Anti-Onchocerca and Anti-Caenorhabditis Activity of a Hydro-Alcoholic Extract from the Fruits of Acacia nilotica and Some Proanthocyanidin Derivatives

Abstract

Acacia nilotica fruits with high tannin content are used in the northern parts of Cameroon as anti-filarial remedies by traditional healers. In this study, the hydro-alcoholic fruit extract (crude extract (CE)) and, one of the main constituents in its most active fractions, (+)-catechin-3-O-gallate (CG), as well as four related proanthocyanidins, (−)-epicatechin-3-O-gallate (ECG), (+)-gallocatechin (GC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin-3-O-gallate (EGCG), were assessed for their potential in vitro anthelmintic properties against the free-living model organism Caenorhabditis elegans and against the cattle filarial parasite Onchocerca ochengi. Worms were incubated in the presence of different concentrations of fruit extract, fractions and pure compounds. The effects on mortality were monitored after 48 h. The plant extract and all of the pure tested compounds were active against O. ochengi (LC50 ranging from 1.2 to 11.5 µg/mL on males) and C. elegans (LC50 ranging from 33.8 to 350 µg/mL on wild type). While high LC50 were required for the effects of the compounds on C. elegans, very low LC50 were required against O. ochengi. Importantly, tests for acute oral toxicity (lowest dose: 10 mg/kg) in Wistar rats demonstrated that crude extract and pure compounds were non-toxic and safe to use. Additionally, the results of cytotoxicity tests with the Caco-2 cell line (CC50 ranging from 47.1 to 93.2 µg/mL) confirmed the absence of significant toxicity of the crude extract and pure compounds. These results are in good accordance with the use of A. nilotica against nematode infections by traditional healers, herdsmen and pastoralists in Cameroon.

An appraisal of natural products active against parasitic nematodes of animals

“…Other gallic acid analogues were isolated from the fruits of Acacia nilotica from the northern areas of Cameroon [54]. (+)-catechin-3-O-gallate, and four related proanthocyanidins: (+)-epicatechin-3-O-gallate, (+)-gallocatechin, (−)-epigallocatechin and (−)-epigallocatechin-3-O-gallate were all isolated and evaluated against C. elegans and O. ochengi .…”

Mining Sudanese Medicinal Plants for Antiprotozoal Agents

“…These peaks corresponded to catechin (Wulf et al, 2008) and epicatechin gallate (Salem et al, 2011), respectively. The occurrence of these compounds in V. nilotica has been reported (Khalid et al, 1989b;Dikti Vildina et al, 2017). Catechins were found to possess antiplasmodial activity by inhibiting both the ATPase and chaperone functions of the P. falciparum heat shock proteins (PfHsps) through direct binding to PfHsp70-1 and PfHsp70-z (Zininga et al, 2017).…”

Toxicity studies of Acacia nilotica (L.): A review of the published scientific literature

“…Several in vitro assays involving different types of mammalian cells have been used for high-throughput screening of toxicity effects of potential medicinal compounds as well as to identify potential safety (39,71). Certain chemical constituents of medicinal plants are found to have a hemolytic or anti-hemolytic effect on animal erythrocytes (44,72,73).…”

“…The methanol extracts of seed and husk showed low toxicity effects to the tested human lymphocyte at 100 ug/mL. Dikti Vildina et al used Caco-2 cell lines as model to evaluate the cytotoxicity effect of fruit extracts of A. nilotica (increasing concentrations up to 100 or 150 µg/mL) prior to in vivo toxicological studies (39). The results demonstrated that the viability of the tested human intestinal Caco-2 cells is inhibited by the crude extract of A. nilotica (mean CC 50 93.2 ± 1.1 µg/mL (µM)).…”