Essential oils (EOs) from Cymbopogon citratus (CC), Eucalyptus citriodora (EC), Eucalyptus camaldulensis (ED), and Citrus sinensis (CS) were obtained by hydrodistillation process. The EOs were evaluated in vitro for activity against Trypanosoma brucei brucei (Tbb) and Trypanosoma evansi (T. evansi). The EOs were found to possess antitrypanosomal activity in vitro in a dose-dependent pattern in a short period of time. The drop in number of parasite over time was achieved doses of 0.4 g/ml, 0.2 g/mL, and 0.1 g/mL for all the EOs. The concentration of 0.4 g/mL CC was more potent at 3 minutes and 2 minutes for Tbb and T. evansi, respectively. The GC-MS analysis of the EOs revealed presence of Cyclobutane (96.09%) in CS, 6-octenal (77.11%) in EC, Eucalyptol (75%) in ED, and Citral (38.32%) in CC among several other organic compounds. The results are discussed in relation to trypanosome chemotherapy.

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Bacteria resistance to antibiotics used for the treatment of infections and diseases is of global concern. Medicinal plants have been used as the primary sources of plants' active ingredients or lead compounds in drug development. The combination of various antimicrobial agents to obtain a synergistic effect is considered an ideal strategy for combating bacteria resistance. In this work, a constant repetitive synergy in all combinations was achieved by adding 0.3 mL of concentrated tetraoxosulphate (vi) acid, H2SO4 in a mixture of Calotropis procera extract separately with (a) 1 mg/mL Amoxicillin, (b) 1 mg/mL Ampicillin, (c) 100 µg/mL Azithromycin and (d) 100 µg/mL Ampicillin and were heated at 110 °C for 20 minutes. Higher zones of inhibitions were observed at 16.7 mm for Salmonella  spp, 16.4 mm for Shigella spp, 16.8 mm for Staphylococcus aureus, 21.3 mm for Escherichia coli and 22.4 mm for Streptococcus spp in situations where the antibiotics alone zone of inhibition was 0 mm at the same concentration of a, b, c, and d. These increase the regular probability model of obtaining synergism in plant extracts combination with antibiotics as shown by multiple literatures from 33% to 66% at antibiotic concentration of 100 µg/mL and 100% at antibiotic concentration of 1 mg/mL. The validation process using Piliostigma reticulatum extract shows that a volume of 0.1 mL of concentrated tetraoxosulphate (vi) acid in 2 mL of the mixture was enough to induce synergism to combat bacteria resistance. This work shows a cost-effective method where the antimicrobial activity of ineffective antibiotics can be enhanced and optimized using plant extracts. It can also be explored and applied in different ways to identify novel compounds, and isolate and purify their active principles for selectivity, efficacy, safety and their development as clinical trial candidates in antiviral and anticancer research to overcome enormous health challenges.

(1) Background: Malaria fever affects millions of people yearly in Africa and Asia’s tropical and subtropical areas. Because there is no effective vaccine, malaria prevention is solely dependent on avoiding human-vector interaction. (2) Aim: This study examines the interaction between the constituents of Vitex negundo essential oil and Anopheles gambiae Odorant Binding Proteins (OBP) as well as the compositional variation, repellent efficacy, and toxicity profile. (3) Methods: The oils were subjected to GC-MS and mosquito behavioral analysis. OBP–ligand interactions, Anopheles species authentication, and the toxicity profile were determined by molecular docking, PCR assay and in silico ADME/tox tool. Docking protocol validation was achieved by redocking the co-crystallized ligands into the protein binding pocket and root mean square deviation (RMSD) calculation. (4) Results: The oil yields and compositions are climate–soil dependent with ≈71.39% monoterpenes and ≈16.32% sesquiterpene. Optimal repellency is achieved at 15 min at ED50 0.08–0.48% v/v while the RMSD was estimated to be within 0.24–1.35 Å. Strong affinities were demonstrated by α-pinene (−6.4 kcal/mol), citronellal (−5.5 kcal/mol), linalool (−5.4 kcal/mol), and myrcene (−5.8 kcal/mol) for OBP1, OBP7, OBP4, and OBP; respectively. The hydrophobic interactions involve Leu17 (α-helix 1), Cys35 (α-helix 2), ALA52 (α-helix 3), Leu73, Leu76 (α-helix 4), Ala88, Met91, Lys93, Trp114 (α-helix 5), Phe123 (α-helix 6), and Leu124 (α-helix 7) receptors within the binding cavities, and may cause blocking of the olfactory receptors resulting in disorientation. (5) Conclusion: The ligand efficiency metrics, ADME/tox and repellency screening are within the threshold values; hence, α-pinene, linalool, and myrcene are safe and fit-to-use in the development of a green and novel repellent.