Pityriasis versicolor is the most common skin mycosis in humans worldwide. Yeasts of the genus Malassezia, particularly M. furfur, a saprophyte occurring widely on human skin, are generally regarded as the causative agents. Pityriasis versicolor is often accompanied by a long-lasting depigmentation that persists even after successful antimycotic therapy. M. furfur is able to convert tryptophan into a variety of indole alkaloids, some of them showing biological properties that correlate well with certain clinical features of pityriasis versicolor. This suggests a possible role for these compounds in the depigmentation process. We now report that human melanocytes undergo apoptosis when exposed to the crude mixture of tryptophan metabolites from M. furfur. The active compound was identified as malassezin, previously isolated by us from the same source and characterized as an agonist of the aryl hydrocarbon (Ah) receptor. The compound could, therefore, contribute to the marked depigmentation observed during the course of pityriasis versicolor.

Eleven new indole alkaloids were isolated from cultures of the human pathogenic yeast Malassezia furfur after addition of L‐tryptophan as the sole N‐source: pityriacitrin B (2), the malassezindoles A (3) and B (4), malassezialactic acid (6), the malasseziazoles A (7), B (8), and C (9), pityriazole (10), malasseziacitrin (11), and malassezione (12), along with the known d‐indole‐3‐lactic acid (=(αR)‐α‐hydroxy‐1H‐indole‐3‐propanoic acid 5), and 2‐hydroxy‐1‐(1H‐indol‐3‐yl)ethanone (13). The structural elucidation of these compounds was performed by spectroscopic methods (MS as well as 1D‐ and 2D‐NMR). The biogenetic relationships (Scheme) and biological activities of the new metabolites are discussed.

Dedicated to Professor Rolf Huisgen on the occasion of his 85th birthdayEleven new indole alkaloids were isolated from cultures of the human pathogenic yeast Malassezia furfur after addition of l-tryptophan as the sole N-source: pityriacitrin B (2), the malassezindoles A (3) and B (4), malassezialactic acid (6), the malasseziazoles A (7), B (8), and C (9), pityriazole (10), malasseziacitrin (11), and malassezione (12), along with the known d-indole-3-lactic acid ( (aR)-a-hydroxy-1H-indole-3-propanoic acid 5), and 2-hydroxy-1-(1H-indol-3-yl)ethanone (13). The structural elucidation of these compounds was performed by spectroscopic methods (MS as well as 1D-and 2D-NMR). The biogenetic relationships (Scheme) and biological activities of the new metabolites are discussed.

Dedicated to Professor Timm Anke on the occasion of his 60th birthdayOccasionally the Yellow Parasol or Flower Pot Parasol (Leucocoprinus birnbaumii (Corda) Singer) appears in flowerpots and greenhouses, where it attracts attention because of its intense yellow color and delicate shape. It originated in the tropics and was distributed worldwide with plants and potting soil.[1] Until now, the chemical constituents of the fungus have remained unknown. Herein, we report the unusual structures of its yellow pigments, which we have named birnbaumin A and B.To isolate the pigments, the fruit bodies were extracted carefully with methanol. Subsequent separation of the extract by preparative reversed-phase HPLC yielded birnbaumins A and B, together with l-tryptophan. Although the two pigments have similar UV/Vis spectra, the major compound, birnbaumin B, exhibits a bathochromic shift of the absorption maximum from 322 (for birnbaumin A) to 356 nm (both in MeOH). Birnbaumin A shows a [M+H] + peak in the ESI mass spectrum at m/z 361. High-resolution measurements revealed the molecular formula C 16 H 20 N 6 O 4 . According to ESI MS, birnbaumin B differs from birnbaumin A by an additional oxygen atom.[2] ESI MS/MS spectra of the pigments display a fragmentation of the molecules into two characteristic parts. A fragment with a peak at m/z 200 (C 7 H 14 N 5 O 2 ) is common to both compounds, whereas the other fragment shows a peak at m/z 160 (C 9 H 6 NO 2 ) in the spectrum of birnbaumin A and at m/z 176 (C 9 H 6 NO 3 ) in that of birnbaumin B. The high content of Na + and K + ions detected by atom absorption spectroscopy of the samples suggests that the birnbaumins have the ability to complex metal ions.Further insight into the structure of the birnbaumins was provided by their NMR spectra. The 1 H NMR spectrum ([D 6 ]DMSO; DMSO = dimethyl sulfoxide) of birnbaumin A shows signals corresponding to a 1,2-substituted benzene ring, a single hydrogen atom on an aromatic ring (at d H = 7.98 ppm), and a ÀNHCH 2 CH 2 CH 2 CH 2 NHÀ unit. Additionally, at low field there is a sharp singlet at d H = 11.95 ppm and a broad signal at d H = 12.32 ppm, which we assign to OH protons. The 13 C NMR spectrum contains 16 signals, which correspond to four methylene and five aromatic methine groups, as well as seven quaternary carbon atoms (signals at d C = 109.8, 121.4, 134.1, 151.4, 156.7, 161.6, and 183.8 ppm). The HMBC spectra of birnbaumin A enabled the deduction of the partial structure shown in Scheme 1, whereby an a fragmentation between the two carbonyl groups would explain the generation of the key ions with m/z 160 and 200 in the mass spectra. According to the NMR spectra and HMBC experiments, birnbaumin B contains an additional hydroxy group on the indole ring system at the 7-position, which is in agreement with the production of the fragment ions with m/z 176 and 200.To confirm the substitution pattern, birnbaumin B was reduced with zinc in glacial acetic acid. The reductive loss of the N-hydroxy group causes a large shift of the 2-H...

Two strains of C. perftingens type A (FDI and S45) were grown in Thioglycolate medium adjusted to aws of 0.995, 0.975, or 0.965 by the addition of NaCl, KCl, or LiCl. Combinations of controlled and uncontrolled pHs (7.0, 6.5 and 6.0) and incubation tempera-' tures of 45"C, 37"C, or 30°C were observed at each a,. Maximal numbers of cells and shortest lag times occurred at a, of 0.995, 45°C and pH 7.0. No growth occurred at a, of 0.965. At 0.985, growth did not occur when KC1 was used as the solute and the temperature and pH were 30°C and 6.0, respectively. NaCl was less inhibiting than KCl. LiCl inhibited growth completely.