Attached
Plumbago indicaL., called “Rathnitul” in Sinhala
is a plant belongs to die family Plumbaginaceae, which
is widely used worldwide for its medicinal properties.
In Sri Lanka it is extensively used in traditional
m edicine and Ayurveda. The m ajor secondary
m etab o lites in the roots o f these plants are
naphthoquinones of which plumbagin (2-methyl-5-
hydroxy- 1,4-naphthoquinone) is predom inant.1
Previous studies claim that plumbagin exhibits highly
potent biological activities most importantly anticancer
activities.1 Although plumbagin has been shown to be
more toxic to cancer cells, it has also been shown to be
toxic to normal cells at high concentrations. Plumbagin,
in addition to possessing the common problems
associated with natural compounds such as inefficient
systemic delivery, poor bioavailability and reduced
oxidative stability, is also volatile,1 Therefore, design of
a “hybrid drug molecule” ofplumbaginby combining it
with appropriate metals and other ligands may provide
an opportunity to overcome these problems in its use for
cancer treatment.
Plumbagin was extracted from P. indica roots
using hexane.2 After recrystallization using hexane
plumbagin was obtained as orange coloured needles
(0.36 g, 0.72 %). In GC/MS studies, the gas
chromatogram showed a single peak and corresponding
mass spectrum with a molecular ion at m/z 188. IR and
UV spectroscopic results and melting point (76 78 °C)
were in accordance with published data and confirmed
that plumbagin has been successfully isolated.3 The
synthesis o f the Cu (D) metal complex was carried out
using plumbagin (PLN) and phenanthroline (PHEN) as
ligands in methanol.4 The erode obtained after the slow
evaporation of die reaction mixture was recrystallized
using methanol to yield the pure metal complex as dark
red crystals (0.254 g ,68.85%). In the IR spectrum of the
metal complex, 0 = 0 stretchings o f PLN were observed
at 1660 and 1621 a n '1 (C =0 stretching at 1621 cm*'has
shifted from 1641 cm'1 due to complexation) and C-H
stretchings of PHEN were observed at 848 and 785 cm'1
(shifted from 719 and 623 cm'1 due to coordination of
PHEN nitrogen atoms with the metal).5 UV absorption
studies also indicated die presence of both PLN and
PHEN ligands in the metal complex. Most importandy,
EI-MS (molecular ion at m/z 430) confirmed that
[Cu(PLN)(PHEN)jN03 has been synthesized (Figure
1).
In DNA binding studies using E-gel imager UV
transillumintor, the fluorescence produced by ethidium
bromide bound DNA gradually decreased in the
presence of increasing concentrations of the metal
complex and was not observed at and beyond 400 pM
of the metal complex (Fig. 2). Ethidium bromide is a
well-known DNA intercalating ligand. Our studies
indicate that the synthesized metal complex is able to
successfully intercalate to DNA replacing ethidium
bromide. These findings may lead to the possible use of
plumbagin as a “hybrid drug molecule” for the
treatment ofhuman cancers.
