RESUMO
The study of the conditions which affect the pharmacological activity of medicinal plants is the basis for the development of phytomedicine. This study aimed at identifying some optimal conditions for antibacterial activity of extracts of Harungana madagascariensis. The leaves, bark, and roots were harvested in Douala, Littoral Region of Cameroon, in August 2019 at three times of the day: early in the morning (6 a.m.), at midday (12 p.m.), and in the afternoon (6 p.m.). They were dried at room temperature and ground to give a fine powder. Each powder was macerated in methanol for 72 h and boiled in distilled water and palm wine. The obtained extracts were evaluated for their antibacterial activity by broth microdilution method on 31 clinical and 4 reference bacterial strains. The results show that the best extraction yield was obtained using the bark extracted from palm wine by decoction. The methanol bark extract was found to be more active than other solvents (8 and 512 µg/mL). In fact, the activity of the 6 a.m. extract was significant on 4 of the 35 strains tested (MIC< 100 µg/mL) and moderate on 27 of the 35 strains tested (100≤ MIC≤ 625 µg/mL). The activity of the noon extract was significant on 8 strains and moderate on 23 strains and, finally, the activity of the extract of 6 p.m. was significant on 9 strains and moderate on 25 strains. The extract harvested at 6 p.m. inhibited the growth of the 35 strains tested and revealed significant activity (MIC <100 µg/mL) on Staphylococcus aureus, Escherichia coli, Citrobacter freundii, Serratia marcescens, Salmonella enterica serovar typhi, and Yersinia enterocolitica, making this hour the best harvesting time. This study further confirms that the bark of H. madagascariensis is a potent antibacterial agent, being better still when harvested at 6 p.m. and extracted with methanol.
RESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Pteleopsis hylodendron is one of the most popular medicinal plants in Cameroon where it is used to treat measles, chickenpox, sexually transmitted diseases, female sterility, liver and kidney disorders as well as dropsy. To date there is no documented evidence corroborating its safety. This study thus aimed to determine the toxicity profile of the methanolic extract of Pteleopsis hylodendron. MATERIALS AND METHODS: The acute and sub-chronic toxicity of the methanolic extract of Pteleopsis hylodendron were investigated by employing established methods. The acute toxicity study was done by administering single doses (2-8 g/kg body weight) of plant extract to adult mice. For the sub chronic toxicity study, doses (85-680 mg/kg bw) of plant extract were administered daily to adult rats during 28 days after which the effect on organs, the hematological and biochemical parameters was assessed. RESULTS: In mice, single oral administrations of the methanolic extract of Pteleopsis hylodendron caused dose-dependent general behaviour adverse effects and mortality. The LD50 values were 3.00 and 3.60 g/kg bw for males and females respectively. In rats, daily single oral doses of the methanolic extract of Pteleopsis hylodendron provoked significant (p < 0.05) growth retardation in rats at all tested doses after 28 days of dosing. Haematological parameters showed a significant decrease in white blood cells count and significant increases red blood cells count; irrespective of the sex, all biochemical parameters studied, except triglycerides significantly (p < 0.001) increased with dose. However, a dose-dependent significant (p < 0.007) increase in HDL was observed only in male rats. Increases in liver enzymes (ALT and AST), proteins and creatinine levels correlate the observed histopathological damages (i.e. inflammation and vascular congestions) in the liver and kidneys. CONCLUSIONS: The overall results of this study indicate that the methanolic extract of Pteleopsis hylodendron stem bark possesses hepatotoxic and nephrotoxic effects at doses ≥ 85 mg/kg bw, suggesting that this plant should be used with caution.
