Fractionation and bioassay-guided isolation of Loganin from the bark of Breonia perrieri Homolle, an endemic Rubiaceae from Madagascar

For the valorization of endemic plants of Madagascar’s flora, the study of plant Breonia perrieri (Rubiaceae) was performed. This study aimed to assess the potential antioxidant and antimicrobial activities from the bark of Breonia perrieri. The methanolic crude extract, the fractions resulting from the fractionation of the methanolic extract and the isolated compound from the active extract were tested. The antimicrobial activities were evaluated by disc diffusion method and microdilution technic and the potential antioxidant by the method of DPPH assay. Streptococcus pneumonia is the most sensitive bacterium tested with crude methanolic extract and soluble ethyl acetat (IZD = 11mm, MIC = 250 µg/mL). Soluble ethyl acetat showed the most powerful extract in scavenging ability on DPPH free radicals (IC50 = 5.43 ± 0.15µg/mL). The bioassay-guided of the ethyl acetate extract resulted in the isolation of iridoid glycoside namely Loganin. Its structure was established by spectroscopic methods. This compound exhibited strong DPPH scavenging activity with IC50 value of 1.50 µg/mL and showed antibacterial activity against Streptococcus pneumonia (IZD = 10 ± 0.5 mm). This is the first work of chemical and biological studies on B. perrieri.