Ricinus communis has been utilized traditionally as medicine to treat inflammatory related diseases including wounds, sores, and boils. The leaves of R. communis were sequentially extracted with n‐hexane, dichloromethane, acetone, and methanol using serial exhaustive extraction method. Antioxidant activity of all crude extracts was quantitatively measured against 2,2′‐azino‐bis (3‐ethylbenzothiazoline‐6‐sulphonic acid) free radical molecules using ABTS⁺ assay. Cytotoxic effect and anti‐inflammatory activity of R. communis leaves extracts were evaluated on Human Caucasian skin fibroblast and Raw 264.7 macrophage cell lines, respectively. Methanol extract had the highest percentage free radical (ABTS⁺) scavenging activity of 95% at 2.50 mg/mL, acetone 91%, dichloromethane 62%, and hexane the least (50%). Percentage scavenging activity of ABTS⁺ free radical molecules increases with increase in concentrations of the plant extracts. Hexane and dichloromethane extracts had more than 90% cell viability at 100 µg/mL after 24 and 48 hours of exposure. Methanol extract had LC₅₀ of 784 µg/mL after 24‐hour exposure, hexane had 629.3 µg/mL and dichloromethane 573.6 µg/mL, and 544.6 µg/mL was the lowest with acetone extract. The study present the first report on the scavenging activity of R. communis leaf extracts against ABTS⁺ radicals and cytotoxic effects on human Caucasian skin fibroblast cell lines.

Olea africana leaves are used by Bapedi people to treat different ailments. The use of these leaves is not validated, therefore the aim of this study is to validate antimicrobial properties of this plant. The ground leaves were extracted using solvents of varying polarity (hexane, chloroform, dichloromethane (DCM), ethyl acetate, acetone, ethanol, methanol, butanol and water). Thin layer chromatography (TLC) was used to analyse the chemical constituents of the extracts. The TLC plates were developed in three different solvent systems, namely, benzene/ethanol/ammonium solution (BEA), chloroform/ethyl acetate/formic acid (CEF) and ethyl acetate/methanol/water (EMW). The micro-dilution assay and bioautography method were used to evaluate the antibacterial activity of the extracts against Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus and the antifungal activity against Candida albicans and Cryptococcus neoformans. Methanol was the best extractant, yielding a larger amount of plant material whereas hexane yielded the least amount. In phytochemical analyses, more compounds were observed in BEA, followed by EMW and CEF. Qualitative 2, 2- diphenylpacryl-1-hydrazyl (DPPH) assay displayed that all the extracts had antioxidant activity. Antioxidant compounds could not be separated using BEA solvent system while with CEF and EMW enabled antioxidant compounds separation. The minimum inhibitory concentrations (MIC) values against test bacteria ranged between 0.16 and 2.50 mg/mL whereas against fungi, MIC ranged from 0.16 to 0.63 mg/mL. Bioautography results demonstrated that more than one compound was responsible for antimicrobial activity in the microdilution assay as the compounds were located at different Rf values. The results indicate that leaf extracts of Olea africana contain compounds with antioxidant, antibacterial and antifungal activities. Therefore, further studies are required to isolate the active compounds and perform other tests such as cytotoxicity. Olea africana may be a potential source of antimicrobial compounds.

Bidens pilosa and Dichrostachys cinerea extracts were investigated for the antibacterial properties against waterborne diarrhoeagenic bacteria. The plant materials were extracted using the direct and serial exhaustive methods using solvents of varying polarities, namely, hexane, dichloromethane, ethyl acetate, acetone and methanol. Qualitative phytochemical analysis and quantitative determination of total phenolic content of the leaf powders of the two plants were tested. The antioxidant activities of the plants were determined using the 2, 2-diphenyl-1-picrylhydrazyl method. The toxic effect of the extracts on C2C12 muscle cell line were assessed by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide method and the antibacterial activity was determined using the serial microbroth dilution. Methanol leaf extracts both plants had the highest yield in both direct and serial exhaustive extraction methods. Phytochemical profiling of the extracts displayed the presence of various secondary metabolites. The Benzene: ethanol: ammonia hydroxide solvent system showed a good resolution of chemical compounds in plant extracts from both plants. Most antioxidant compounds observed were developed in chloroform: ethyl acetate: formic acid and ethyl acetate: methanol: water solvent systems. All the bacterial species tested were sensitive to the effect of different extracts of both plant species, with E. coli being less sensitive to the effect of the extracts from D. cinerea. Following the simulated gastric fluid (SGF) treatment, a decrease in the antibacterial potency of the extracts was observed. No extract was toxic to the C2C12 muscle cell line. The presence of the secondary metabolites and nontoxic effect of the two plants tested may affirm the medicinal value of these leaf extracts. Our results suggest that B. pilosa and D. cinerea contain constituents with antioxidant and antimicrobial activities, which could be used in the treatment of diarrhoea in a case where untreated surface water is used.

Anti-Bacterial and Anti-Oxidant Activities of Leaf Extracts of Combretum vendee (Combretecacea) and the Isolation of an Anti-Bacterial Compound

The aim of the study was to scientifically evaluate the antimycobacterial activity of selected indigenous medicinal plants from the Limpopo Province used for the treatment of humans with symptoms ofMycobacterium tuberculosis. The leaves of five plant species (Apodytes dimidiata, Artemisia, Combretum hereroense, Lippia javanica, and Zanthoxylum capense) were collected from the Lowveld National Botanical Garden in Nelspruit, South Africa. The dried leaves were powdered and extracted using hexane, dichloromethane, acetone, and methanol. Antimycobacterial activity was evaluated using microdilution assay and bioautography andρ-iodonitrotetrazolium violet (INT) as indicator. Antioxidant activities were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH). Phytochemical content of extracts was further evaluated. The acetone extracts ofL. javanicadisplayed antioxidant activity on BEA chromatogram. T Acetone extracts ofA. afrahad MIC value of 0.39 mg/mL againstMycobacterium smegmatisATCC 1441. Acetone extracts ofC. hereroenseandL. javanicahad MIC value of 0.47 mg/mL. Four bands that inhibited the growth ofM. smegmatiswere observed atRfvalues of 0.12, 0.63, and 0.87 on BEA and 0.73 on EMW. The plant speciesA. dimidiata, A. afra, C. hereroense,andL. javanicain this study demonstrated their potential as sources of anti-TB drug leads.

The constant emergence of antibiotic resistant species and the adverse side effects of synthetic drugs are threatening the efficacy of the drugs that are currently in use. This study was aimed at investigating the possible antibacterial interactions, anti-inflammatory and cytotoxic effects of selected medicinal plants based on their traditional usage. The acetone extracts of four plant species were assessed independently and in combination for antibacterial activity using microdilution assay and the sum of the fractional inhibitory concentration (FIC) was calculated. The ability of Dombeya rotundifolia and Schkuhria pinnata extracts to inhibit the production of reactive oxygen species (ROS) in LPS induced RAW 264.7 macrophage cells was evaluated using Dichloro-dihydro-fluorescein diacetate (H2DCF-DA) assay to determine anti-inflammatory potential and the toxicity on African green monkey kidney (Vero) cells was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The antibacterial efficacies of the different combinations of Schkuhria pinnata (A), Commelina africana (B), Dombeya rotundifolia (C) and Elephantorrhiza elephantina (D) plants varied from combination to combination. Synergistic effects were only exhibited against P. aeruginosa, while the antagonistic effects were only observed against E. coli. Both S. pinnata and D. rotundifolia demonstrated anti-inflammatory potential by inhibiting the production of ROS in a dose dependant manner. The cytotoxicity of the plants (LC50 values) ranged from < 25.0 to 466.1 μg/mL. S pinnata extract was the most toxic with the lowest LC50 value of < 25.0 μg/mL. The synergistic interaction observed indicates that combinational therapy may improve biological activity. This report highlights the anti-inflammatory potential of S. pinnata and D. rotundifolia; which could be exploited in the search for anti-inflammatory agents. However, the cytotoxicity of S. pinnata highlights the importance of using this plant with caution.