J.C. Chukwujekwu

Antimalarial sesquiterpene lactones from Distephanus angulifolius.

Combined use of bioassay-guided fractionation based on in vitro antiplasmodial assay and dereplication based on HPLC-PDA-MS-SPE-NMR led to isolation of (6S,7R,8S)-14-acetoxy-8-[2-hydroxymethylacrylat]-15-helianga-1(10),4,11(13)-trien-15-al-6,12-olid and (5R,6R,7R,8S,10S)-14-acetoxy-8-[2-hydroxymethylacrylat]-elema-1,3,11(13)-trien-15-al-6,12-olid, along with vernodalol, vernodalin, and 11,13beta-dihydroxyvernodalin from extract of Distephanus angulifolius. All compounds were identified by spectroscopic methods, including 1D and 2D homo- and heteronuclear NMR experiments. The isolated compounds showed IC(50) values in the range 1.6-3.8 microM and 2.1-4.9 microM against chloroquine sensitive D10 and chloroquine resistant W2 Plasmodium falciparum strains, respectively.

In vitro antimicrobial, anthelmintic and cyclooxygenase-inhibitory activities and phytochemical analysis of Leucosidea sericea

ETHNOPHARMACOLOGICAL RELEVANCE Leucosidea sericea is used as a vermifuge and in the treatment of ophthalmia by various tribes in southern African countries. AIM OF THE STUDY The study aimed at screening leaves and stems of Leucosidea sericea for pharmacological activity and validating the plants traditional use. A general phytochemical screening was also carried out. MATERIALS AND METHODS Petroleum ether (PE), dichloromethane (DCM), ethanol (EtOH) and water extracts of the plant parts were investigated for antimicrobial, anthelmintic and cyclooxygenase (COX) inhibitory activities. Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and Candida albicans were used for the antimicrobial evaluation. Caenorhabditis elegans was used for the anthelmintic assay using the microdilution technique. Cyclooxygenase-1 and -2 (COX-1 and -2) were used to evaluate the anti-inflammatory potential of the plant extracts. Phytochemical analysis for phenolic compounds, including gallotannins, condensed tannins and flavonoids was done using 50% methanol extracts of the leaves and stems employing spectrophotometric methods. RESULTS The leaf extracts exhibited broad spectrum antibacterial activity ranging from 0.025 to 6.25mg/ml. The most noteworthy minimum inhibitory concentration (MIC) of 0.025 mg/ml was exhibited by PE and DCM leaf extracts against Bacillus subtilis and Staphylococcus aureus, respectively. In the anthelmintic assay, the best minimum lethal concentration (MLC) value of 0.26 mg/ml was observed for the DCM and EtOH leaf extracts. Both leaf and stem organic solvent extracts exhibited high to moderate inhibition against COX-1 and -2 at a screening concentration of 250 microg/ml. At lower concentrations, the extracts displayed a dose-dependent inhibition, with the lowest IC(50) values of 0.06 microg/ml (COX-1) and 12.66 microg/ml (COX-2) exhibited by the PE extract of the leaves. Generally, the leaf extracts exhibited better pharmacological activities and contained higher amounts of phenolic compounds than the stem extracts. Alkaloids and saponins were only detected in the leaf and stem extracts, respectively. CONCLUSION The reported results support the local use of Leucosidea sericea against eye infections and as a vermifuge. The pharmacological activities exhibited by the leaf extracts are probably due to their higher phenolic levels.

Antibacterial Activity of Flavonoids from the Stem Bark of Erythrina caffra Thunb.

The antibacterial activity of the stem bark of Erythrina caffra Thunb. was investigated against different bacterial strains. The antibacterial activity was determined by a micro broth dilution assay. Antibacterial compounds were isolated and identified using a Bruker Avance III LPO NMR spectrometer. Four known flavonoids, abyssione‐V 4′‐O‐methyl ether, 6,8‐diprenylgenistein, alpinumisoflavone and burttinone, were isolated. All the compounds were active against both Gram‐negative and Gram‐positive bacteria. The minimum inhibitory concentration values obtained (MIC) ranged from 3.9 μg/mL to 125 μg/mL. This is the first report of antibacterial activity of burttinone and the isolation of these compounds from E. caffra. Copyright

Antibacterial, anti-inflammatory and antimalarial activities of some Nigerian medicinal plants

Petroleum ether, dichloromethane and 80% ethanol extracts of 15 plant species from Nigeria were screened for in vitro antibacterial, anti-inflammatory and antimalarial activities. Antibacterial activity was tested using agar diffusion and microtitre serial dilution tests. Most antibacterial activity was against Gram-positive bacteria, with Staphylococcus aureus being the most susceptible of the bacteria tested. The highest activity was found in both petroleum ether and dichloromethane extracts of Mallotus oppositifolius leaves, petroleum ether, dichloromethane and ethanolic extracts of Newbouldia laevis roots, and ethanolic extracts of Morinda lucida and Canthium subcordatum roots. Against the Gram-negative Escherichia coli, the highest activity was found in dichloromethane root extracts of Newbouldia laevis, ethanolic root extracts of Phyllanthus amarus, Mallotus oppositifolius and Canthium subcordatum. A total of 60 plant extracts was screened for antiplasmodial activity. A chloroquine sensitive strain of Plasmodium falciparum (D10) was used. In the assay, the parasite lactate dehydrogenase (pLDH) activity was used to measure parasite viability. Eleven extracts showed promising activity, with IC50 ranging from 2.5μg ml–1 to 13.8μg ml–1. Cyclooxygenase (COX-1 and COX-2) assays were used to test for antiinflammatory activity. All the plant species, except for two, showed anti-inflammatory activity, with activity mostly in petroleum ether and dichloromethane extracts.

Antimicrobial, antioxidant, mutagenic and antimutagenic activities of Distephanus angulifolius and Ormocarpum trichocarpum

ETHNOPHARMACOLOGICAL RELEVANCE The leaves of Distephanus angulifolius and Ormocarpum trichocarpum are used for treating stomach-related ailments in traditional medicine. AIMS OF THE STUDY The present study evaluated the antibacterial, antioxidant, mutagenic and antimutagenic properties of extracts obtained from the leaves of Distephanus angulifolius and Ormocarpum trichocarpum. MATERIALS AND METHODS The microtitre bioassay was used to determine the antibacterial activity against three Gram-positive and three Gram-negative bacteria. Antioxidant activity was determined using the free-radical scavenging and β-carotene-linoleic acid model assays. The safety and possible protective properties of the extracts were investigated using Ames test. RESULTS Dichloromethane fractions of both plants displayed a broad-spectrum antibacterial activity with minimum inhibitory concentrations ranging from 0.16 to 0.63 mg/ml. A dose-dependent antioxidant activity was recorded in both plant species. All the evaluated samples showed no mutagenic as well as weak or no antimutagenic properties in the absence of exogenous metabolic activation. CONCLUSION The results demonstrated the antibacterial and antioxidant activities of the leaves obtained from the two plant species. Furthermore, the data provides a rationale for the use of the plant species in treating stomach-related ailments in traditional medicine.

Anticholinesterase and mutagenic evaluation of in vitro-regenerated Agapanthus praecox grown ex vitro

Beyond establishing micropropagation protocols for medicinal plants, it is important that the efficacy and safety of propagated plants be ascertained for these plants to be accepted for use in traditional medicine. The use of propagated plants could alleviate/reduce over-exploitation of wild populations. The present study evaluated the anticholinesterase and mutagenic properties of 1-yr-old tissue culture-derived Agapanthus praecox grown ex vitro and naturally grown mother plants. The tissue culture-derived plants were regenerated using different plant growth regulators. A dose-dependent inhibition of acetylcholinesterase (AChE) enzyme was observed in all the tissue culture-derived and naturally grown mother plants. The leaf extract of tissue culture-derived plants regenerated with a combination of benzyladenine (BA) and thidiazuron (TDZ) demonstrated a significantly low AChE-inhibitory activity. Conversely, the root extract of plants regenerated with BA alone demonstrated the highest AChE-inhibition activity (IC50 = 0.20 mg/mL) when compared to extracts from other treatments and the naturally grown mother plants. None of the samples were found to be mutagenic in the absence of metabolic activation. The present study indicated that regenerated plants could be used as potent substitutes for naturally grown plants in traditional medicine. However, the choice of treatment used during micropropagation operation may significantly influence the therapeutic potential of regenerated plants, even after 1 yr of growth.

Antiplasmodial and Antibacterial Activity of Compounds Isolated from Ormocarpum trichocarpum

Using activity-guided fractionation based on in vitro antibacterial assays, five biflavonoids, among them two new ones, were isolated from the aerial parts of Ormocarpum trichocarpum. The isolated compounds showed MIC values in the range of 4.0 to 136.7 µM against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella pneumonia and IC50 values in the range of 4.30 to 94.32 µM against the chloroquine-sensitive D10 Plasmodium falciparum strain.

In vitro Antibacterial Activity of Combretum edwardsii, Combretum krausii, and Maytenus nemorosa and Their Synergistic Effects in Combination with Antibiotics

The study investigated the antibacterial activity of crude extracts of C. edwardsii, Combretum krausii, and Maytenus nemorosa as well as their interactions with selected antibiotics against drug resistant bacterial strains. Using the rapid p-iodonitrotetrazolium chloride colorimetric assay, minimum inhibitory concentration values of plant extracts and antibiotics were determined. The interactions of plant extracts and antibiotics were studied using a checkerboard method. The MICs of the plant extracts and antibiotics were in the range of 0.037–6.25 and 0.001–2.5 mg/ml, respectively. The plant fractions tested in the present study displayed varying levels of antibacterial activity depending on the bacterial strains. Generally, Staphylococcus aureus was the most susceptible of the three strains of bacteria while the other two beta-lactamase producing Gram-negative bacteria were the most resistant. The hexane leaf extract of M. nemorosa was the most active (MIC = 37 μg/ml) against S. aureus. Ethyl acetate leaf extract of C. krausii was the most active against Klebsiella pneumoniae and ethyl acetate leaf extract of C. edwardsii was the most active against Escherichia coli. Synergistic interactions were detected in 13% of the combinations against E. coli, 27% of the combinations against K. pneumoniae and 80% of the combinations against S. aureus. The few synergistic interactions observed in the present study suggest that the crude extracts of the leaves of M. nemorosa, C. edwardsii, and C. krausii could be potential sources of broad spectrum antibiotic resistance modifying compounds.

Alpha-glucosidase inhibitory and antiplasmodial properties of terpenoids from the leaves of Buddleja saligna Willd

Abstract In our continuing search for biologically active natural product(s) of plant origin, Buddleja saligna, a South African medicinal plant, was screened in line with its traditional use for antidiabetic (yeast alpha glucosidase inhibitory) and antiplasmodial (against a chloroquine sensitive strain of Plasmodium falciparum (NF54)) activities. The hexane fraction showed the most promising activity with regards to its antidiabetic (IC50 = 260 ± 0.112 µg/ml) and antiplasmodial (IC50 = 8.5 ± 1.6 µg/ml) activities. Using activity guided fractionation three known terpenoids (betulonic acid, betulone and spinasterol) were isolated from this species for the first time. The compounds displayed varying levels of biological activities (antidiabetic: 27.31 µg/ml ≥ IC50 ≥ 5.6 µg/ml; antiplasmodial: 14 µg/ml ≥ IC50 ≥ 2 µg/ml) with very minimal toxicity.

Phytochemical Characterization, Antibacterial, Acetylcholinesterase Inhibitory and Cytotoxic Properties of Cryptostephanus vansonii, an Endemic Amaryllid

Cryptostephanus vansonii I. Verd., an endemic Amaryllidaceae species from Zimbabwe, was evaluated for its acetylcholinesterase (AChE) inhibitory and cytotoxicity properties using Ellmans colorimetric method and the tetrazolium‐based colorimetric assay against Vero monkey kidney cells, respectively. The plant extracts were also evaluated for their antibacterial activity against five bacteria. Furthermore, phytochemical profiles of the extracts were determined using ultra‐high performance liquid chromatography coupled with tandem mass spectrometry analysis. A plant part‐dependent AChE inhibitory activity was observed, in the order, root > rhizome > basal leaf > leaf. Overall, C. vansonii extracts exhibited better antibacterial activity against Gram‐negative compared with Gram‐positive bacteria. Cytotoxic effects were not detected in Vero monkey kidney cell lines suggesting the possible absence of toxophores in C. vansonii extracts. Similar to the trend in biological activity, a distinct plant part‐dependent variation in hydroxybenzoates, hydroxycinnamates and flavonoids was observed in the plant extracts. In addition, 5‐hydroxymetylfurfural and eucomic acid were detected in the different plant parts of C. vansonii. The results of the present study provide valuable AChE inhibition activity, toxicological and phytochemical profiles of C. vansonii. Further studies on isolation of bioactive compounds and their subsequent evaluation in other pharmacological and toxicological model systems are required. Copyright