M.M. Suleiman

Can MTT be used to quantify the antioxidant activity of plant extracts

Antioxidant properties of three different medicinal plant extracts from northern Nigeria were evaluated using the traditional qualitative 2,2, diphenyl-picrylhydrazyl (DPPH) method and a new 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) microdilution method described here. The results were in agreement. It is a simple, rapid and inexpensive method compared with many other methods for determining quantitative antioxidant activity of plant extracts.

Antifungal and antibacterial activities of different extracts of Harungana madagascariensis stem bark

The antifungal and antibacterial effects of the stem bark extracts of Harungana madagascariensis Lam. ex Poir. (Clusiaceae) were examined against nine microbial pathogens causing infections in both man and animals. Hexane (H), dichloromethane (D), chloroform (C), ethyl acetate (E), acetone (A), methanol (M), and water (W) extracts were tested in vitro through bioautography and minimum inhibitory concentrations (MIC) determination using the serial micro-dilution assays. Bioautographic results revealed the presence of eight different spots. Extract A exhibited the lowest MIC of 0.04 mg/mL against Microsporum canis, while water extract (W) and methanol (M) showed the highest MIC of 2.5 mg/mL against at least one of the tested fungi when compared to amphotericin B with 0.0625–1 g/mL. Sporotrichum schenckii was the most susceptible fungal pathogen with average MIC of 0.06 mg/mL, while the acetone extract (A) was the most active against three fungal organisms when compared with other extracts. Similarly, extracts D, C, E and A exhibited very high activity with low MIC values of 0.156–0.62 mg/mL, while M and W gave the highest values of 0.31–2.5 mg/mL on bacterial pathogens as compared to gentamicin (0.02–0.62 8 g/mL). The dichloromethane extract is the most active against bacteria with average MIC of 0.19 mg/mL, while Staphylococcus aureus is the most sensitive organism; that shows susceptibility at an average MIC of 0.34 mg/mL. These results provide promising information for the potential use of the crude extracts from the stem-bark of H. madagascariensis in the treatment of bacterial and fungal infections similar to what was obtained in the leaves.

A controlled study to determine the efficacy of Loxostylis alata (Anacardiaceae) in the treatment of aspergillus in a chicken (Gallus domesticus) model in comparison to ketoconazole

BackgroundThe poultry industry due to intensive methods of farming is burdened with losses from numerous infectious agents, of which one is the fungus Aspergillus fumigatus. In a preliminary study, the extracts of Loxostylis alata A. Spreng, ex Rchb. showed good activity in vitro against A. fumigatus with a minimum inhibitory concentration of 0.07 mg/ml. For this study crude, a crude acetone extract of L. alata leaves was evaluated for its acute toxicity in a healthy chicken model and for efficacy in an infectious model of aspergillosis (A. fumigatus).ResultsAt a dose of 300 mg/kg, the extract induced some toxicity characterised by decreased feed intake and weight loss. Consequently, 100 and 200 mg/kg were used to ascertain efficacy in the infectious model. The plant extract significantly reduced clinical disease in comparison to the control in a dose dependant manner. The extract was as effective as the positive control ketoconazole dosed at 60 mg/kg.ConclusionsThe results indicate that a crude extract of L. alata leaves has potential as an antifungal agent to protect poultry against avian aspergillosis.

Evaluation of selected South African plant species for antioxidant, antiplatelet, and cytotoxic activity

The antioxidant, antiplatelet, and cytoxoxic effects of seven South African plant extracts, namely, Combretum vendae A.E. van Wyk (Combretaceae), Commiphora harveyi (Engl.) Engl. (Burseraceae), Khaya anthotheca (Welm.) C.DC (Meliaceae), Kirkia wilmsii Engl. (Kirkiaceae), Loxostylis alata A. Spreng. ex Rchb. (Anacardiaceae), Ochna natalitia (Meisn.) Walp. (Ochnaceae), and Protorhus longifolia (Bernh. Ex C. Krauss) Engl. (Anacardiaceae), were evaluated using established in vitro assays. All the extracts showed comparably low toxicity except for the extract of C. harveyi that showed high hemagluttination assay titer value, which indicates toxicity. The extracts of P. longifolia, K. wilmsii, O. natalitia, L. alata, C. harveyi, and C. vendae exhibited antioxidant properties in the qualitative assay using DPPH. In the quantification of antioxidation using ABTS, only the extracts of P. longifolia, L. alata, and C. vendae showed antioxidant activity with respective TEAC values of 1.39, 1.94, and 2.08. Similarly, in the quantitative DPPH assay, L. alata (EC50, 3.58 ± 0.23 µg/mL) and K. wilmsii (EC50, 3.57 ± 0.41 µg/mL) did not differ significantly (p ≤ 0.05) from the control. K. anthotheca showed a higher EC50 (176.40 ± 26.56 µg/mL) value, and differed significantly (p ≤ 0.05) from all the other extracts and control. In addition, the extracts of C. vendae and C. harveyi showed significant (p ≤ 0.05) antiplatelet activity and did not differ from the control (aspirin) with EC50 of 0.06 ± 0.01 µg/mL and 0.19 ± 0.00 µg/mL, respectively. Lower EC50 values in the antioxidant and antiplatelet studies are indicative of superior activity of the plant extract against oxidation and platelet aggregation.

Biological Activities of Compounds Isolated from Loxostylis alata (Anacardiaceae) Leaf Extract

In a random screening of antimicrobial activity of tree leaves, Loxostylis alata (Spreng.) f. ex Reichb had shown activity against the pathogenic fungi; Cryptococcus neoformans. This stimulated further interest to investigate its antimicrobial activity. Extracts and compounds isolated from leaves of Loxostylis alata by bioassay-guided fractionation were evaluated for their in vitro antimicrobial, anti-inflammatory (Cyclooxygenase-1 and -2) activities and for their potential toxic effects using 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) and Salmonella typhimurium tester strains TA98 and TA100. Antimicrobial activity was evaluated using a serial dilution microplate assay. The bacterial strains used were Staphylococcus aureus (ATCC29213), Enterococcus faecalis (ATCC 29212), Pseudomonas aeruginosa (ATCC 27853) and Escherichia coli (ATCC 25922). While the fungal strains used were isolates of Cryptococcus neoformans, Sporothrix schenckii, Aspergillus fumigatus, Microsporum canis and Candida albicans. A bioassay guided fractionation of the crude extract yielded two antimicrobial compounds namely, Lupeol 1 and β-sitosterol 2. In addition β-sitosterol exhibited selective inhibition of COX-1 (IC 50 = 55.3 ± 2) None of the compounds isolated were toxic in the Salmonella typhimurium/microsome assay and MTT cytotoxicity test. The isolation of these two compounds is reported for the first time from Loxostylis alata.

NITRIC OXIDE INHIBITORY ACTIVITY OF STRYCHNOS SPINOSA (LOGANIACEAE) LEAF EXTRACTS AND FRACTIONS

Background: The study was aimed at determining the anti-inflammatory activity of fractions and extracts obtained from Strychnos spinosa leaves on a mediator of inflammation nitric oxide (NO). Materials and Methods: Leaves were extracted with acetone and separated into fractions with different polarities by solvent-solvent fractionation. The Griess assay was used to determine the nitric oxide (NO) inhibitory activity. Cellular toxicity was determined by “using the MTT reduction assay”. Results: With the exception of the ethyl acetate fraction which had an IC50 >750 μg/mL, all extracts and fractions had significant nitric oxide-inhibitory activity. The most active being the water fraction, chloroform fraction and the dichloromethane/methanol extracts with IC50 values of 88.43 μg/mL, 96.72 μg/mL and 115.62 μg/mL, respectively. The extracts and fractions had low cytotoxicity on macrophage U937 cell lines. Conclusion: Extracts and fractions of Strychnos spinosa leaves may be promising sources of natural anti-inflammatory agents. Findings obtained from this study showed that Strychnos spinosa leaves possess promising anti-inflammatory action and could be used in the treatment of inflammation-related conditions.