Lasiodipline G and other diketopiperazine metabolites produced by Lasiodiplodia chiangraiensis

Lasiodiplodia fungi are known to colonize plants as both pathogens and/or endophytes; hence, they can be exploited for their beneficial roles. Many compound classes from the genus have exhibited their potential biotechnological applications. Herein, we report two new metabolites 1 and 2 together with three known cyclo-(D-Ala-D-Trp) (3), indole-3-carboxylic acid (4) and a cyclic pentapeptide clavatustide B (5), isolated from the submerged cultures of a recently described species L. chiangraiensis. Chemical structures of the isolated compounds were determined by extensive NMR spectroscopic analyses together with HRESIMS. The absolute configurations of the new compounds were established based on comparing experimental and calculated time-dependent density functional theory circular dichroism (TDDFT-ECD) spectra. Compound 1 exhibited significant cytotoxic activities against an array of cell lines with IC(50) values of 2.9–12.6 μM, as well as moderate antibacterial effects.