قلويدات الكينولينون الجديدة من الكستناء (كاستانيا كريناتا سيب) العسلNew Quinolinone Alkaloids from Chestnut (Castanea crenata Sieb) Honey

ABSTRACT: 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.
KEYWORDS: chestnut honey, Castanea crenata, alkaloid, quinolinone, kynurenic acid
■ INTRODUCTION
Honey is a natural sweet product produced by honey bees from
the nectar of flowers and has long been used as food and folk
remedy. Honey quality varies depending on the nectar source
of the plants such as chestnut, acacia, apple, cranberry,
sunflower, and vegetables.1 Many studies have reported that
honeys exert various biological effects including gastroprotective,
2 anti-inflammatory,3 antidiabetic,4 antimicrobial,5
anticancer,6 and antioxidative7 activities. Honey is composed
mainly of sugars (glucose and fructose) and various bioactive
constituents including minerals, vitamins, phenolics (flavonoids
and phenolic acids), and numerous volatile compounds.7,8
Additionally, several studies have reported that quinolinone
alkaloids are present in honeys with the highest concentrations
in chestnut honey apart from sugars.1,9−12 During the course of
investigations on chemical constituents of honeys, to understand
their quality and botanical origins, we isolated and
identified 16 compounds including two new and four known
quinolinone alkaloids from chestnut (Castanea crenata Sieb)
honey. In this study, we determined the structures of two new
quinolinone alkaloids from chestnut honey. In addition, we
identified a quinazolinone alkaloid, previously known as a
synthetic compound and now found as a natural product for
the first time.
■ MATERIALS AND METHODS
General Experimental Procedures. NMR spectra were obtained
with a unitINOVA 500 spectrometer (Varian, Walnut Creek, CA).
Pyridine-d5 and methanol-d4 (CD3OD) containing tetramethylsilane
were used as analytical solvents. All mass spectra were acquired on a
SYNAPT G2 hybrid (Waters, Cambridge, UK) equipped with an
electrospray ionization source (ESI−MS). Thin-layer chromatography
(TLC) was carried out by using silica gel TLC plates (silica gel 60
F254, 0.25 mm thickness) (Merck, Rahway, NJ) and developed using a
mixture of n-butanol/acet