Neobulgarones A similar to F from cultures of Neobulgaria pura, new inhibitors of appressorium formation of Magnaporthe grisea

Six new dimeric anthraquinone derivatives, neobulgarones A (3a), B (3b), C (4a), D (4b), E (5a) and F (5b), were isolated from the mycelia of the asco mycete Neobulgaria pura together with the monomeric carviolin (I) and 1-O-m ethylemodin (2). All new compounds inhibited the formation of appressoria i n germinating conidia of Magnaporthe grisea on inductive (hydrophobic) surf ace. The compounds exhibited moderate cytotoxic, but no antifungal, antibac terial, or phytotoxic activities.