Toxic properties of stem bark extracts of Myrica spathulata Mirb. (Myricaceae), a medicinal plant

Toxic activity has been demonstrated in extracts of Myrica spathulata Mirb. (or Morella spathulata) stem bark, a Myricaceae endemic to Madagascar. A purification process involving ethanol precipitation, dialysis and n-butanol fractionation yielded a partially purified extract (E3) from a hot aqueous crude extract (CE). The purification yield from CE was 29.87%. The active principles were thermostable, soluble in water, ethanol, but not in butanol, precipitable by neutral lead acetate and did not pass through the dialysis membrane (15,000 Da). Phytochemical screening of the partially purified extract (E3) revealed the presence of tannins, phenolic compounds, deoxyoses, leucoanthocyanins and unsaturated sterols. Mice administered intraperitoneally E3 at a lethal dose of 1087.8 mg/kg developed symptoms suggestive of damage to the nervous system and kidneys. The LD50 (24 h) was estimated at between 875.99 mg/kg and 877.8 mg/kg. In vitro, active ingredients lysed sheep red blood cells. CE was also toxic to tadpoles (LC₅₀ 24 h = 1.89 mg/ml). Fish Cyprius carpio were highly sensitive even at very low concentrations (0.12 μg/ml). CE had no effect on Culex quinquefasciatus mosquito larvae. It inhibited the germination of various seeds, and the growth of young seedlings of Oryza sativa (Monocotyledon) and Phaseolus vulgaris (Dicotyledon). Both CE and E3 were active against Staphylococcus aureus and Klebsiella pneumoniae.