Characterization and Isolation of Piperamides from Piper nigrum Cultivated in Costa Rica

The piperamides profile of Piper nigrum cultivated in Costa Rica was studied using ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight high-resolution mass spectrometry (UPLC-ESI-QTOF-HRMS) on enriched-piperamides extracts. A total of 31 different piperamides were identified, 24 of them with a methylenedioxyphenyl moiety, including piperine and nine other compounds with the characteristic piperidine ring, as well as guineensine, retrofractamide B, and eight other piperamides with an N-isobutyl group. In addition, piperyline and two other compounds with a pyrrolidine ring, as well as piperflaviflorine B, holding a N-2-methylbutyl chain, were characterized. In turn, pellitorine and six other piperamides exhibiting a long olefinic chain instead of the methylenedioxyphenyl group were also tentatively identified. In addition, quantification was performed using UPLC coupled with a diode array detector (UPLC-DAD), with 15 piperamides being quantified, including piperine, piperyline, piperanine, and piperloguminine with values within the range of previous reports, while results obtained for guineensine (276.5–421.0 mg/100 g dry material) and pellitorine (414.4–725.0 mg/100 g dry material) were higher than those reported in the literature. Additionally, preparative and semi-preparative high-performance liquid chromatography (HPLC) separations allowed to isolate, besides piperine, four other piperamides, which were identified through HRMS, ¹H and ¹³C nuclear magnetic resonance (NMR). These included retrofractamide B, guineensine, pellitorine, and (2E,4E,12Z)-N-isobutyl-octadeca-2,4,12-trienamide, with yields of 134.0 mg/100 g dry material, 209.7 mg/100 g dry material, 361.8 mg/100 g dry material and 467.0 mg/100 g dry material, respectively, with all these values higher than those reported in previous studies in the literature. The findings constitute the first report of such a number and diversity of compounds in P. nigrum cultivated in Costa Rica.