4. Discussion
The search for effective and safe anti-melanogenic agents derived
from natural products for both medicinal and cosmetic purposes
is of continuing interest. To our knowledge, this present
study gives the first evidence for the anti-melanogenic action of
pycnogenol via tyrosinase inhibition in conjunction with its broad
anti-oxidative effects using the B16 cell culture system.
In the experiments reported here, we examined the inhibitory
effects of pycnogenol on tyrosinase activity in B16 cells. To compare
the relative efficacy of pycnogenol against other tyrosinase
inhibitors, we measured the effects of pycnogenol along with the
well-known tyrosinase inhibitor, kojic acid (Lim, 1999). It was
found that pycnogenol was significantly stronger (IC50 = 11.2 lg/
ml) than kojic acid (IC50 = 49.1 lg/ml). We also measured the melanin
content of the pycnogenol-treated B16 cells, and found that
melanin biosynthesis was effectively suppressed in a dose-related
manner.
One other novel finding of our study of pycnogenol in B16 cells
is the enhancement of GSH levels, reduction of GSSG levels, and
up-regulation of the GSH/GSSG ratio (Fig. 4A–C. Although the
mechanism leading to this anti-oxidative reaction is not known
at present, it undoubtedly can contribute the biologic potency of
pycnogenol beyond other common antioxidants.
It is worthy to point out the cytotoxic effects of pycnogenol.
This question was checked out in the cell viability study. As shown
in Fig. 3, pycnogenol did not significantly affect cell viability at any
concentration tested compared with the untreated control