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Journal of Thai Traditional & Alternative Medicine Vol. 5 No. 1 January - April 2007 Ú˜

6.17 d, J= 2.0 Hz. The coupling constant value showed
Table1 Total antioxidant capacity of the plant extracts evaluated these two protons to be meta to each other. A three-
by ferric reducing/antioxidant power (FRAP) assay. proton singlet at δ 2.69 accounted for a methyl group
Curcuma comosa Roxb. Total antioxidant capacity attached to an aromatic keto group. The rest of the
extracts (1 mg/mL) (μM vitamin C equivalence)* 1 H-NMR spectrum clearly revealed the presence of a
glucoside moiety in 4,6-dihydroxy-2-O-(β-D-
Zcc(R) 6931 ±407.70
glucopyranosyl)acetophenone (mp 210-212˚C) as
Zcc(R)-E-1 2023.12 ±154.73
shown in Table 3. The signal of a quaternary carbon
Zcc(R)-E-2 854.11 ±42.45
13
at 202.7 in the C-NMR spectrum confirmed the pres-
Zcc(R)-E15 1064.73 ±60.96
ence of a keto functional group in the molecule as
*Data are presented as Mean ± SEM shown in Table 4. Its IR spectrum (KBr) showed ab-
-1
sorption at 3434 cm indicating the presence of hy-
droxyl groups (O-H); the broad, intense absorption
-1
Table 2 Cytotoxicity of doxorubicin and plant extract in HeLa cells. band at 1637 cm was indicative of a conjugated
Compound IC (μg/mL)*
50
Doxorubicin 0.11 0.01
1
Zcc(R) 1.70 0.21 Table 3 H-NMR Spectral Data of 4,6-dihydroxy-2-O-(β-D-
Zcc(R)-E-1 1.47 0.46 glucopyranosyl) acetophenone in CD3OD.
Zcc(R)-E-2 11.56 2.13
Position δ (ppm), J(Hz)
H
Zcc(R)-E15 4.44 0.85
3 6.17(1H, d,2.0)
*Data are presented as Mean ± SEM
5 5.95(1H, d, 2.0)
OCCH 3 2.69

tested. The assay showed intra and inter-day vari-
ability at less than 10 per cent. Table 4 C-NMR Data for 4,6-dihydroxy-2-O-(β-D-
13
glucopyranosyl)acetophenone in CD OD
5. Cytotoxicity Effect of Plant Extracts 3
Table 2 shows the cytotoxic effects of doxorubi- 4,6-dihydroxy-2-O-
cin and the plant extracts on HeLa cells. The IC 50 Position (β-D-glucopyranosyl)
(concentrations that kill 50% of the cells) demonstrated acetophenone
that doxorubicin was (15-fold more potent than Zcc(R) 1 104.5
(IC =0.11 ± 0.01 vs 1.70 ± 0.21 g/ml, respectively). 2 165.1
50
Further fractionation did not increase the potency. 3 91.6

Discussion 4 165.4
5
94.9
The ethanol extract of C. comosa rhizomes pos- 6 160.3
sesses high antioxidant power and cytotoxic effect 1' 102.2
on HeLa cells. These results prompted us to carry 2' 73.9 a a
out the bioassay-guided separation of the active con- 3' 70.9 a
67.4
4'
stituent from the rhizomes of C. comosa. Chromato- 5' 74.6 a
graphic isolation of the ethanol extract resulted in 6' 63.0 a
the isolation of a phloracetophenone glucoside, com- C=O 202.7
1
pound A. The H-NMR spectrum revealed the pres- CH 3 32.7
ence of two aromatic protons δ 5.95 d, J= 2.0 Hz ; a Assignments within a column may be interchanges.