Chemical constituents of two Cameroonian medicinal plants: <i>Sida rhombifolia</i> L. and <i>Sida acuta</i> Burm. f. (Malvaceae) and their antiplasmodial activity
Blaise Cédric Kamdoum, Ingrid Konga Simo, Steven Collins Njonté Wouamba, Mariscal Brice Tchatat Tali, Bathélémy Ngameni, Ghislain W. Fotso, Pantaléon Ambassa, Fekam Boyom Fabrice, Bruno Ndjakou Lenta, Norbert Sewald, Bonaventure T. Ngadjui
Abstract
An extensive phytochemical investigation of the EtOH/H2O (7:3) extracts of Sida rhombifolia L. and Sida acuta Burm. f., yielded a previously undescribed ceramide named rhombifoliamide (1) and a xylitol dimer (2), naturally isolated here for the first time, as well as the thirteen known compounds viz, oleanolic acid (3), β-amyrin glucoside (4), ursolic acid (5), β-sitosterol glucoside (6), tiliroside (7), 1,6-dihydroxyxanthone (8), a mixture of stigmasterol (9) and β-sitosterol (10), cryptolepine (11), 20-Hydroxyecdysone (12), (E)-suberenol (13), thamnosmonin (14) and xanthyletin (15). Their structures were elucidated by the analyses of their spectroscopic and spectrometric data (1 D and 2 D NMR, and HRESI-MS) and by comparison with the previously reported data. The crude extracts, fractions, and some isolated compounds were tested against chloroquine-sensitive (3D7) and chloroquine-resistant (Dd2) Plasmodium falciparum strains. All the tested samples demonstrated moderate and/or significant activities against 3D7 (IC50 values: 0.18―20.11 µg/mL) and Dd2 (IC50 values: 0.74―63.09 µg/mL).