Antioxidative lignans from phytochemical extract of Calocedrus formosana Florin

Yen, P.-L., Wu, C.-L., Chang, S.-T., Huang, S.-L., and Chang, H.-T. (2012). "Antioxidative lignans from phytochemical extract of Calocedrus formosana Florin," BioRes. 7(3), 4122-4131.

Abstract

Antiradical and antioxidant activities of ethanolic extract and its fractions from Calocedrus formosana Florin heartwood were investigated, and active compounds were identified by spectral analyses. Among extract and three fractions, the ethyl acetate soluble fraction had a high total phenolic content and exhibited the desirable reducing power, antiradical activity, and antioxidant activity. The compounds haplomyrfolin, O-ethyl-α-conidendral, matairesinol, 7,8-dehydro-4-O-methyl-thujaplicatin, and 5-methoxy-isosalicifoline were isolated from antioxidative activity guided fractionation of the ethyl acetate soluble fraction. Haplomyrfolin and O-ethyl-α-conidendral were for the first time isolated and identified from C. formosana. Matairesinol and 5-methoxy-isosalicifoline exhibited superior DPPH radical scavenging ability and antioxidant activity, as evaluated by TEAC assay. Results obtained in the present study revealed that ethyl acetate soluble fraction from C. formosana heartwood extract and its active compounds, matairesinol and 5-methoxy-isosalicifoline, exhibit antioxidant potential as natural nutraceuticals.

Download PDF

Full Article

Antioxidative Lignans from Phytochemical Extract of Calocedrus formosana Florin

Pei-Ling Yen, ^a Chi-Lin Wu, ^a Shang-Tzen Chang, ^a Shou-Ling Huang, ^b and Hui-Ting Chang^a,*

Keywords: Calocedrus formosana; Antioxidant activity; Lignan; Matairesinol; 5-Methoxy-isosalicifoline

Contact information: a: School of Forestry and Resource Conservation, National Taiwan University, No. 1 Section 4, Roosevelt Road, Taipei 106, Taiwan; b: Instrumentation Center, National Taiwan University, No. 1 Section 4, Roosevelt Road, Taipei 106, Taiwan. * Corresponding author: chtchang@ntu.edu.tw

INTRODUCTION

Natural products present in numerous plants are of great potential as nutraceuticals or pharmaceuticals (Clark 1996; Chan et al. 2007; Mittal et al. 2009; Garzón et al. 2010). Kuti and Konuru (2004) reported that antioxidant activity of leaf extract from Cnidoscolus spp. were highly correlated with total phenolic contents, and Cnidoscolus spp. leaves are recommended to be the source of natural antioxidant supplements. Many studies also have revealed that phenolic constituents such as flavonoids, lignans, etc., from higher plants possess marvelous antiradical and antioxidant activities (Sultana et al. 2007; Singh et al. 2009). Leaf extract (EGb 761) from Ginkgo biloba contains bioactive constituents, mainly flavonoids and terpenoids, and is one of the famous commercial complementary nutraceuticals with antiradical, antioxidant, antiplatelet, and anti-aging effects (Chan et al. 2007). Using natural nutraceuticals and alternative medicines to benefit human health is an increasing trend throughout the globe (Holst and Williamson 2008; Joseph et al. 2009).

Species of Calocedrus belonging to Cupressaceae are living fossil plants and are distributed in eastern Asia and western North America; only four species are recognized in this genus (Chen et al. 2009). Calocedrus formosana (Taiwan incense cedar) is one of the precious endemic woods in Taiwan. Ichikawa (1932) first reported that the main constituents of C. formosana heartwood oil were acidic components. Part constituents, including terpenoids, lignans, and steroids, have been isolated and identified from C. formosana wood, bark, and leaf (Lin et al. 1956; Kuo et al. 1975; Fang et al. 1985, 1990; Chiang et al. 2003; Hsieh et al. 2006). Bioactivities of natural products from C. formosana were reported in recent years, including antitumor, antioxidant, anti-inflammatory, antibacterial, antitermitic, and antifungal activities (Chao et al. 2005; Cheng et al. 2004; Chiang et al. 2003; Wang et al. 2004; Hsieh et al. 2006).

In the present study, the content of antioxidants of ethanolic extract from C. formosana heartwood and its fractions were analyzed, and the antiradical and antioxidant activities of ethanolic extract and its fractions were evaluated. In addition, the antioxi-dative lignans were isolated and identified from active fraction by chromatographic and spectroscopic methods.

EXPERIMENTAL

Plant Materials and Extraction

The heartwood of Calocedrus formosana Florin was collected from 36-year-old trees at the Experimental Forest of National Taiwan University (located in Nan-Tou county, Taiwan). The species was identified, and a voucher specimen (CF92) was deposited in National Taiwan University. Specimens were extracted twice with 95% ethanol at ambient temperature. Then, the crude extract (200 g) was further separated into an n-hexane-soluble fraction (HEXF, 42.5%), an ethyl acetate-soluble fraction (EAF, 41.9%), and a water-soluble fraction (WF, 12.4%) by liquid-liquid partition. Antioxidant activities of three fractions were evaluated to screen the active one for further separation. The active fraction, EAF, was coated onto silica gel (Silica-60, Merck 7734); the eluted solvents were n-hexane, ethyl acetate, and ethanol with different proportions. EAF (43.7 g) was separated into 11 subfractions by open column chromatography (CC) and thin layer chromatography (TLC). In order to obtain pure active compounds, high performance liquid chromatography (HPLC) was used to isolate the compounds from the active subfractions based on an activity-guided fractionation procedure.

HPLC Analysis

Active subfractions were analyzed by HPLC (Hitachi L-2130) fitted with a C18 column (Phenomenex, Luna 5u, 250 x 10 mm). The gradient mobile phase consisted of water (A) and acetonitrile (B). The flow rate was 3 mL/min. The elution program involved a linear gradient from 40% B in A for 0 to 15 min, 40 to 55% B in A by 35 min, and 55 to 100% B in A by 30 min followed by 5 min of equilibrium with 100% B. The elution profile was detected by UV detector at 254 nm. Isolated and purified compounds (ca. 10 to 25 mg) were obtained for spectral analyses and antioxidant assays.

Spectral Analyses

Structures of compounds were identified by spectroscopic methods including NMR (Nuclear magnetic resonance spectroscopy, Bruker Avanace 500 MHz), FTIR (Fourier transform infrared spectroscopy, Bio-rad FTS-40), UV/VIS (Ultraviolet and visible absorption spectroscopy, Jasco V-550), and MS (Mass spectroscopy, Finnigan MAT-958).

Determination of Total Phenolics Content

The total phenolics contents in tested specimens were determined according to the Folin-Ciocalteu procedure and expressed as milligrams per gram gallic acid equivalents (GAE). The Folin-Ciocalteu phenol reagent (0.5 mL) was mixed with 0.5 mL of a diluted sample solution. After an interval of 5 min, 1 mL of 10% aqueous sodium carbonate was added to the vial, and the mixture was allowed to stand for 8 min at ambient temperature; then the mixture was centrifuged at 12,000 rpm for 10 minutes. The absorbance of the solution was read at 730 nm. The total phenolic content was expressed as gallic acid equivalents (GAE) in milligrams per gram sample. The R-squared value of the calibration curve of gallic acid (y = 27.637x – 0.1362) was 0.9962.

DPPH Free Radical Scavenging Assay

Different concentrations of specimens (0.5 mL) were added to an ethanol solution of 1 mL of 0.15 mM DPPH (1,1-diphenyl-2-picrylhydrazyl) in test tubes. The mixture was shaken and left to stand for 30 min at room temperature. The absorbance of the solution was then measured at 517 nm with a spectrophotometer (Hitachi U-3900). IC₅₀ values are the concentrations of compounds required for a 50% decrease of the DPPH radicals (Bamoniri et al. 2010).

Reducing Power Assay

The reducing power of specimen was determined according to the method of Kapoor et al. (2009). Specimen (0.5 mL) was mixed with phosphate buffer (0.5 mL, 0.2 M, pH 6.6) and potassium ferricyanide [K₃Fe(CN)₆] (0.5 mL, 1%). The mixture was incubated at 50°C for 20 min. After cooling by ice water, 0.5 mL trichloroacetic acid (10%) was added to the mixture, and then centrifuged at 3000 rpm for 10 min. The upper layer of the solution (0.5 mL) was mixed with distilled 0.5 mL water and 0.1 mL FeCl₃ (0.1%). The absorbance of the solution was measured at 700 nm.

Total Antioxidant Activity

The ability of the specimen to scavenge ABTS^·+ radical cation was compared to trolox standard (Garzón et al. 2010). The ABTS^·+ radical cation was generated by mixing 7 mM ABTS^·+stock solution with 2.45 mM potassium persulfate and incubating for 12 to 16 h in the dark at room temperature until the reaction was complete and the absorbance was stable.

The absorbance of the ABTS^·+ solution was diluted to 0.70 (± 0.02) with water at room temperature, then 1.485 mL was mixed with 15 μL of the specimens, and the absorbance was measured at 734 nm after 6 min. All experiments were repeated three times. The percentage inhibition of absorbance was calculated and plotted as a function of the concentration of standard and specimen to determine the trolox equivalent antioxidant concentration (TEAC).

Statistical Analyses

Mean values (n ≥ 3) and standard deviations of specimens examined were calculated. The data were grouped by Scheffe’s test of the SAS system (at a level of significance of p < 0.05).

RESULTS AND DISCUSSION

Plant extracts with high phenolic phytochemicals exhibit superior antioxidant potency as the sources of nutraceuticals (Sultana et al. 2007; Enayat and Banerjee 2009). The total phenolic contents in the heartwood extract and its fractions of C. formosana were expressed as gallic acid equivalents (GAE) as shown in Table 1. Total phenolic contents of the specimens fell within the range of 161.4 to 238.5 mg of GAE/g, except for the n-hexane soluble fraction (HEXF, 33.3 mg of GAE/g). Heartwood extract (187.1 mg of GAE/g) and ethyl acetate soluble fraction (EAF, 238.5 mg of GAE/g) contained more phenolic constituents.

Table 1. Antioxidant Content and Antioxidative Activities of Ethanolic Extract of Calocedrus formosana Heartwood and Its Fractions

HEXF: n-hexane soluble fraction; EAF: ethyl acetate soluble fraction; WF: water soluble fraction; ND: not detected; * At the concentration of 1 mM

The free radical scavenging activities of specimens were assessed by DPPH assay (Table 1). Except for the HEXF, most test samples showed a superior scavenging activity against the DPPH radicals. The IC₅₀ values of EAF and heartwood extract were 10.0 and 19.2 μg/mL in DPPH assay, respectively. The TEAC assay was used to evaluate the antioxidant activity of specimens. EAF shows the same trend in TEAC and DPPH assays; it exhibited the highest antioxidant capacity (0.82 mM of trolox at the concentration of 0.5 mg/mL) among three fractions.

Reductive potentials of specimens were determined by reducing power assay as shown in Fig. 1. The reducing power of the specimen increased with increasing concentration; EAF could reduce the higher amount of Fe³⁺ ions than those of the other specimens with statistical significance. Based on the evaluations of antioxidant contents and activities of C. formosanaheartwood extract and its fractions, these results revealed that EAF is of great interest to be a potential source of natural antioxidants.

Activity-guided fractionation of the ethyl acetate soluble fraction led to the isolation of five lignan compounds, as shown in Fig. 2, including haplomyrfolin (1), O-ethyl-α-conidendral (2), matairesinol (3), 7,8-dehydro-4-O-methyl-thujaplicatin (4), 5-methoxy-isosalicifoline (5).

Fig. 1. Reducing power of the ethanolic extract and its fractions from the heartwood of C. formosana (HEXF: n-hexane soluble fraction; EAF: ethyl acetate soluble fraction; WF: water soluble fraction; * Different letters are statistically different, p < 0.05).

Fig. 2. Lignans isolated from the heartwood extract of C. formosana. (1: Haplomyrfolin; 2: O-ethyl-α-conidendral; 3: Matairesinol; 4: 7,8-Dehydro-4-O-methyl-thujaplicatin; 5: 5-Methoxy-isosalicifoline)

Spectral data of five lignan compounds are listed below:

Haplomyrfolin (1): colorless solid; C₂₀H₂₀O₆, HREI mass: 356.1252 (theor. 356.1254); UV (MeOH) λ_max nm: 218, 242, 296; IR (KBr) υ_max cm^-1: 3452, 2960, 2919, 2854, 1765, 1607, 1512, 1443, 1369, 1259, 1032, 929, 808; ¹H NMR (500 MHz, CDCl₃): δ 2.49 (1H, m, H-8’), 2.51 (H, m, H-7’a), 2.53 (H, m, H-8), 2.56 (H, m, H-7’b), 2.84 (H, dd, J=14.10, 7.15 Hz, H-7a), 2.95 (H, dd, J=14.10, 5.15 Hz, H-7b), 3.82 (3H, s, C-3’-OMe), 3.84 (1H, dd, J=9.30, 7.40 Hz, H-9’a), 4.12 (H, dd, J=9.30, 7.20 Hz, H-9’b), 5.50 (1H, br s, C-4’-OH), 5.91 and 5.92 (2H, d, J=1.40 Hz, OCH₂O), 6.44 (1H, d, J=1.80 Hz, H-2’), 6.51 (1H, dd, J=8.00, 1.80 Hz, H-6’), 6.56 (1H, dd, J=1.80, 7.80 Hz, H-6), 6.57 (1H, d, J=1.80 Hz, H-2), 6.70 (1H, d, J=7.80 Hz, H-5), 6.78 (1H, d, J=8.00 Hz, H-5’); ¹³C NMR (δc, CDCl₃, 125 MHz): 34.7 (C-7), 38.3 (C-7’), 41.3 (C-8’), 46.4 (C-8), 55.8 (C-3’-OMe), 71.2 (C-9’), 100.9 (OCH₂O), 109.4 (C-2), 108.2 (C-5), 111.0 (C-2’), 114.5 (C-5’), 121.2 (C-6’), 122.2 (C-6), 129.7 (C-1’), 131.4 (C-1), 144.4 (C-4’), 146.4 (C-4), 146.6 (C-3’), 147.9 (C-3), 178.5 (C-9).

O-ethyl-α-conidendral (2): white solid; C₂₂H₂₆O₆, HREI mass: 386.1723 (theor. 386.1724); UV (MeOH) λ_max nm: 218, 234, 295; IR (KBr) υ_max cm^-1: 3284, 2935, 2841, 1722, 1638, 1583, 1511, 1454, 1431, 1367, 1252, 1211, 1113, 986; ¹H NMR (500 MHz, CDCl₃): δ 1.18 (3H, t, J=7.05 Hz, -OCH₂CH₃), 2.06 (1H, m, H-8), 2.50 (H, m, H-8), 2.84 (1H, dd, J=14.75, 5.00 Hz, H-7a), 3.05 (H, t, J=14.75 Hz, H-7b), 3.45 (1H, m, -OCH₂CH₃), 3.53 (1H, dd, J=9.85, 8.45 Hz, H-9’a), 3.61 (1H, d, J=11.35 Hz, H-7’), 3.76 (1H, m, -OCH₂CH₃), 3.79 (3H, s, C-3-OMe), 3.84 (3H, s, C-3’-OMe), 3.87 (1H, m, H-9’b), 5.09 (1H, d, J=4.60 Hz, H-9’b), 5.32 (1H, br s, C-4’-OH), 5.51 (1H, br s, C-4-OH), 6.33 (1H, s, H-5), 6.54 (1H, s, H-2), 6.62 (1H, br s, H-2’), 6.64 (1H, dd, J=8.05, 1.60 Hz, H-6), 6.81 (1H, d, J=8.05 Hz, H-5’); ¹³C NMR (δc, CDCl₃, 125 MHz): 15.2 (C9-OCH₂CH₃), 29.2 (C-7), 45.9 (C-8), 46.1 (C-8’), 50.9 (C-7’), 55.9 (C-3-OMe), 55.9 (C-3’-OMe), 63.0 (C9-OCH₂CH₃), 72.2 (C-9’), 103.8 (C-9), 110.5 (C-2’), 111.1 (C-2), 114.2 (C-5’), 115.0 (C-5), 121.6 (C-6’), 128.2 (C-1), 132.8 (C-6), 136.4 (C-1’), 143.5 (C-4), 144.4 (C-4’), 145.0 (C-3), 146.7 (C-3’). The ethyl group in O-ethyl-α-conidendral is possibly derived from ethanol used for extraction.

Matairesinol (3): white solid; C₂₀H₂₂O₆, HREI mass: 358.1408 (theor. 356.1411); UV (MeOH) λ_max nm: 217.5, 234, 285.5; IR (KBr) υ_max cm^-1: 3434, 2937, 2846, 1758, 1606, 1516, 1452, 1371, 1274, 1123, 1031; ¹H NMR (500 MHz, CDCl₃): δ 2.46 (1H, m, H-8’), 2.52 (H, m, H-7’a), 2.54 (H, m, H-8), 2.58 (H, m, H-7’b), 2.85 (H, dd, J=14.10, 7.05 Hz, H-7a), 2.93 (H, dd, J=14.10, 5.20 Hz, H-7b), 3.80 (6H, s, OMe), 3.86 (1H, dd, J=9.15, 7.35 Hz, H-9’a), 4.13 (H, dd, J=8.95, 7.35 Hz, H-9’b), 5.53 (1H, br s, C-4’-OH), 5.55 (1H, br s, C-4-OH), 6.39 (1H, d, J=1.80 Hz, H-2’), 6.49 (1H, dd, J=8.00, 1.80 Hz, H-6’), 6.57 (1H, d, J=1.80 Hz, H-6), 6.59 (1H, s, H-2), 6.78 (1H, d, J=8.00 Hz, H-5’), 6.79 (1H, d, J=7.80 Hz, H-5); ¹³C NMR (δc, CDCl₃, 125 MHz): 34.5 (C-7), 38.3 (C-7’), 41.0 (C-8’), 46.5 (C-8), 55.7 (C-3’-OMe), 55.8 (C-3-OMe), 71.3 (C-9’), 110.9 (C-2’), 111.4 (C-2), 114.0 (C-5’), 114.4 (C-5), 121.3 (C-6’), 122.0 (C-6), 129.5 (C-1’), 129.7 (C-1), 144.3 (C-4’), 144.5 (C-4), 146.6 (C-3’), 146.7 (C-3), 178.8 (C-9).

7,8-Dehydro-4-O-methyl-thujaplicatin (4): colorless solid; C₂₁H₂₂O₇, HREI mass: 386.1373 (theor. 386.1360); UV (MeOH) λ_max nm: 211.5, 237, 317.5; IR (KBr) υ_max cm^-1: 3433, 2937, 2846, 1758, 1606, 1516, 1452, 1432, 1372, 1274, 1153, 1031; ¹H NMR (500 MHz, CDCl₃): δ 2.58 (H, dd, J=14.20, 3.95 Hz, H-7’a), 3.01 (H, dd, J=14.10, 4.10 Hz, H-7’b), 3.77 (H, m, H-8’), 3.87 (3H, s, C-3-OMe), 3.88 (3H, s, C-4-OMe), 3.95 (3H, s, C-3’-OMe), 4.24 (1H, dd, J=9.00, 6.6 Hz, H-9’a), 4.28 (H, dd, J=9.00, 1.80 Hz, H-9’b), 5.50 (1H, br s, C-4’-OH), 5.86 (1H, br s, C-5-OH), 6.60 (1H, d, J=1.80 Hz, H-2), 6.68 (1H, d, J=7.90 Hz, H-6’), 6.69 (1H, s, H-2’), 6.82 (1H, d, J=7.90 Hz, H-5’), 6.95 (1H, d, J=1.80 Hz, H-6), 7.45 (1H, s, H-7); ¹³C NMR (δc, CDCl₃, 125 MHz): 37.6 (C-7’), 40.1 (C-8’), 55.9 (C-3’-OMe), 56.0 (C-3-OMe), 61.1 (C-4-OMe), 69.8 (C-9’), 107.6 (C-2), 108.6 (C-6), 111.3 (C-2’), 114.5 (C-5’), 121.5 (C-6’), 127.7 (C-1), 129.8 (C-8), 129.8 (C-1’), 137.0 (C-4), 137.1 (C-7), 144.6 (C-4’), 146.7 (C-3’), 149.5 (C-5), 152.3 (C-3), 172.5 (C-9).

5-Methoxy-isosalicifoline (5): light yellowish solid; C₂₁H₂₂O₇, HREI mass: 386.1368 (theor. 386.1360); UV (MeOH) λ_max nm: 216, 243, 346; IR (KBr) υ_max cm^-1: 3414, 2935, 2845, 1738, 1641, 1604, 1516, 1456, 1428, 1357, 1210, 1117, 1033; ¹H NMR (500 MHz, CDCl₃): δ 2.62 (H, dd, J=14.55, 4.25 Hz, H-7’a), 3.05 (H, dd, J=14.55, 4.05 Hz, H-7’b), 3.84 (H, m, H-8’), 3.81 (3H, s, C-5-OMe), 3.87 (6H, s, C-3-OMe, C-3’-OMe), 4.22-4.27 (2H, m, H-9’), 5.62 (1H, br s, C-4’-OH), 5.93 (1H, br s, C-4-OH), 6.60 (1H, br s, H-2’), 6.65 (1H, d, J=8.20 Hz, H-6’), 6.80 (2H, s, H-2, H-6), 6.82 (1H, d, J=8.20 Hz, H-5’), 7.47 (1H, s, H-7); ¹³C NMR (δc, CDCl₃, 125 MHz): 37.3 (C-7’), 39.4 (C-8’), 55.8 (C-5-OMe), 56.4 (C-3-OMe), 56.4 (C-3’-OMe), 69.7 (C-9’), 107.3 (C-2), 107.3 (C-6), 111.5 (C-2’), 114.6 (C-5’), 121.0 (C-6’), 125.3 (C-1’), 125.8 (C-1), 129.5 (C-8), 137.0 (C-4), 137.7 (C-7), 144.6 (C-4’), 146.6 (C-5), 147.2 (C-3), 147.2 (C-3’), 172.6 (C-9).

The compounds haplomyrfolin, matairesinol, 7,8-dehydro-4-O-methyl-thujaplic-atin, and 5-methoxy-isosalicifoline belong to the dibenzylbutyrolactone type of lignan; compound O-ethyl-α-conidendral is the aryltetralin-type lignan. Among these lignans, haplomyrfolin and O-ethyl-α-conidendral are isolated and identified for the first time from Calocedrus formosana. Lignans occur commonly in the higher plants, and they have been reported to possess a variety of biological properties, including antioxidant activities (Willfor et al. 2006; Yamauchi et al.2006).

The antiradical activities of the lignan compounds are shown in Table 2; the activity of lignans decreased in the following order: haplomyrfolin > matairesinol > 5-methoxy-isosalicifoline > 7,8-dehydro-4-O-methyl-thujaplicatin > O-ethyl-α-conidendral in terms of the DPPH assay. Haplomyrfolin and matairesinol exhibited a superior ability to scavenge DPPH radicals (with IC₅₀ values of 7.9 and 9.9 μM, respectively), and the capacity of these compounds was comparable to that of catechin (positive control, IC₅₀ = 8.6 μM) without the statistical significant difference (p < 0.05). 5-Methoxy-isosalicifoline also had a good antiradical activity with an IC₅₀ value of 12.2 μM. Antioxidant activities of isolated lignans were evaluated as the trolox equivalent antioxidant concentration (TEAC); TEAC values ranged between 1.25 and 1.92 mM Trolox. 5-Methoxy-isosalicifoline had the highest TEAC value (1.92 mM trolox), followed by matairesinol (1.69 mM trolox). Haplomyrfolin exhibited the high antiradical activity and did not show the higher TEAC values. Based on the above results, matairesinol and 5-methoxy-isosalicifoline had better antiradical and antioxidant activities among these lignans. As for the effects of structure of compound on its antiradical and antioxidant activities, both matairesinol and 5-methoxy-isosalicifoline possess the dibenzylbutyrolactone skeleton with hydroxyl group at C4 and C4’ positions.

Table 2. Antiradical and Antioxidant Activities of Lignan Compounds

* Mean value of three replicates ± standard deviation; numbers followed by different superscript letters are statistically different (p < 0.05).

Multiple antioxidant products from forest bioresources, including leaf, fruit, stem, etc., have been investigated for applications in the food, pharmaceutical, and other industries (Sultana et al. 2007; Chan et al. 2007; Ebringerova et al. 2008; Kang et al. 2011; Luis et al. 2012). Antioxidant extract and compounds from C. formosana are worth further research and trial for complementary and alternative nutraceuticals.

CONCLUSIONS

In the total antioxidant assay, C. formosana heartwood extract showed good performance with a TEAC value of 0.67 mM of trolox at a concentration of 0.5 mg/mL; among three fractions of extract, ethyl acetate soluble fraction possesses highest antioxidant activity (0.82 mM of trolox) than the other fractions.
Five lignans, including haplomyrfolin, O-ethyl-α-conidendral, matairesinol, 7,8-dehydro-4-O-methyl-thujaplicatin, and 5-methoxy-isosalicifoline were isolated and identified from ethyl acetate soluble fraction. Among these compounds, haplomyrfolin and O-ethyl-α-conidendral were first found from C. formosana. Among these lignans, matairesinol, and 5-methoxy-isosalicifoline had preferable antiradical and antioxidant activities.
Based on the evaluations of antioxidant contents and activities of ethyl acetate soluble fraction and isolated lignans from C. formosana heartwood extract, it was revealed that the ethyl acetate soluble fraction, matairesinol, and 5-methoxy-isosalicifoline are of great interest to be a potential source of natural antioxidants.

ACKNOWLEDGMENTS

The authors are grateful to the Forestry Bureau, Taiwan, for the generous financial support and the National Center for High-Performance Computing (NCHC) in Hsinchu, Taiwan for the chemistry database search.

REFERENCES CITED

Bamoniri, A., Ebrahimabadi, A. H., Mazoochi, A., Behpour, M., Kashi, F. J., and Batooli, H. (2010). “Antioxidant and antimicrobial activity evaluation and essential oil analysis of Semenovia tragioides Boiss from Iran,” Food Chemistry 122, 553-558.

Chan, P.C., Xia, Q., and Fu, P.P. (2007). “Ginkgo biloba leave extract: Biological, medicinal, and toxicological effects,” Journal of Environmental Science and Health – Part C: Environmental Carcinogenesis & Ecotoxicology Reviews 25, 211-244.

Chao, L. K., Hua, K. F., Hsu, H. Y., Su, Y. C., and Chang, S. T. (2005). “Bioactivity assay of extracts from Calocedrus macrolepis var. formosana bark,” Bioresource Technology 97, 2462-2465.

Chen, C. H., Huang, J. P., Tsai, C. C., and Chaw, S. M. (2009). “Phylogeny of Calocedrus (Cupressaceae), an eastern Asian and western North American disjunct gymnosperm genus, inferred from nuclear ribosomal nrITS sequences,” Botanical Studies 50, 425-433.

Cheng, S. S., Wu, C. L., Chang, H. T., Kao, Y. T., and Chang, S. T. (2004). “Antitermitic and antifungal activities of essential oil of Calocedrus formosana leaf and its composition,” Journal of Chemical Ecology 30, 1957-1967.

Chiang, Y. M., Liu, H. K., Lo, J. M., Chien, S. C., Chan, Y. F., Lee, T. H., Su, J. K., and Kuo, Y. H. (2003). “Cytotoxic constituents of the leaves of Calocedrus formosana,” Journal of the Chinese Chemical Society 50, 161-166.

Clark, A. M. (1996). “Natural products as a resource for new drugs,” Pharmaceutical Research 13, 1133-1141.

Ebringerova, A., Hromadkova, Z., Kostalova, Z., and Sasinkova, V. (2008). “Chemical valorization of agricultural by-products: Isolation and characterization of xylan-based antioxidants from almond shell biomass,” BioResources 3, 60-70.

Enayat, S., and Banerjee, S. (2009). “Comparative antioxidant activity of extracts from leaves, bark and catkins of Salix aegyptiaca sp.,” Food Chemistry 116, 23-28.

Fang, J. M., Jan, S. T., and Cheng, Y. S. (1985). “(+)-Calocedrin, a lignan dihydroanhydride from Calocedrus formosana,” Phytochemistry 24, 1863-1864.

Fang, J. M., Liu, M. Y., and Cheng, Y. S. (1990). “Lignans from wood of Calocedrus formosana,” Phytochemistry 29, 3048-3049.

Holst, B., and Williamson, G. (2008). “Nutrients and phytochemicals: From bioavailability to bioefficacy beyond antioxidants,” Current Opinion in Biotechnology 19, 73-82.

Hsieh, C. L., Tseng, M. H., Shao, Y. Y., Chang, J. Y., Kuo, C. C., Chang, C. Y., and Kuo, Y. H. (2006). “C35 Terpenoids from the bark of Calocedrus macrolepis var. formosana with activity against human cancer cell lines,” Journal of Natural Products 69, 1611-1613.

Ichikawa, N. (1932). “Studies on the volatile acid of Libocedrus macrolepis, Benth et Hook. Part I,” Journal of the Chemical Society of Japan 53, 353-365.

Joseph, J., Cole, G., Head, E., and Ingram, D. (2009). “Nutrition, brain aging, and neurodegeneration,” Journal of Neuroscience 29, 12795-12801.

Kang, S., Li, B., Chang, J., and Fan, J. (2011). “Antioxidant abilities comparison of lignins with their hydrothermal liquefaction products,” BioResources 6, 243-252.

Kapoor, I. P. S., Singh, B., Singh, G., De Heluani, C. S., De Lampasona, M. P., and Catalan, C. A. N. (2009). “Chemistry and in vitro antioxidant activity of volatile oil and oleoresins of black pepper (Piper nigrum),”Journal of Agricultural and Food Chemistry 57, 5358-5364.

Kuo, Y. H., Chang, B. H., and Lin, Y. T. (1975). “Studies on the extractive constituents of the bark of Libocedrus formosana Florin I. The structure of 6α-hydroxy-7-oxo-ferruginol,” Journal of the Chinese Chemical Society 22, 49-52.

Kuti, J. O., and Konuru, H. B. (2004). “Antioxidant capacity and phenolic content in leaf extracts of tree spinach (Cnidoscolus spp.),” Journal of Agricultural and Food Chemistry 52, 117-121.

Lin, Y. T., Lo, T. B., and Lin, T. H. (1956). “Study on the extractive constituents from the wood of Libocedrus formosana Florin II. Interconversions between isoshanoic acid and thujic acid,” Journal of the Chinese Chemical Society 3, 36-40.

Luis, A., Gil, N., Amaral, M. E., Domingues, F., and Duarte, A. P. (2012). “Ailanthus altissima (Miller) Swingle: A source of bioactive compounds with antioxidant activity,” BioResources7, 2105-2120.

Singh, H. P., Mittal, S., Kaur, S., Batish, D. R., and Kohli, R. K. (2009). “Chemical composition and antioxidant activity of essential oil from residues of Artemisia scoparia,” Food Chemistry 114, 642-645.

Sultana, B., Anwar, F., and Przybylski, R. (2007). “Antioxidant activity of phenolic components present in barks of Azadirachta indica, Terminalia arjuna, Acacia nilotica, and Eugenia jambolana Lam. Trees,” Food Chemistry 104, 1106-1114.

Wang, S. Y., Wu, J. H., Cheng, S. S., Lo, C. P., Chang, H. N., Shyur, L. F., and Chang, S. T. (2004). “Antioxidant activity of extracts from Calocedrus formosana leaf, bark, and heartwood,” Journal of the Japan Wood Research Society 50, 422-426.

Willfor, S. M., Smeds, A. I., and Holmbom, B. R. (2006). “Chromatographic analysis of lignans,” Journal of Chromatography A 1112, 64-77.

Yamauchi, S., Sugahara, T., Nakashima, Y., Abe, K., Hayashi, Y., Akiyama, K., Kishida, T., and Maruyama, M.(2006). “Effect of benzylic oxygen on the cytotoxic activity for colon 26 cell line of phenolic lignans,” Bioscience, Biotechnology, and Biochemistry 70, 2942-2947.

Article submitted: May 2, 2012; Peer review completed: July 3, 2012; Revised version received and accepted: July 18, 2012; Published: July 19, 2012.