were the main constituents of the essential oil of thyme, milk thistle and cape aloe. The lowest yield of AFB1 production belonged to the concentration of 200 ppm in thyme essence (P=0.001). In contrast, the maximum yield of toxin was observed in the concentration of 100 ppm in cape aloe (P=0.013). However, MIC for thyme essence was 200 ppm and MFC of this essence was estimated 400 ppm. 300 and 400 ppm of thyme essences has the highest MIC and MFC on fungal colonies growth and AFB1 production. Thyme essence may be added to food to prevent fungal growth and aflatoxin production.