The antioxidant activity of the curcuminoids of
The antioxidant activity of
In a search for sources of natural cardiovascular protective agents for pharmaceutical, food, and nutraceutical applications, we investigated the antioxidant effect of the methanol extracts and essential oils of
Structures of major compounds from
The chemicals used in this study were of analytical grade that include methanol, dimethyl sulfoxide (DMSO) and sodium citrate (Merck, Darmstadt, Germany). Camphor, geranyl acetate, zerumbone,
The rhizomes of
The defatted rhizome extract (14 g) of
Orange crystals, mp 184°C. HRESIMS:
Orange crystals, mp 172°C. Its molecular formula was C20H18O5 as indicated by HRESIMS:
Orange crystals, mp 222°C. HRESIMS for C19H16O4
The fresh rhizomes of
Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) analyses were used for the identification of the essential oil components. The components were separated using a Shimadzu GC-2010 equipped with a flame ionizing detector (FID) and a DB-5 (30 m
The essential oils of
The use of human whole blood in this study was approved by the Ethics Committee of Universiti Kebangsaan Malaysia (UKM) (approval no. FF-120-2007). All subjects were healthy volunteers aged 24–70 yrs, normolipidemic, nonsmokers, having not taken any medications including vitamin supplements within the last 2 weeks, and fasting for the last 8 h. Venous blood was drawn from the volunteers, and 9 volumes of blood were added into 1 volume of 3.8% (w/v) sodium citrate solution as an anticoagulant. Plasma was obtained by centrifugation at 2000 g for 20 min. LDL was isolated by density gradient ultracentrifugation using a method developed by Graham et al. [
LDL (200
The inhibition of copper-catalysed LDL oxidation was determined using TBARS assay [
The percentage inhibition of LDL oxidation was calculated as follows:
All the data are presented as means
It was found that
The chemical composition of the essential oils of
Chemical constituents of the rhizome oils of
Compound | Percentage | RI | Method of identification | |
---|---|---|---|---|
|
|
|||
|
— | tr | 931 | a, b |
|
— | 0.3 | 940 | a, b, c |
Camphene | — | 0.7 | 956 | a, b, c |
|
— | 0.1 | 976 | a, b, c |
Cis-Pinane | — | 0.1 | 986 | a |
Myrcene | — | 0.1 | 991 | a, b, c |
|
1.1 | tr | 1009 | a, b, c |
|
0.2 | 0.1 | 1016 | a, b, c |
p-Cymene | 0.2 | — | 1029 | a, b, c |
1,8-Cineole | 0.3 | 0.1 | 1034 | a, b, c |
( |
— | 0.1 | 1037 | a, b, c |
|
— | tr | 1063 | a, b, c |
Terpinolene | 0.3 | — | 1090 | a, b, c |
6,7-Epoxymyrcene | — | tr | 1093 | a |
Camphor | — | 5.4 | 1156 | a, b, c |
Cis-dehydro- |
— | 0.3 | 1160 | a, b |
|
— | 0.3 | 1167 | a, b, c |
Terpinen-4-ol | — | 0.2 | 1177 | a, b, c |
Ethyl-4E-octenoate | — | 0.1 | 1187 | a |
Dihydro citronellol acetate | — | 0.1 | 1321 | a |
|
— | 0.1 | 1351 | a, b |
( |
— | 0.1 | 1364 | a |
n-Undecanol | — | tr | 1370 | a, b |
Geranyl acetate | 2.5 | tr | 1382 | a, b, c |
|
— | tr | 1388 | a, b |
|
1.5 | — | 1389 | a, b |
Methyl perillate | — | 0.1 | 1394 | a |
( |
— | 0.2 | 1407 | a, b, c |
|
0.9 | 0.6 | 1414 | a, b |
Methyl undecanoate | — | 0.1 | 1428 | a |
|
— | 0.1 | 1439 | a, b, c |
( |
— | 0.2 | 1443 | a, b |
( |
0.3 | — | 1444 | a, b, c |
|
— | 0.4 | 1448 | a, b |
( |
0.2.0 | 1.2 | 1457 | a, b |
|
0.1 | — | 1460 | a |
( |
— | tr | 1467 | a, b, c |
Ar-Curcumene | 1.2 | 13.2 | 1493 | a, b, c |
|
0.4 | 2.6 | 1481 | a, b |
|
0.2 | 0.6 | 1505 | a, b |
Zingiberene | 1.7 | — | 1506 | a, b, c |
( |
— | 2.6 | 1516 | a, b |
|
0.8 | 17.1 | 1523 | a, b, c |
|
1.9 | 0.4 | 1538 | a, b |
1,10-Decanediol | — | 0.4 | 1549 | a, b |
( |
0.3 | 1.2 | 1567 | a, b |
Ar-Turmerol | 0.3 | — | 1571 | a, b, c |
Caryophyllene oxide | 0.3 | 0.5 | 1581 | a, b, c |
Thujopsan-2- |
— | 0.3 | 1587 | a |
Ar-Dihydro-turmerone | 1.0 | — | 1592 | a, b |
Sesquithuriferol | — | 0.2 | 1605 | a |
Geranyl isovalerate | 0.3 | — | 1607 | a |
1,10-Di-epi-cubenol | — | 0.4 | 1619 | a |
( |
3.6 | — | 1621 | a, b |
10-Epi- |
0.4 | — | 1624 | a |
Citronellyl pentanoate | — | 5.7 | 1626 | a, b |
1-Epi-cubenol | 0.8 | — | 1629 | a |
|
0.2 | — | 1632 | a, b |
Cis-cadin-4-en-7-ol | — | 0.8 | 1637 | a |
Hinesol | 0.4 | — | 1642 | a, b |
Cubenol | 0.3 | 0.5 | 1647 | a, b |
|
1.3 | — | 1651 | a, b |
|
— | 0.8 | 1654 | a, b |
( |
1.3 | — | 1655 | a, b |
( |
— | 0.7 | 1661 | a |
14-Hydroxy-9-epi-( |
0.4 | — | 1670 | a |
( |
— | 0.9 | 1668 | a |
|
— | 3.5 | 1687 | a, b |
Ar-Turmerone | 45.8 | — | 1689 | a, b, c |
Ar-Curcumen-15-al | — | 0.8 | 1712 | a |
14-Hydroxy- |
0.2 | — | 1714 | a |
1-Phenyl-hepta-1,3,5-triyne | — | 0.3 | 1721 | a |
Curcumenol | 18.2 | — | 1724 | a, b |
4-Hydroxy-3-methoxy-cinnamaldehyde | — | 0.9 | 1728 | a |
Zerumbone | 1.4 | — | 1730 | a, b, c |
Chamazulene | — | 0.3 | 1732 | a |
|
— | 0.1 | 1745 | a, b |
|
— | 0.2 | 1749 | a |
|
0.2 | — | 1758 | a |
|
0.3 | — | 1762 | a |
|
1.1 | — | 1767 | a, b |
Xanthorrhizol | — | 31.9 | 1768 | a, b, c |
|
1.6 | — | 1782 | a, b |
Butyl dodecanoate | — | 0.2 | 1786 | a |
8-Cedren-14-ol acetate | 0.8 | — | 1789 | a, b |
|
2.3 | — | 1795 | a, b |
| ||||
Total | 96.3 | 97.7 |
Percentages were calculated on the basis of results obtained on column DB 5; RI: retention index; a: retention index; b: mass fragmentation; c: co-chromatography with authentic samples.
The methanol extracts and essential oils of
Percentage inhibition and IC50 value (
Sample | Concentration ( |
Inhibition (%) | IC50 ( |
---|---|---|---|
6.25 | 84.14 ± 0.13 | ||
3.13 | 83.77 ± 0.13 | ||
|
1.56 | 73.18 ± 0.78 | 0.31 ± 0.01 |
0.78 | 68.73 ± 0.79 | ||
0.39 | 50.45 ± 0.20 | ||
| |||
12.5 | 91.94 ± 0.92* | ||
6.25 | 88.04 ± 0.52 | ||
|
3.13 | 77.82 ± 0.92 | 0.78 ± 0.03 |
1.56 | 62.23 ± 0.13 | ||
0.78 | 50.89 ± 1.05 | ||
| |||
1.56 | 98.81 ± 0.10* | ||
0.78 | 93.57 ± 0.56 | ||
Demethoxycurcumin | 0.39 | 84.23 ± 1.38 | 0.11 ± 0.01 (0.16 |
0.20 | 64.42 ± 3.10 | ||
0.10 | 47.83 ± 3.25 | ||
| |||
1.56 | 93.20 ± 0.59* | ||
0.78 | 88.71 ± 0.98 | ||
Bisdemethoxycurcumin | 0.39 | 80.87 ± 1.67 | 0.05 ± 0.01 (0.33 |
0.20 | 71.90 ± 2.45 | ||
0.10 | 56.01 ± 0.71 | ||
| |||
1.56 | 90.58 ± 0.82* | ||
0.78 | 89.09 ± 0.95 | ||
Curcumin | 0.39 | 78.25 ± 1.90 | 0.06 ± 0.01 (0.15 |
0.20 | 58.15 ± 2.89 | ||
0.10 | 50.39 ± 3.43 | ||
| |||
5.00 | 76.3 ± 0.6 | ||
2.50 | 74.2 ± 0.2 | ||
Probucol | 1.25 | 70.3 ± 0.1 | 0.30 ± 0.1 (0.57 |
0.63 | 62.1 ± 1.6 | ||
0.31 | 48.9 ± 0.1 |
Probucol was used as a positive control. Values are presented as mean ± SEM (
Percentage inhibition and IC50 value (
Sample | Concentration ( |
Inhibition (%) | IC50 ( |
---|---|---|---|
25 | 78.8 ± 1.2* | ||
12.5 | 56.4 ± 1.0 | ||
|
6.25 | 44.8 ± 0.4 | 7.8 ± 0.2 |
3.13 | 27.5 ± 1.5 | ||
1.56 | 20.0 ± 0.8 | ||
| |||
25 | 86.9 ± 2.3* | ||
12.5 | 83.2 ± 1.2 | ||
|
6.25 | 64.0 ± 1.3 | 2.2 ± 0.1 |
3.13 | 57.8 ± 4.6 | ||
1.56 | 49.4 ± 0.2 | ||
| |||
12.5 | 98.0 ± 0.7* | ||
6.25 | 87.5 ± 2.0 | ||
Xanthorrhizol | 3.13 | 84.5 ± 2.5 | 0.4 ± 0.1 (1.9 |
1.56 | 77.5 ± 0.8 | ||
0.78 | 64.6 ± 1.7 | ||
| |||
12.5 | 85.6 ± 0.7* | ||
6.25 | 72.8 ± 1.0 | ||
Ar-Turmerone | 3.13 | 62.2 ± 1.7 | 2.2 ± 0.1 (10.2 |
1.56 | 41.7 ± 1.2 | ||
0.78 | 24.6 ± 0.8 | ||
| |||
25 | 69.9 ± 0.3* | ||
12.5 | 58.1 ± 0.3 | ||
Zerumbone | 6.25 | 55.9 ± 0.7 | 5.4 ± 0.4 (24.9 |
3.13 | 49.0 ± 0.3 | ||
1.56 | 27.6 ± 2.9 | ||
| |||
Geranyl acetate | 25 | 26 ± 2.6 | |
Zingiberene | 25 | 16 ± 1.9 | |
Ar-Curcumene | 25 | 4.6 ± 1.2 | — |
|
25 | 7.8 ± 1.5 | |
Camphor | 25 | 11.2 ± 0.4 | — |
Values are presented as mean ± SEM (
The antioxidant activity of the isolated curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin) and the 8 standard compounds (xanthorrhizol, ar-turmerone, ar-curcumene,
Xanthorrhizol was found to be the most active compound in the oil of
Based on the results of the LDL antioxidant assays on the methanol extracts, essential oils, isolated compounds, and standard samples, relationships between the antioxidant activity and the chemical contents can be deduced. The results suggest that the strong antioxidant activity of the methanol extracts of the plants is due to the presence of high amounts of curcuminoids. The higher activity of the methanol extract of
The methanol extracts and essential oils of
The authors declare that they have no conflict of interests.
The work was supported by the Ministry of Agriculture, Malaysia, under the NKEA Research Grant Scheme (NRGS) (Grant no. NH0811D003).