New Quinolinone Alkaloids from Chestnut (Castanea crenata Sieb) Honey

Two new quinolinone alkaloids and 13 known compounds were isolated from chestnut (Castanea crenata Sieb) honey. Two new compounds were determined to be 3-dihydro-spiro­[2­(1H),3′(1′H)-diquinoline]-3′,4,4′-trione (spirodiquinolinone) and 3-(2′-piperidine)-kynurenic acid. In addition, 2,3-dihydropyrrolo­[1,2-a]­quinazolin-5­(1H)-one was identified for the first time from nature. In addition, 2,3-dihydropyrrolo­[1,2-a]­quinazolin-5­(1H)-one was newly identified from chestnut honey, although this compound has been synthesized before. The structures were determined by the NMR and electrospray ionization–mass spectroscopy (ESI–MS). Three compounds were qualified and quantitated in chestnut honey by selective multiple reaction monitoring (MRM) detection of LC–ESI–MS using the isolated compounds as external standards.