Lipoxygenase inhibitory activity of the various plant extracts
was measured using lipoxygenase inhibition assay (Malterud and
Rydland, 2000). Linoleic acid was used as the substrate for the assay
and soybean lipoxygenase as enzyme. The enzyme solution was
pre-incubated for 5 min at 25 ◦C with various plant extracts that
served as test samples. The reaction was initiated by addition of
linoleic acid solution and borate buffer (0.2 M, pH 9.0). The reaction
mixture was incubated at 25 ◦C for 5 min. An ethanolic solution of
linoleic acid was added to stop the reaction and the absorbance was
measured at 234 nm. NDGA (Nordihydroguaiaretic acid) was used
as a positive control. The percentage inhibition of lipoxygenase
activity was calculated according to the formula: