A New Antimicrobial Phenylpropanol from the Leaves of Tabernaemontana inconspicua Stapf. (Apocynaceae) Inhibits Pathogenic Gram-Negative Bacteria

A chemical investigation of the leaves of Stapf. led to the isolation of a new phenylpropanol derivative, namely irisdichototin G ( ), together with nine known compounds, including one polyol derivative, dambonitol ( ); three alkaloids, 10-hydroxycoronaridine ( ), voacristine ( ) and vobasine ( ); two triterpenes lupeol ( ), betulinic acid ( ) and three sterols, sitosterol ( ), sitosterol-3-O-β-D-glucopyranoside ( ) and stigmasterol ( ). The structure of the new compound, as well as those of the known ones, was established by means of spectroscopic methods: NMR analysis ( and C NMR, 1H-1H-COSY, HSQC, HMBC and NOESY), high-resolution mass spectrometry (HR-ESI-MS) and comparisons with previously reported data. Among the known compounds, compound was firstly reported from the family Apocynaceae. Compounds - were tested for their antimicrobial effects against three Gram-negative organisms associated with human wound and systemic infections, namely 9435337A, 17102005 and 2137659B. Compounds , , and showed significant antimicrobial effects with minimum inhibitory concentrations (MIC) of 62.5 μg/mL, 62.5 μg/mL and 7.81 μg/mL, respectively, against , whereas compounds and showed significant antimicrobial effects, with a MIC value of 31.25 μg/mL against . In addition, compound showed significant antimicrobial activity, with a MIC value of 31.25 μg/mL against .