Abstract:
This study was conducted to determine the total phenolic content and antioxidant
activity of selected green vegetables. The effect of thermal treatment on antioxidant
activity and phenolic content were also studied. Brassica alboglabra (Kale), Amaranthus
oleracea (spinach), Brassica rapa var parachinensis (flowering white cabbage) and
Brassicajuncea (mustard green) were used in this study. Methanol was used as extracting
solvent. The oxidative activity of methanol were measured by using 2,2- diphenyl-2-
picrylhydrazyl (DPPH) assay method whereas, total phenolic compound (TPCs) was
measured by using Folin-Ciocalteu method. Among the samples tested, methanol extracts
of flowering white cabbage had a highest total phenolic content while the lowest was seen
in spinach's extracts for the fresh ones. It is interesting to note that there were significant
(p<0.05) difference between all samples tested. In Folin-Ciocalteu method, the samples of
blanching method was seen to have the highest while boiling had the lowest in total
phenolic content. In DPPH method, it is interesting to note that there were significant
(p<0.05) difference towards the different cooking methods for the methanol extracts of
kale. Among the samples tested, extracts of kale shown the highest antioxidant activity
during all cooking methods except for blanching method. There were no significant
difference in oxidative activity towards all different cooking method in extracts of
spinach and mustard green. In DPPH method, the fresh samples showed the highest while
boiling method was seen to have the lowest in antioxidant activity.
