Bealem Aristide, Sakava Paul*, Lidia Favier, Didier Hauchard, Jean-Paul Guegan, Nyemb Jean Noël, Talla Emmanuel, Celine Henoumont, Sophie Laurent, Mbafor Tanyi Joseph
The aim of this work is to isolate, characterize, and evaluate the antioxidant activity as well as the phytotoxicity of crude extracts and compounds obtained from C. febrifuga. Nine compounds were isolated from leaves, stem bark and roots (methylene chloride/methanol:1/1) crude extracts after repeated silica gel column chromatography corresponding to shanzhiside methyl ester (1), D-mannitol (2), a mixture of two isomeric pentacyclic triterpenes: oleanolic acid (3a) and ursolic acid (3b), 11-methylixoside (4), 3β-urs-12, 20(30)-diene-27,28-dioic acid (5), quinovin glycoside C (6), 3-O-β-D-3-oxo-glucopyranosyl-ursa-12,20(30)-diene-27,28-dioic acid (7) and 3β-(-α-Lrhamnopyranosyloxy)-ursa-12,20(30)-diene-27,28-dioic acid (8). The compound chemical structures were established by studying their 1H and 13C NMR (1D and 2D) and Mass Spectrometry (MS) spectra. The antioxidant capacity of extracts were evaluated using a recently developed electrochemical method consisting in interacting with the superoxide anion radical (O2.-) generated in situ by reduction of air molecular oxygen (O2) in aprotic medium (anhydrous DMF). The antioxidant index is expressed as the amount of extract needed to consume 30% (AI30) of electrogenerated O2.-. The lower is the antioxidant index, the more active the substrate is against O2.-. The stem bark crude extract is the most active with an AI30 of 79.50mg/L while the leaves and root crude extracts showed a moderate activity against O2.- with AI30 of 303.70mg/L and 450.00mg/L respectively. The phytotoxicity study were carried out using a germination test on Lepidium sativum seeds in absence (0mg/L) and in presence of increasing concentrations (10, 100, 500, 1000mg/L) of crude extracts and the isolated compound (1). The following physiological parameters of the seedlings were evaluated 72 hours after the experimentation: germination percentage (G %), germination index (GI), vigor index (VI), relative root growth (RRG %). Root extracts are the most phytotoxic on seed germination with G% ranging from 66.66 to 100% and RRG% from 8.20 to 88.45% while the isolated compound (1) stimulated growth between 10-500mg/L but showed a moderate phytotoxic effect on seedlings above 500mg/L.