Antiplasmodial and Cytotoxic Flavonoids from Pappea capensis (Eckl. & Zeyh.) Leaves

Abstract

Ethnobotanical surveys indicate that the Masai and Kikuyu in Kenya, the Venda in South Africa, and the Gumuz people of Ethiopia use Pappea capensis for the treatment of malaria. The present study aimed to investigate the phytochemical and antiplasmodial properties of the plant leaves. The bioactive compounds were isolated using chromatographic techniques. The structures were established using NMR, HRMS, and UV spectroscopy. Antiplasmodial activity of P. capensis leaf extract and isolated compounds against chloroquine-sensitive 3D7 P. falciparum was evaluated using the parasite lactate dehydrogenase assay. Cytotoxicity against HeLa (human cervix adenocarcinoma) cells was determined using the resazurin assay. The extract inhibited the viability of Plasmodium falciparum by more than 80% at 50 µg/mL, but it was also cytotoxic against HeLa cells at the same concentration. Chromatographic purification of the extract led to the isolation of four flavonoid glycosides and epicatechin. The compounds displayed a similar activity pattern with the extract against P. falciparum and HeLa cells. The results from this study suggest that the widespread use of P. capensis in traditional medicine for the treatment of malaria might have some merits. However, more selectivity studies are needed to determine whether the leaf extract is cytotoxic against noncancerous cells.

Phytochemical, Antiplasmodial, and Cytotoxic Investigation of Euclea natalensis A.DC. subsp. natalensis Leaves

“…The HMBC ( Figure S16 ) cross peak observed between the anomeric proton and δ C 136.2 (C‐3) confirmed the attachment of the rhamnosyl unit to position 3 of the quercetin nucleus. The identity of 4 was confirmed to be quercetin 3‐ O ‐α‐L‐rhamnoside ( 4 ) after comparing the spectral data and specific rotation with published literature data [23] …”

“…Moreover, both metabolites were also isolated as single compounds from other plants (in our research group); compound 3 from Pappea capensis Eckl. & Zeyh [23] . and compound 4 from Ozoroa obovata (Oliv.)…”

“…Thus, the structure of compound 3 was assigned as quercetin 3‐ O ‐α‐L‐arabinopyranoside ( Figure 1). [23,29] …”

“…Thus, the structure of compound 3 was assigned as quercetin 3-O-α-Larabinopyranoside (Figure 1). [23,29] Compound 4 was assigned a molecular formula of C 21 H 20 O 11 , based on a [MÀ H] À ion at m/z 448.0938 (calculated for C 21 H 19 O 11 447.0927) in the HR-ESI-(À )-MS (Figure S13). The NMR data (Figure S14-S17) of 4 revealed signals consistent with the presence of a quercetin derivative.…”

“…Despite the widespread use of E. natalensis for medicinal purposes, no previous attempt to investigate the phytochemical properties of the plant leaves has been reported. Therefore, in our search for antiplasmodial compounds from medicinal plants, [22–26] we investigated the leaf extract of E. natalensis for activity against 3D7 P. falciparum and cytotoxicity against Vero and HeLa cells.…”