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The methanol crude extract of the bark of Psidium guajava (guava) previously displayed interesting cytotoxic effects on a panel of human cancer cell lines. In the present work, we plan to determine the toxicological effects of this guava botanical in Wistar rats. Acute oral toxicity of the extract was carried out by administration of a single dose of 5000 mg/kg body weight to female rats in 14 days. Subacute toxicity was conducted by oral administration of the extract at daily doses of 250 mg/kg, 500 mg/kg, and 1000 mg/kg body weight, respectively, while rats in the control group received no extract. After 28 days of treatment, animals were sacrificed for hematological and biochemical studies. In the acute toxicity study, no mortality or signs of toxicity were recorded; hence, the median lethal dose (LD50) of the Psidium guajava bark extract is greater than 5000 mg/kg body weight. For the subacute toxicity study, significant variations in body weight, relative weight of organs, and biochemical parameters were observed in the animals treated at different doses of the plant extract compared to control animals. Histopathological analyses showed minor liver inflammation in females treated at the highest dose (1000 mg/kg). These results suggest that intake of a single high dose of the Psidium guajava bark extract is nontoxic, but repeat administration could exhibit mild organ toxicity.

In order to contribute to the fight against infectious diseases, the in vitro antibacterial activity and the antibiotic-potentiating effects of Tristemma hirtum and five other Cameroonian edible plants have been evaluated against Gram-negative multidrug-resistant (MDR) phenotypes. The microdilution method was used to evaluate the bacterial susceptibility of the extracts and their combination to common antibiotics. The phytochemical screening of the extracts was carried out according to standard methods. Phytochemical analysis of the extracts revealed the presence of alkaloids, triterpenes, steroids, and polyphenols, including flavonoids in most of the tested extracts. The entire tested extracts showed moderate (512 μg/mL ≤ MIC ≤ 2048 μg/mL) to weak (MIC > 2048 μg/mL) antibacterial activities against the tested bacteria. Furthermore, extracts of leaf of Tristemma hirtum and pericarps of Raphia hookeri (at their MIC/2 and MIC/4) strongly potentiated the activities of all antibiotics used in the study, especially those of chloramphenicol (CHL), ciprofloxacin (CIP), kanamycin (KAN), and tetracycline (TET) against 70% (7/10) to 100% (10/10) of the tested MDR bacteria, with the modulating factors ranging from 2 to 128. The results of this study suggest that extracts from leaves of Tristemma hirtum and pericarps of Raphia hookeri can be sources of plant-derived products with antibiotic modifying activity.

Background: Bacterial infections, especially those caused by multidrug-resistant (MDR) Gram-negative bacteria, remain a global health concern. Previous studies have reported the antibacterial activities of the methanol extract of the leaves of Acacia polyacantha Willd. (Fabaceae) (APL) as well as some of its phytoconstituents. In this study, APL and its constituent, 3-O-[β-galactopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid (GGOA) were evaluated on growth kinetics, bacterial membrane, and H+-ATPase proton pumps. The acute toxicity of APL was also studied. Methods: The effects of APL and GGOA on bacterial growth kinetics and the bacterial membrane was determined using spectrophotometric methods. Their effects on the bacterial H+-ATPase proton pumps were evaluated through the acidification of the bacterial external environment using a pH-meter. The acute toxicity of APL was determined using the standard limit test method described by the Organization for Economic Cooperation and Development (OECD) code 425. Results: APL and GGOA modified the bacterial kinetics of Providencia stuartii ATCC29916 with emphasis on the latent phase. They blocked the proton pumps of this bacterium and destroy the bacterial membrane. The medium lethal dose (LD50) of APL was greater than 5000 mg/kg body weight (b.w.). Conclusion: The results of the present study provide important and complementary information on APL and GGOA as good antibacterial candidates for combating infections due to MDR Gram-negative bacteria. Keywords: 3-O-[β-galactopyranosyl-(1→4)-β-D-galactopyranosyl]-oleanolic acid; Acacia polyacantha; acute toxicity; Gram-negative bacteria; mode of action; multidrug resistance.