Chemical and toxicological research on extracts from the leaves of Pittosporum senacia Poir. (Pittosporaceae), a medicinal plant endemic to Madagascar

A toxic activity has been observed in the extracts of Pittosporum senacia leaves, a Pittosporaceae from Madagascar. A bitter crude extract (CE) was obtained by hot aqueous extraction. A purification procedure from CE comprising ethanol precipitation, dialysis and fractionation with n-butanol yielded a partially purified extract (E3). The active ingredients, which had a bitter taste, were thermostable, precipitable by neutral lead acetate, absorbed by activated charcoal, and soluble in water, ethanol, and n-butanol. A phytochemical screening undertaken on E3 revealed the presence of phenolic compounds, unsaturated sterols, triterpenes and saponins. Mice injected with E3 at the lethal dose of 37.5 mg/kg by intraperitoneal (i.p.) route developed symptoms suggesting an attack of the central nervous system. The LD₅₀ was estimated between 26.05 and 27.41 mg/kg of body weight (b.w.). E3 provoked tissue lesions which were mainly characterized by hemorrhages in the heart, lungs and liver, and by vessel congestion in the brain, intestine and kidneys. In vitro, the active principles caused the lysis of sheep red blood cells. CE was also toxic to carp alvins (LC₅₀ = 27.54 μg/ml) and frog tadpoles (LC₅₀ = 28.11 μg/ml). CE inhibited the germination of diverse plant seeds. E3 and CE were active on Staphylococcus aureus with a Minimum Inhibitory Concentration (MIC) of 1.2 mg/ml and a Minimum Bactericidal Concentration (MBC) of 9.6 mg/ml for CE, and a MIC of 5.9 mg/ml and a MBC of 11.9 mg/ml for E3. CE exhibited a bacteriostatic activity (MBC/MIC= 8) and E3 a bactericidal activity (MBC/MIC= 2.01).