Asperdichrome, an unusual dimer of tetrahydroxanthone through an ether bond, with protein tyrosine phosphatase 1B inhibitory activity, from the Okinawan freshwater Aspergillus sp TPU1343

A new unusual bis-tetrahydroxanthone connected through an ether bond, named asperdichrome (1), was isolated from a culture broth of Aspergillus sp. TPU1343 together with two known dimeric polyketides, secalonic acids D (2) and F (3). The fungus was isolated from a freshwater sample in Okinawa, Japan. The structure of 1 was elucidated on the basis of its spectroscopic data and comparisons were made with related compounds. Compounds 1 and 3 (heterodimers) inhibited the activity of protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 6.0 and 9.6 mu M, respectively. Compound 2 (homodimer) showed reduced activity against PTP1B (40% inhibition at 15.7 mu M). This is the first study on the inhibitory activities of tetrahydroxanthones against PTP1B. (C) 2015 Elsevier Ltd. All rights reserved.