Antiplasmodial activity of triterpenes isolated from the methanolic leaf extract of Combretum racemosum P. Beauv. (30th January 2020)

• Record Type: Journal Article
• Authors: Oluyemi, Wande M.; Samuel, Babatunde B.; Kaehlig, Hanspeter; Zehl, Martin; Parapini, Silvia; D'Alessandro, Sarah; Taramelli, Donatella; Krenn, Liselotte
• Is Part Of: Journal of ethnopharmacology. Volume 247(2019)
• Publication Date: 2020-01-30
• Subjects: Combretum racemosum -- Antiplasmodial activity -- Isolation -- Madecassic acid -- Triterpenes; Ethnopharmacology -- Periodicals; Pharmacognosy -- Periodicals; Herbs -- Periodicals; Herbs -- Periodicals; Pharmacognosy -- Periodicals; Pharmacognosie -- Périodiques; Herbes -- Périodiques; 615.1
• DOI: 10.1016/j.jep.2019.112203
• Languages: English
• ISSNs: 0378-8741

Abstract

Abstract: Ethnopharmacological relevance: Combretum racemosum showed activity in previous ethnopharmacological investigations of some Combretum species used in malaria treatment in parts of West Africa. Aim of the study: This study aimed at confirming the antimalarial potential of this plant by an activity-guided isolation of its active principles. Materials and methods: A crude methanolic leaf extract of Combretum racemosum and fractions thereof obtained by partition with chloroform and n-butanol were investigated for antiplasmodial activity against chloroquine-sensitive (D10) and chloroquine-resistant (W2) strains of Plasmodium falciparum . Repeated chromatographic separations were conducted on the chloroform fraction to isolate bioactive compounds for further tests on antiplasmodial activity. The characterization of the isolated substances was performed by applying NMR- and MS-techniques (ESI-MS, HR-ESIMS, 1D and 2D NMR). Results: The chloroform fraction (D10: IC50 = 33.8 ± 1.5 μg/mL and W2: IC50 = 27.8 ± 2.9 μg/mL) exhibited better antiplasmodial activity than the n-butanol fraction (D10: IC50 = 78.1 ± 7.3 μg/mL and W2: IC50 = 78 ± 15 μg/mL) as well as the methanolic raw extract (D10: IC50 = 64.2 ± 2.7 μg/mL and W2: IC50 = 65.8 ± 14.9 μg/mL). Thus, the focus of the phytochemical investigation was laid on the chloroform fraction, which led to the identification of four ursane-type (19α-hydroxyasiatic acid (1), 6β, 23-dihydroxytormentic acid (4), madecassic acid (8), nigaichigoside F1 (10) ) and four oleanane-type (arjungenin (2), combregenin (5), terminolic acid (7), arjunglucoside I (11) ) triterpenes, as well as abscisic acid (9) . Compounds 1 and 2, 4 and 5, 7 and 8 as well as 10 and 11 were isolated as isomeric mixtures in fractions CR-A, CR-C, CR-E and CR-H, respectively. All isolated compounds and mixtures exhibited moderate to low activity, with madecassic acid being most active (D10: IC50 = 28 ± 12 μg/mL and W2: IC50 = 17.2 ± 4.3 μg/mL). Conclusion: This paper reports for the first time antiplasmodial principles from C. racemosum and thereby gives reason to the traditional use of the plant. Graphical abstract: Image 1