A new β-carboline-type alkaloid from the flowers of Calotropis gigantea (L.) W.T.Aiton

• Published in: Natural product research Vol. 38; no. 17; pp. 3004 - 3012
• Main Authors: Dang, Phu H., Tran, Tu H., Le, Tho H., Do, Truong N. V., Nguyen, Hai X., Nguyen, Mai T. T., Nguyen, Nhan T.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 01.09.2024; Taylor & Francis Ltd
• Subjects: Alkaloids; Antioxidants; Apocynaceae; biosynthetic pathway; Calotropis gigantea; Calotropis gigantea (L.) W.T.Aiton; Chloroform; DPPH assay; Flowers; Free radicals; Imines; Nicotinic acid; NMR; Nuclear magnetic resonance; Phenols; Plant extracts; Scavenging; Thymine; β-carboline-type alkaloid; Apocynaceae; Calotropis gigantea (L.) W.T.Aiton; β-carboline-type alkaloid; DPPH assay; biosynthetic pathway
• ISSN: 1478-6419; 1478-6427; 1478-6427
• DOI: 10.1080/14786419.2023.2208259

In our antioxidant screening of some Vietnamese plant extracts, the CHCl 3 -soluble fraction from Calotropis gigantea (L.) W.T.Aiton flowers showed moderate DPPH free radical scavenging activity with an IC 50 value of 55.8 μg/mL. Thus, a further phytochemical study was carried out to obtain five alkaloids, including a new β-carboline-type alkaloid, caloside H (1). These known compounds were identified as 5-hydroxy-(2-methoxymethyl)pyridine (2), nicotinic acid (3), p-(acetylamino)phenol (4), and thymine (5). These structures were determined based on the NMR spectroscopic analysis. In antioxidant assay, caloside H at concentration of 100 μM showed DPPH radical scavenging capacity with a percentage of inhibition of 40.2%. In addition, a plausible biosynthetic pathway for the formation of caloside H was proposed based on the Schiff base formation and Mannich-like reaction.