Rhizobialide: a new stearolactone produced by Mesorhizobium sp. CCNWGX022, a rhizobial endophyte from Glycyrrhiza uralensis.

The endophytic strain Mesorhizobium sp. CCNWGX022 was isolated from licorice (Glycyrrhiza uralensis Fisch.) grown in the arid and semi-arid regions of Northwest China. The new stearic acid derived gamma-lactone 1, named rhizobialide (= (5S)-4,5-dihydro-5-(8-oxotetradecyl)furan-2(3H)-one), was isolated from the petroleum-ether extract of the fermentation broth of this strain. The structure of 1 was elucidated on the basis of spectroscopic and mass-spectrometric analysis. This is the first report of this type of compound from rhizobia.