Etude biologique et phytochimique de Calobota saharae (Coss. & Dur.) Boatwr. & B.E. van Wyk

Abstract

The Saharan flora, found in sensitive ecosystems and particularly in the semi-desert areas of the northern Sahara, is very remarkable for its adaptation to a dry climate and a high salinity soil. The Present study of endemic species Calobota saharae focused on different aspects: plant ecology, morphology, phytochemical composition and biological activities. The morphological study is consistent with the description of Calobota saharae (Coss. & Dur.) Boatwr. & B.E.van Wyk, in the Crotalariae tribe and no longer in the Genistae tribe. At the level of the plant habitat, soil analysis has shown that the dune soil is poor in organic matter and nitrogen. The determination of the total nitrogen by the Kjeldahl method in the various organs of the plant is variable, however the rate is maximum in the seed (32% of proteins). The alkaloids are present in almost all parts of the plant (4.2%), but seem to focus in the green parts (branches and pericarp). In total 3 piperidine alkaloids were identified: ammodendrine, N-acétylhystrine and N-formylammodendrine. Flavonoid content varies between 0,2-2,6%, and total polyphenol content of 9.32% to 1.99% highest levels are observed for root samples collected in the month of August and the flowers collected in March. Purification by preparative HPLC made it possible to isolate 5-OMethoxy- 8-C- β -D-glucopyranosyl-genistein (5OMeC8CG). HPTLC bioautography and Mass Spectrometry Coupled Dereplication (HPTLC-MS) allowed for putative identification of phenolic compounds with antioxidant activity (DPPH radical scavenging). Main molecules identified as contributing to the antioxidant activity were identified as putative 3 ', 4', 5,7-tétrahydroxyisoflavones, the ficuisoflavone, 5-methoxy-4 ', 7-trihydroxy-8- gluco-pyranosyl-isoflavone and 4 5-Dihydroxy-7-methoxyisoflavone-4'-O- β -Dglucopyranoside. 5-O-methoxy-8-C-β-D-glucopyranosyl-genistein only contributes slightly to the antiradical activity of the extracts. Concerning the antibacterial activity, the strains Escherichia, Staphylococcus, Klebsiella, Serratia, have a sensitivity to alkaloidal extracts of Calobota saharae. The Pseudomonas strain, generally resistant to antibiotics has an intermediate sensitivity to the products test