Bacillinaphthin A: A New Naphthohydroquinone from the Endophyte Bacillus subtilis NPROOT3

The present study explores the endophyte associated with the halophyte Salicornia brachiata for uncovering new biologically important compounds. Thus, HPLC-PDA guided chemical investigation of the ethyl acetate extract of the Bacillus subtilis NPROOT3 led to the isolation of a new compound named bacillinaphthin A ( 1 ) along with previously known rubinaphthin A ( 2 ). The structure of 2 was determined by a comparison of HR-ESI-MS, ¹H and ¹³C nuclear magnetic resonances (NMR) with those of reported data, whereas the structure of new compound 1 was elucidated by interpretation of 1D- and 2D-NMR and MS data. Bacillinaphthin ( 1 ) and rubinaphthin ( 2 ) feature 1,4-dihydroxy-2-naphthoic acid derivatives which have been isolated herein for the first time from the genus Bacillus. Bacillinaphthin ( 1 ) is a new congener of 2 with an additional succinic acid side chain attached to the sugar moiety. Production of succinoglycan compounds was reported to regulate symbiosis, hence the isolation of 1 exhibits an example of chemical ecology between the halophyte and its endophyte. In silico tools were used to assess the bioactive potential of both isolated molecules.