The detailed chemical analysis of the methanol extract of Meripilus giganteus (Pers.) P. Karst. led to the isolation of two new cerebrosides, mericeramides A (1) and B (2) together with cerebroside B (3), ergosterol (4), 3β-hydroxyergosta-7,22-diene (5), cerevisterol (6), 3β-hydroxyergosta-6,8(14),22-triene (7), 3β-O-glucopyranosyl-5,8-epidioxyergosta-6,22-diene (8) and (11E,13E)-9,10-dihydroxy-11,13-octadecadienoic acid (9). The structures of the compounds were determined on the basis of NMR and MS spectroscopic analysis. Mericeramide A (1) is the first representative of halogenated natural cerebrosides. The isolated fungal metabolites 1-9 were evaluated for their antioxidant activity using the oxygen radical absorbance capacity (ORAC) assay. Compounds 2, 5 and 9 proved to possess considerable antioxidant effects, with 2.50 ± 0.29, 4.94 ± 0.37 and 4.27 ± 0.05 mmol TE/g values, respectively. The result obtained gives a notable addition to the chemical and bioactivity profile of M. giganteus, highlighting the possible contribution of this species to a versatile and balanced diet.
Keywords: Meripilaceae; Meripilus giganteus; ORAC assay; antioxidant; cerebroside; steroids.