Abstract
BackgroundStrychnos spinosa Lam. is a deciduous tree used in traditional medicine to treat infectious diseases. This study is designed to determine the antimicrobial, antioxidant and cytotoxic activities of extracts and fractions from leaves of S. spinosa.MethodsExtracts were obtained by maceration with acetone, methanol and dichloromethane/methanol (1/1) while fractions were prepared by liquid-liquid fractionation of the acetone extract. A broth serial microdilution method with tetrazolium violet as growth indicator was used to determine the minimum inhibitory concentration (MIC) against fungi, Gram-positive and Gram-negative bacteria. The antioxidant activity was determined using free-radical-scavenging assays, and the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay was used to determine cytotoxicity.ResultsFour extracts and five fractions had good to weak antimicrobial activity with MICs ranging from 0.04 to >1.25 mg/ml against both fungi and bacteria. The chloroform and ethyl acetate fractions had an MIC of 0.08 mg/ml against Aspergillus fumigatus. The n-butanol fraction had an MIC of 0.04 mg/ml against Cryptococcus neoformans. The hexane and chloroform fractions had an MIC of 0.08 mg/ml against Staphylococcus aureus. The antioxidant activities were much lower than that of the positive controls. Except for the alkaloid extract, all the extracts and fractions had free-radical-scavenging activity (IC50 ranging from 33.66 to 314.30 μg/ml). The cytotoxicity on Vero cells was reasonable to low with LC50 values ranging between 30.56 and 689.39 μg/ml.ConclusionThe acetone extract and the chloroform fraction had the highest antibacterial activity. By solvent-solvent fractionation it was possible to increase the activity against A. fumigatus and to decrease the cytotoxicity leading to a potentially useful product to protect animals against aspergillosis. Our results therefore support the use of S. spinosa leaves in traditional medicine to treat infectious diseases.
Highlights
Strychnos spinosa Lam. is a deciduous tree used in traditional medicine to treat infectious diseases
Extraction yield Dried powdered leaves of Strychnos spinosa were extracted with acetone, methanol, mixture (v/v) of dichloromethane/ methanol (1/1) and alkaloids extraction procedure to afford extracts (AcetE, MetE, DcmMetE and AlkE) with yields of 3.7, 11.9, 11.0, and 0.28%, respectively
Antimicrobial activities Antimicrobial of leaf extracts and fractions of S. spinosa were determined against four fungi and four bacteria and the results are given as minimum inhibitory concentrations (MIC) and total activity in Tables 1 and 2
Summary
Strychnos spinosa Lam. is a deciduous tree used in traditional medicine to treat infectious diseases. The genus Strychnos is a member of the Loganiaceae family comprising about 200 species Plant species of this genus have been used in folk medicine and in arrow and dart poisons in many parts of the world [1]. The fruit is generally considered by botanical collectors to be edible, but there are poison-makers who express a contrary opinion and consider the unripe fruit poisonous [2] It is widely spread in Africa from Senegal through tropical Africa to South Africa. The plant species is used in traditional medicine for treating snakebite, ulcers, wounds, headache, gastric and intestinal problems, venereal diseases, leprosy, diarrhea, and fever [2]. The antioxidant activity of the fruit extract of the same species was determined [10]. Several secondary metabolites including triterpenoids, sterols and essential oils [6,7] secoiridoids [11,12], alkaloids [13], and monoterpenes [14] have been indicated or isolated from Strychnos spinosa
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