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Free radicals and reactive oxygen species are known to implicate in the
pathogenesis of various human diseases such as atherosclerosis, diabetes and
ischaemia-reperfusion injury. Numerous plant constituents have been shown to have
free radical scavenging or antioxidant activity. Mulberry (Marus alba) leaves have
been used to feed the silk worms and now they are also widely prepared as a beverage
for healthy, mulberry tea. It has been reported that the extract of mulberry leaves had
many pharmacological effects including antioxidant activity. However, most of the
information of antioxidant activity of mulberry leaves was evaluated in cell free
system. In order to obtain an additional important information for implementing the
mulberry leaves in therapeutic intervention, therefore, we examined the intracellular
antioxidative activity of mulberry leaves. An ethanolic extract of dried leaves of
M.alba var.Nakhonrajchasima 60 was used in all investigations. The effect of the extract
on superoxide produced within the rat peritoneal macrophages was tested by using
H2DCFDA (2',7'-dichlorodihydro fluorescein diacetate) probe. The production of
H2O2 was stimulated by phorbol-12-myristate-13- acetate. The fluorescence intensity
is proportional to the amount of H202 produced by cells. The extract of M. alba of
100 μg/ml significantly inhibited the production of peroxide (n=5, P<0.05). The free
radical scavenging and the reductive activities of the extract of M. alba were also
investigated. The free radical scavenging activity was determined by a method based
on the reduction of coloured stable free radical DPPH (1, 1-diphenyl-2-picrylhydrazyl).
The M. alba extract (1-300 μg/ml) scavenged the DPPH in the dose-dependent
manner with the IC50 of 20.1 μg/ml. The reductive activity was examined
by using the ferric reducing/antioxidant power (FRAP) assay. The extract was able to
reduce ferric complex to ferrous form in a dose-dependent mode. The extract at 10
μg/ml had the ferric reducing activity equivalent to vitamin C 1.2 μg/ml. It can be
concluded that the ethanolic extract of M. alba var.Nakhonrajchasima 60 has the free
radical scavenging and the reducing activities in cell free system together with the
intracellular antioxidant activity.
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