Bioguided Fractionation and Isolation of an Antiplasmodial Saponin from the Roots of Nauclea xanthoxylon (A.Chev.) Aubrév. (Rubiaceae)

• Published in: Chemistry & biodiversity 2023-04, Vol.20 (4), p.e202200271-n/a
• Main Authors: Nkouayeb Nangmou, Brice Maxime, Maza Djomkam, Hermine Laure, Bellier Tabekoueng, Georges, Tékapi Tsopgni, Willifred Dongmo, Mbahbou Bitchagno, Gabin Thierry, Mbock, Michel Arnaud, Kamkumo, Raceline Gounoue, Frese, Marcel, Ndjakou Lenta, Bruno, Ngouela, Silvère Augustin, Sewald, Nobert, Blaise Azebaze, Anatole Guy
• Format: Article
• Language: English
• Subjects: Acetic acid; Acids; Antimalarials - chemistry; Antimalarials - pharmacology; Antiprotozoal agents; Chloroquine; Chloroquine - pharmacology; Ethyl acetate; Fluorescence; Fractionation; Hexanes; Malaria; Natural products; Nauclea xanthoxylon; NMR; Nuclear magnetic resonance; Nucleic acids; Oleanolic Acid; Plant Extracts - chemistry; Plasmodium falciparum; Plasmodium falciparum - metabolism; Rubiaceae - chemistry; saponin; Saponins; Saponins - chemistry; Saponins - pharmacology; Ursolic Acid; Vector-borne diseases; xanthoxyloside
• ISSN: 1612-1872; 1612-1880
• DOI: 10.1002/cbdv.202200271

The root extract of Nauclea xanthoxylon (A.Chev.) Aubrév. displayed significant 50 % inhibition concentration (IC50s) of 0.57 and 1.26 μg/mL against chloroquine resistant and sensitive Plasmodium falciparum (Pf) Dd2 and 3D7 strains, respectively. Bio‐guided fractionation led to an ethyl acetate fraction with IC50s of 2.68 and 1.85 μg/mL and subsequently, to the new quinovic acid saponin named xanthoxyloside (1) with IC50s of 0.33 and 1.30 μM, respectively against the tested strains. Further compounds obtained from ethyl acetate and hexane fractions were the known clethric acid (2), ursolic acid (3), quafrinoic acid (4), quinovic acid (5), quinovic acid 3‐O‐β‐D‐fucopyranoside (6), oleanolic acid (7), oleanolic acid 3‐acetate (8), friedelin (9), β‐sitosterol (10a), stigmasterol (10b) and stigmasterol 3‐O‐β‐D‐glucopyranoside (11). Their structures were characterised with the aid of comprehensive spectroscopic methods (1 and 2D NMR, Mass). Bio‐assays were performed using nucleic acid gel stain (SYBR green I)‐based fluorescence assay with chloroquine as reference. Extracts and compounds exhibited good selectivity indices (SIs) of >10. Significant antiplasmodial activities measured for the crude extract, the ethyl acetate fraction and xanthoxyloside (1) from that fraction can justify the use of the root of N. xanthoxylon in ethnomedicine to treat malaria.