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N. Ahmad et al. / Bioorg. Med. Chem. Lett. 19 (2009) 3521–3524
orientation. Hydroxy and methoxy groups in the 1,4- and 1,3-ori-
H
enntation at phenyl/cinnamoyle are mainly involved in the scav-
enging of coumarinolignoids (1-6). The ortho substitution with
electron donor methoxy group in 1,4-oriennted phenyl/cinnamoy-
le hydroxyl compounds slightly increase the scavenging activity.
This was observed in compounds 2 and 3. Based on these results,
a benzene ring where the hydroxyl radical is in 1,4-orienntation al-
low the oxygen atom to share a positive charge, thereby causing
stabilization through delocalization. Because of the electron donat-
ing effect of the methoxy group in 1,3-orienntation, it helps to sta-
bilize positive charge and this is taught to influence the scavenging
ability. The substitution radical of 1,2- or 1,4-orienntation gener-
ally donate an electron to the aromatic ring to activate it, either
by the resonance effect or inductive effect. This tendency was also
found in the all scavenging tests against the coumarinolignoids (1–
6).
H
O
H
O
H3CO
H
O
H
H
O
H
O
H
C
CH2
O
HO
H
H
OH
H
OCH3
Figure 2. Important HMBC correlations of 1.
H
The compounds 1–6 could be lead compounds in treatment of
oxidative-stress related human diseases. However, further in vivo
study would help in exploring the pharmacological properties of
these compounds.
Table 2
Antioxidant activities of coumarinolignoids (1–6)
S. No. Name of compounds
Antioxidant activity IC50 SEMa
(mM)
Supplementary data
1
2
3
4
5
6
7
Repenin A
Repenin B
Repenin C
Repenin D
Cleomiscosin A
Durantin A
0.530 0.08
0.420 0.09
0.450 0.10
0.510 0.07
0.612 0.10
0.625 0.09
0.043 0.07
Supplementary data associated with this article can be found, in
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The antioxidative activity was also examined in term of the
chemical structures including those of functional radical and its