Phytochemical study of Juglans regia L. leaves

Juglans regia L. is a deciduous tree which most likely is native to Central Asia, Anatolia, northern parts of Iran and Himalaya. Nowadays it is cultivated nearly all over the world for walnut production [1]. Its aromatic odd-pinnate leaves are used in folk medicine for treatment of i.e. venous insufficiency, diarrhea, hypoglycemia, hypotension, skin tuberculosis, inflammations of mouth and marginal blepharitis [2 – 4]. The leaves contain phenolics like naphtoquinones, tannins, flavonoids, phenolcarboxylic acids and diarylheptanoids as well as monoterpenes, sesquiterpenes and megastigmanes [4 – 6]. In order to find potential new active secondary metabolites an EtOAc soluble fraction of a methanolic J. regia leaf extract was fractionated by various chromatographic techniques. Finally, ten hitherto unknown megastigmane glucoside derivatives (juglanionosides A-K, 1-10) and six tetralone glucoside derivatives (juglanosides J-O, 11-16) along with 24 already known compounds were isolated. 16 of them are reported to be isolated from the genus Juglans for the first time. Their structures were elucidated on basis of 1D and 2D NMR and mass spectrometric analysis.

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[1] Schaarschmidt, H. Die Walnussgewächse: Juglandaceae, 3 rd ed; Westarp Wissenschaften: Hohenwarsleben, 2006.

[2] Bruneton, J. Pharmacognosie, phytochimie, plantes médicinales, 2nd ed; Lavoisier: Paris, 1993.

[3] Wichtl, M.; Czygan, F.-C, Eds. Teedrogen und Phytopharmaka: Ein Handbuch für die Praxis auf wissenschaftlicher Grundlage, 4th ed; Wiss. Verl.-Ges: Stuttgart, 2002.

[4] Eisenman, S.; et al. Medicinal plants of Central Asia: Uzbekistan and Kyrgyzstan; Springer: New York, 2013.

[5] Bou Abdallah, I.; et al J Essent Oil Res 2016, 28, 545 – 550.

[6] Forino, M.; et al. J Funct Foods 2016, 26, 731 – 738.