Ultraviolet-induced amides and casbene diterpenoids from rice leaves. (March 2016)

• Record Type: Journal Article
• Authors: Horie, Kiyotaka; Sakai, Kengo; Okugi, Misaki; Toshima, Hiroaki; Hasegawa, Morifumi
• Is Part Of: Phytochemistry letters. Volume 15(2016:Mar.)
• Page Start: 57
• Page End: 62
• Publication Date: 2016-03
• Subjects: EMS enhanced mass spectrometry -- EPI enhanced product ion -- SRM selective reaction monitoring -- PDA potato dextrose agar -- CUR curtain gas -- TEM temperature -- GS1 spray gas -- GS2 dry gas -- IS ion voltage -- DP declustering potential -- EP entrance potential -- CEP collision cell entrance potensial -- CE collision energy -- CAD collision gas; Ultraviolet irradiation -- Mass spectrometry -- Phytoalexin -- Rice; Botanical chemistry -- Periodicals; Chimie végétale -- Périodiques; 572.205
• DOI: 10.1016/j.phytol.2015.11.009
• Languages: English
• ISSNs: 1874-3900

Abstract

Graphical abstract: Highlights: N -Benzoyltyramine (1 ) was identified as a UV-inducible compound from rice leaves. Two new casbene diterpenes (2 and3 ) were isolated from UV-irradiated rice leaves. Compounds2 and3 may be biosynthetic intermediates of a casbene-type phytoalexin. Two known amides were recognized as phytoalexins in the rice– M . oryzae system. Abstract: To discover new phytoalexins, an 80% MeOH extract of UV-irradiated rice leaves was analyzed using LC–MS, resulting in the detection of three unidentified compounds. We isolated the compounds from the UV-irradiated rice leaves using chromatographic methods and identified the compounds as N -benzoyltyramine (1 ), and two casbene-type diterpenes, 5-dihydro- ent -10-oxodepresssin (2 ) and 5-deoxo- ent -10-oxodepressin (3 ), using spectroscopic methods. Additionally, we compared the accumulation levels of major UV-inducible compounds in response to Magnaporthe oryzae inoculation and the antifungal activities of the compounds against M . oryzae colony growth. Although1–3 showed negligible antifungal activity against M. oryzae, the compounds significantly accumulated in M. oryzae -inoculated rice leaves. Furthermore, we confirmed that N -benzoyltryptamine and N -cinnamoyltryptamine also accumulated after M. oryzae inoculation and have relatively high antifungal activity against M. oryzae to the same extent as phytocassanes. These results strongly support the hypothesis that the two amides are rice phytoalexins.