and inhibiting elastase degradation of fibers.28 Isoflavones
also reduce UVB-induced MMP-1 expression, thus inhibiting
collagen degradation, but have not been shown to influence
collagen synthesis de novo.29
Soy protein has perhaps garnered the most attention for its
ability to lower cholesterol levels and its antiatherogenic effects
attributed to its antiproliferative and antioxidative activity.30,31
Genistein reduces lipid peroxidation, prevents antioxidant enzyme
depletion and decreases hydrogen peroxide formation.32
Irradiation of soybeans has been shown to increase the genistein
and daidzein content, which was correlated with increased
hydroxy radical scavenging activity.33 Genistein protects against
hydrogen peroxide induced DNA damage34 and also inhibits
UVB-induced apoptotic changes, including caspase 3 and P21.35
Green tea
Green tea is prepared from the plant Camellia sinensis and sold
as fresh or dried unfermented leaves. It contains high quantities
of monomeric catechins, the major ones being epicatechin (EC),
epigallocatechin (EGC), epicatechin gallate (ECG), and epigallocatechin
gallate (EGCG).36 Catechins are considered responsible
for the physiologic effects of green tea observed in vitro, with
EGCG recognized as the most abundant and biologically active
polyphenol at the cellular level.37,38 It is believed that tea polyphenols
exert their effects by binding to and activating specific
cellular membrane receptors. However, recent evidence has
revealed that catechins can be incorporated into the plasma
membrane, where they can translocate into the cytoplasm in
a manner akin to endocytosis and interact with different intracellular
molecular targets.39 Catechins exhibit broad antioxidant
activity via direct scavenging of free radicals, reduction of inflammatory
cytokines and downregulation of ROS producing
enzymes. In addition, tea polyphenols have been shown to
upregulate SOD, catalase and glutathione peroxidase and act
as metal chelators.40 However, there is evidence for significant
pro-oxidant activity as EGCG has been shown to induce apoptosis,
primarily in cancer cells, via the generation of hydrogen
peroxide and superoxide. This dichotomous spectrum of pro
and anti-oxidant properties is likely cell specific, but some have
suggested that the generation of low concentrations of ROS’s in
normal cells may induce cellular resistance to higher levels of
oxidative stress.37 Green tea is a UV damage protecting agent
inhibiting carcinogenic markers and UV-induced oxidative
stress, including suppression of AP-1, NF- ĸB, STAT-1 and the
MAPK cascade.4,41 In addition, it protects against PUVA induced
