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Revisiting Costa Rican Carapichea affinis (Rubiaceae: Palicoureeae): A source of bioactive dopamine-iridoid alkaloids

Kornpointner, Christoph, Berger, Andreas, Fischer, Isabella Maria, Popl, Louise, Groher, Christiane, Valant-Vetschera, Karin, Brecker, Lothar, Schinnerl, Johann
Phytochemistry letters 2018 v.26 pp. 164-169
Carapichea ipecacuanha, Spodoptera littoralis, bark, emetine, flavonoids, glucosides, insect pests, leaf extracts, leaves, mass spectrometry, nuclear magnetic resonance spectroscopy
Phytochemical investigations of methanolic extracts obtained from leaves and stem bark of Carapichea affinis (Rubiaceae: Palicoureeae), a poorly known relative of the famous vomiting root ipecac (C. ipecacuanha), led to the isolation and identification of two new and five known dopamine-iridoid alkaloids. All of them are structurally related to the famous emetic and anti-amoebic compound emetine. The known glucosides borucoside, cephaeline, 6-O-methyl-trans-cephaeloside, ipecoside and 6-O-methyl-ipecoside were isolated together with two novel alkaloids: 7-O-methyl-alangine and the cephaeloside derivative 3'''-O-demethyl-borucoside. All alkaloid structures were confirmed on basis of 1D- and 2D-NMR spectroscopy and mass spectrometry. Additionally, the flavonoid glycoside nicotiflorine was identified on basis of UV spectrum and retention time in the leaf extract. Feeding assays against the insect pest Spodoptera littoralis were carried out with alkaloid-rich aqueous phases of leaf and stem bark extracts.