Pyrrole-type compounds from the flowers of Calotropis gigantea

Abstract

Calotropis gigantea, a large shrub, has been used in traditional folk medicines for the treatment of fever, cough, swellings, bronchitis or dyspepsia. Previous studies on C. gigantea reported that its main constituents, specifically cardenolides and pregnanes, had cytotoxic activity against A549 human lung, Hela human cervical cancer cell lines and K562 human chronic myelogenous leukemia. This paper presents the isolation of chemical constituents from the flowers of C. gigantea (Apocynaceae) in order to provide more information about its chemical compounds to the database on medical plants in Vietnam. By using silica gel column chromatography, preparative TLC and eluting with organic solvents of different polarity, results showed that five pyrroles, including pollenopyrroside B (1), epi-acortatarin A (2), shensongine A (3), 5-methoxymethyl-1H-pyrrole-2-carbaldehyde (4), 1-[2-(furan-2-yl)-2-oxoethyl]pyrrolidin-2-one (5), were isolated from the CHCl3 extract of the flowers of C. gigantea (Apocynaceae), collected at Binh Thuan province in March, 2020. Their chemical structures were elucidated by HR-MS and 1D, 2D NMR spectra analysis and comparison with published data. All compounds were the first reported from C. gigantea.