Preliminary Studies on Lipoxygenase Inhibitory Activity of Selected Malaysian Medicinal Plants

A potential source for new lipoxygenase inhibitors is undoubtedly provided by the abundance of medicinal plants used in traditional medicine. As part of screening programme for biologically active plants, 20 extracts of different parts of 10 Malaysian medicinal plants belonging to four families were evaluated for their inhibitory activity on soybean 15-lipoxygenase (15-sLo). The leaves of Peronema canescens Jack. (Verbenaceae) were shown to be the most potent inhibitor with an IC₅₀ value of 25.64 ,g/ml. While the extracts of P. canescens stem and Stereospermum fibricatum DC. (Bignonaceae) leaves were found to possess profound inhibitory activity with IC50 values of 33.65 and 39.41 ,g/ml, respectively. The methanol extracts obtained from Stenolobium stans (L.) D. Don (Bignonaceae) leaves and stems, Piper ribesioides Wall. (Piperaceae) stems and S. fibricatum stems were moderately active with IC50 values ranging from 40 to 60 ,g/ml. While the remaining samples showed low lipoxygenase inhibitory activity at concentration of 100 ,g/ml.