ABSTRACT

This research studies the influence of substrate on the antioxidant activity of alcohol extracts of Paecilomyces hepiali. We used corn, rice, millet, and peas as substrates. Antioxidant activity was measured with the DPPH radical scavenging method. Concentrations of extracts (6.25, 3.12, 1.56, 0.78, and 0.39 mg/mL) were applied in all evaluations. Overall antioxidant activity was expressed as the concentration of substrate that decreased DPPH radical levels by 50% (IC₅₀^DPPH) for 7 methanol and 7 ethanol extracts. A comparison of IC₅₀^DPPH allowed us to conclude that the methanol extracts are more active in scavenging stable DPPH radicals than are the ethanol extracts. The substrate with antioxidant properties most suitable for cultivation of P. hepiali was rice supplemented with non-defatted soy flour. The extract most effective in scavenging stable radicals was the methanol extract of sample 4 (IC₅₀^DPPH = 2.33 mg/mL) cultivated on rice with nondefatted soy flour. The methanol extract of sample 7 cultivated on peas was less effective (IC₅₀^DPPH = 11.50 mg/mL). By crystallizing these extracts, we managed to obtain sufficient quantities of 6 samples in a solid state, for which infrared spectra were measured and confirmed the presence of amino acids in the extracts.