Contribution à l’étude phytochimique et pharmacologique de trois plantes médicinales : Cissus populnea Guill. & Perr. (Vitaceae), Gardenia aqualla Stapf & Hucth (Rubiaceae) et Vitellaria paradoxa C. F. Gaertn (Sapotaceae

Abstract

The present work concerned the phytochemical and pharmacological investigation of Cissus populnea (Vitaceae), Gardenia aqualla (Rubiaceae) and Vitellaria paradoxa (Sapotaceae), three medicinal plants. The extracts of these species, were subjected to various chromatographic technique, affording several bioactive compounds, that were then characterized by modern spectroscopic methods, mass spectrometry and by comparison with related compounds described in the literature. The results reveal the isolation and identification of 29 compounds, including three new ones: an alkene namely pentapentacontene along with a fatty acid ester heptadecyl heptacosanoate from G. aqualla (Rubiaceae), and a cerebroside namely Vitellaroside, from V. paradoxa (Sapotaceae). The other known compounds belong to alkane (01),alcohols (05), chlorophylls (01), glycosides (02), phenolic compounds (08), steroid (01), sugars (02) and triterpenoids (06). D-Mannitol obtained from G. aqualla was derivatized to 1,2:5,6-di-O-isopropylidene-D-mannitol, while Catechin from V. paradoxa was used to synthesize a new coumarinoflavanol derivative through the Pechmann reaction. Some extracts and isolated compounds have been investigated for their DPPH antiradical scav enging activities, antimicrobial activities, Į-glucosidase and alkaline phosphatase inhibitory activities. The results of the DPPH antiradical scavenging activity showed that the crude MeOH extract of C. populnea rhizomes was the most active of all the extracts with an IC50 of 16.20 ±0.62 ȝg.mL-1. Antibacterial activities against E. coli, S. typhi and P. aeruginosa, as well asantifungals against C. albicans, C. krusei and C. parapsilosis, evaluated by the microdilution method, revealed the efficacy of most tested compounds with activities ranging from low to significant (8 MIC 128 ȝg/mL), depending on the compounds and microbial strains. Bacterial strains, were however more sensitive than fungi. The results of the Į-glucosidase inhibitory activity by the spectrophotometric method revealed that all the tested extracts were reservoirs of inhibitors of this enzyme, except for the MeOH extract of G. aqualla seeds. However, the highest activity, was recorded for the crude MeOH extract of C. populnearoots with an IC50 of 0.33 ± 0.04 ȝg.mL-1. Among all the tested compounds, 19Į, 23ȕ, 24Į-trihy droxyursolic acid was the most potent, with a significant activity (IC50 = 1.72 ± 0.1 ȝM; P < 0.05) greater than the one of Acarbose (IC50 = 234.6 ± 2.01 ȝM). Similarly, the results obtained from the alkaline phosphatase (AP) isozymes inhibitory activities (h-TNAP and h-IAP) using the CDP-Star luminescence method, showed more or less significant activities according to the tested compounds and the AP isoenzymes. The highest activity was however recorded for Bergenin against both isoenzymes but with a selectivity for h-TNAP.