Acinetobacter baumannii is a Gram‐negative pathogen which is widespread in nature. Although antibiotics such as carbapenems and polymyxins are used to treat A. baumannii infections, the emergence of multidrug‐resistant A. baumannii has greatly limited treatment options. Thus, A. baumannii infections are regarded as a great threat to global health. Previously, we successfully introduced the laeA gene into fungal strains in order to significantly increase the production of secondary metabolites, allowing us to create an original library (the Ō mura L aeA‐Introduced Fungal ( ŌLF ) library ) and discover novel biological activities. In this study, we aimed to discover antibacterial compounds against A. baumannii from the ŌLF library. Following the screening program, 3‐chlorogentisyl alcohol ( 1 ) was isolated from the Penicillium concentricum KTF‐0317 strain, which produced the compound in higher amounts than the corresponding wild‐type strain. Our investigations found that 1 demonstrated strong antibacterial activity even against quinolone ‐ resistant A. baumannii strain. However, difficulties were encountered in the purification of natural compound 1 . Therefore, synthetic samples were prepared via total synthesis and supplied for biological evaluation, enabling clarification of the structure–activity relationships. Our innovative approach revealed the overlooked biological activity of 1 and showed the prolificity and usefulness of the ŌLF library.
Honma et al. (Sun,) studied this question.