Three yellow pigments were isolated from a mycelial extract of the entomopathogenic fungus Paecilomyces militaris. With the aid of spectroscopic means, one compound was identified as a new pyridone alkaloid, militarinone D (1). The two other metabolites were characterized as two novel 3-acyl tetramic acids, militarinones B (2) and C (3). In contrast to the structurally related pyridone militarinone A (4), compounds 1-3 showed only negliable neuritogenic activity in PC-12 cells, whereas militarinone D (1) exhibited cytotoxicity. On the basis of a co-occurrence of 3-acyl tetramic acids and biogenetically related pyridone alkaloids in P. militaris, a revised biosynthetic pathway for pyridone alkaloids is proposed.

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Two new yellow pigments, farinosones A (1) and B (2), were isolated from the mycelial extract of the entomogenous fungal strain Paecilomyces farinosus RCEF 0101, together with farinosone C (3), a new metabolite derived from an early step of pyridone alkaloid biosynthesis. The structures were determined by spectroscopic means, in particular by extensive NMR experiments. Compounds 1 and 3 induced neurite outgrowth in the PC-12 cell line at concentrations of 50 microM, while compound 2 was inactive. No cytotoxicity was observed for compounds 1-3 in PC-12 cells when tested at 50 microM concentration in the MTT assay.