The aqueous extract of the leaves of Odontonema strictum (OSM) is used in folk medicine for its antihypertensive properties, and it contains a wide range of secondary metabolites, mostly polyphenols such as verbascoside and isoverbascoside, which could play a major role in the preparation of silver nanoparticles. In this study, we aimed to prepare AgNPs for the first time using the OSM leaf extract (OSM-AgNPs) to investigate their free radical-scavenging potency against 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H₂O₂). Dynamic light scattering (DLS), UV/Vis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS) were used to characterize the OSM-AgNPs. With a size around 100 nm and a ζ-potential of −41.1 mV, OSM-AgNPs showed a good stability and a better colloidal property due to electrostatic repulsion and the dispersity. The strong absorption peak at 3 keV in the EDX spectra indicated that silver was the major constituent. Additionally, the existence of silver atoms was confirmed by the Ag 3d_5/2 peak around 367 eV in the XPS spectra. IC₅₀ values of 116 μg/mL and 4.4 μg/mL were obtained for the scavenging activities of DPPH and H₂O₂, respectively. The synthetic OSM-AgNPs can be further exploited as potential antioxidant agents.

The evaluation of the effects of the digestate produced by the reactor EB.06019.LHT-MWINDA on the pH of Kimwenza soil and the growth of Amaranthus cruentus was conducted during the dry season (June-July 2019). Two treatments were used for the experiment: NPK (T1) and digestate (T2). The untreated soil was taken as a negative control(T0). The results obtained show that the digestate has a more neutralizing effect on the acidity of the Kimwenza-mission soil than the mineral fertilizer: the pH increased from 4.40 ± 0.33 to 9.28 ± 0.45 for T2 versus 5.19 ± 0.59 to 7.71 ± 0.29 for T1. The plants treated with T2 gave leaves with relatively more weight (1.8 ± 0.5g) than those obtained with T1 (1.06 ± 0.87g). It was observed that plants treated with digestate were taller (10,4 ±1,1m) than those with NPK (9,45 ±1,13m). The average number of leaves obtained from plants was 7.06 ; 6.36 and 5.97 respectively for T2, T1 and T0. These results are an indication that the digestate produced by the reactor EB.06019.LHT-MWINDA could be used for the amendment of the acidic soil of Kimwenza-Mission and therefore contribute to reducing significantly the use of synthetic agro-chemicals, hence decreasing residual environmental and human health hazards.

The efficacy of the extracts of leaves of castor (Ricinus communis) on flea beetle (Nisotra gemella), ravaging sorrel (Hibiscus sabdariffa), was performed in the laboratory of Phytochemistry of the Faculty of Sciences (Loyola University of Congo). The insects were captured on the leaves of Hibiscus sabdariffa in the field using plastic jars. Toxicity tests were conducted in laboratory conditions in Petri dishes at a temperature of 28 ± 1°C. The results of the preliminary toxicity test of the total extracts showed a mortality of 100% for the petroleum ether extracts, 31.33% for the ethanolic extract, and 0% for the total aqueous extract, after 24 hours of exposure. The petroleum ether extracts was chosen for further investigations. Different concentrations of the total petroleum ether extract were applied on filter paper (1%: 0.53 μl / cm²; 0.1%: 0.05 μl / cm²; 0.05%: 0.03 μl / cm²) caused 100% mortality for the dose of 0.53 μl / cm² in the interval of 9 and 10 hours; 0.05 μl / cm² caused 100% mortality after 15 -16 hours. An interval of 19 to 20 hours was necessary to cause 100 % mortality using the concentration of 0.03 μl / cm². No mortality was recorded in control plates (petroleum ether). The same doses were used to evaluate the repellent effect. It was observed a low insect activity with an average rate of 39.5%. The thin layer chromatography enabled the identification of 10 spots (petroleum ether and ethyl acetate/ 5:1) and 8 spots (Petroleum ether and ethyl acetate/ 9:1).