BACKGROUND : Strychnos 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.
METHODS : Extracts 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.
RESULTS : Four 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.
CONCLUSION : The 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.