Phytochemical investigation of Eurycoma longifolia roots collected in Gia Lai province, Viet Nam

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Cite this paper: Vietnam J. Chem., 2020, 58(5), 705-710

DOI: 10.1002/vjch.202000126

Article

Phytochemical investigation of Eurycoma longifolia roots collected in

Gia Lai province, Viet Nam

Vo Khanh Ha¹, Truong Thi Minh Hanh², Pham Cam Nam², Giang Thi Kim Lien³,

Mai Thi Phuong Chi⁴, Tran Thi Phuong Thao^5,6*

¹Department of Science and Technology, Quality Assurance and Testing Centre 2,

2 Ngo Quyen street, Da Nang City 50000, Viet Nam

²University of Science and Technology, The University of Da Nang,

54 Nguyen Luong Bang street, Da Nang City 50000, Viet Nam

³The University of Da Nang, 41 Le Duan street, Da Nang City 50000, Viet Nam

⁴University of Technology and Education, The University of Da Nang,

48 Cao Thang street, Da Nang City 50000, Viet Nam

⁵Institute of Chemistry, Vietnam Academy of Science and Technology (VAST),

18 Hoang Quoc Viet road, Cau Giay district, Hanoi 10000, Viet Nam

⁶Graduate University of Science and Technology, VAST,

18 Hoang Quoc Viet road, Cau Giay district, Hanoi 10000, Viet Nam

Received July 24, 2020; Accepted August 7, 2020

Abstract

From the roots of Eurycoma longifolia, seven compounds including β-carboline-2N-oxide-1-propionic acid (1),

9,10-dimethoxycanthin-6-one (2), β-carboline-1-propionic acid (3), infractine (4), eurylene (5), eurycomanone (6),

14,15-β-hydroxyklaineanol (7) were isolated. Their structures were determined by means of spectroscopic methods

(UV, IR, HR-ESIMS, 1D and 2D NMR). Compound (1) has been isolated for the first time from nature and compound

(4) has been isolated for the first time from Eurycoma longifolia.

Keywords. Eurycoma longifolia, β-carboline-2N-oxide-1-propionic acid, β-carboline-1-propionic acid, 9,10-

dimethoxycanthin-6-one, infractin, eurylene, eurycomanone, 14,15-β-hydroxyklaineanol.

1. INTRODUCTION

From Eurycoma longifolia roots collected in Gialai

province, Vietnam, one squalene derivative (5), four

Eurycoma longifolia Jack (Simaroubaceae) is a β-carboline alkaloids (1-4) and two quassinoids (6,

traditional medicine distributed in Southeast Asia. In 7) were identified. Compound 4 (infractin) has been

Vietnam, it is found in the middle and Southeast of isolated for the first time from this plant and

Vietnam.^[1]All the parts of this plant (leaves, barks, compound

(β-carboline-2N-oxide-1-propionic

fruits and roots) can be used in folk medicine. acid) has been isolated for the first time from nature.

Especially the roots of Eurycoma longifolia are very Their structures were elucidated by analysis of

common used in Vietnamese traditional medicine to spectral data and comparison with the published

treat poor blood, dyspepsya, osteoarthritis, colds, data.

fevers and poisoning diseases.^[1]Phytochemistry

study of this plant led to the isolation of many 2. MATERIAL AND METHODS

bioactive compounds such as quassinoid,

triterpenoid, alkaloid, coumarin, squalene and

2.1.Plant materials

biphenyl-neo-lignan.^[2]It has been reported that this

plant has many biological activities, such as Eurycoma longifolia roots were collected in Gia Lai

anticancer,^[3]antiinflammatory,^[4]hypoglycemic,^[5]province, Vietnam in April 2018 and identified by

anti-gout activity...^[6]

Mr. Nguyen The Anh (Institute of Chemistry,

Vietnam Journal of Chemistry

Tran Thi Phuong Thao et al.

VAST). A voucher specimen (EL01) was deposited under reduced pressure to obtain the corresponding

in Institute of Chemistry, Vietnam Academy of extracts. The n-hexane extract (4.1 g) was

Science and Technology, 18 Hoang Quoc Viet, Cau chromatographed on a silica gel column, eluting

Giay Distr., Hanoi, Viet Nam.

with DCM/MeOH (95:5 to 90:10) to obtain 10

fractions (Fr.1-10). Compound 5 (6 mg) was

obtained from fraction Fr.6 as a white crystall. The

ethyl acetate extract (35 g) was subjected to a silica

2.2. General experiment procedures

NMR spectra were measured on a Bruker Avance gel column with an elution of DCM/MeOH (95:5 to

500 spectrometer. HR-ESI-MS spectra were 80:20) to afford 90 fractions (Fr.1-90). Fraction

recorded on SCEIX X500R QTOF (USA). ESI-MS Fr.25 gave a white solid which was then washed

spectra were obtained from Agilent 1100 mass with cold DCM to give compound 6 (20 mg).

Fraction Fr.34 was further purified by RP-18 column

chromatography (MeOH/H₂O 1:1) to obtain

compound 7 (25 mg).

spectrometer. Silica gel (230-400 mesh), Sephadex

LH-20, diaion HP-20 using for column

chromatography were purchased from Merck

(Darmstadt, Germany). RP-18 resins (30-50 μm)

were purchased from Fujisilica Chemical Ltd, Japan.

Precoated silica gel 60 and RP-18 F_254Splates were

used for TLC.

β-carboline-2N-oxide-1-propionic acid (1):

Yellow powder, C₁₄H₁₂N₂O_3;ESI-MS (m/z): 257.6

[M+H]⁺, 255.8 [M]; HR-ESIMS: 255.0775 [M-H]^-

(calculated for C₁₄H₁₁N₂O₃255.0770); H NMR

(DMSO-d₆, 500 MHz): and ¹³C NMR (DMSO-d₆,

125 MHz), see table 1.

2.3. Extraction and isolation

9,10-dimethoxycanthin-6-one (2): Yellow

powder, C₁₆H₁₂N₂O₃; ESI-MS (m/z): 280.9 [M+H]⁺;

¹H NMR (CDCl₃, 500 MHz), δ_H(ppm), J (Hz): 8.78

(1H, J = 5.0, H-2), 8.22 (1H, s, H-8), 8.00 (1H, d, J

= 10.0, H-4), 7.85 (1H, d, J = 5.0, H-1), 7.49 (1H, s,

H-11), 6.95 (1H, d, J = 10.0, H-5), 4.08 (3H, s,

OCH₃-9), 4.04 (3H, s, OCH₃-10). ¹³C NMR (CDCl₃,

125 MHz), δ_C(ppm): 159.63 (C-6), 152.35 (C-9),

148.08 (C-10), 145.83 (C-2), 139.71 (C-4), 135.80

(C-16), 134.67 (C-13), 130.68 (C-14), 128.63 (C-5),

116.46 (C-12), 104.18 (C-11), 100.36 (C-8), 56.62

(OCH₃-9), 56.46 (OCH₃-10).

- Isolation of alkaloid compounds:

The dried powder of the roots of Eurycoma

longifolia (1.0 kg) was boilt in water (2.5 l) at 70 ^oC

for 3x5h. The solutions were combined, filtered and

removed water under reduced presssure to obtain the

residue (40 g). The water extract (40 g) was

chromatographed on a Dianion HP-20 column,

eluting with MeOH in H₂O (20; 50; 80 and 100 %,

respectively) to obtain 15 fractions (Fr.1-15).

Fraction Fr.8 (1.7 g) was chromatographed on a

silica gel column, eluting with a gradient of

DCM/MeOH (98:2, 95:5, 9:1, 8:2, 1:1, v/v) to give

19 fractions (Fr.8.1-Fr.8.19). Fr.8.12 was subjected

to a RP-18 column (MeOH/H₂O 7:3) to afford 7

fractions (Fr.8.12A-H). Compound 1 (5.0 mg) and 3

(10 mg) were obtained from Fr.8.12C using a

Sephadex column (100 % MeOH). Fraction Fr.3 (17

g) was separated by silica gel CC, eluting with

DCM/MeOH (98/2, v/v) to afford 15 subfractions

(Fr.3.1-15). Fraction Fr.3.2 was subjected to a silica

gel column (DCM/MeOH 95:5) followed by

Sephadex column (100 % MeOH) to afford

compound 2 (20 mg). Compound 4 (4 mg) was

purified from Fr. 3.6 (120 mg) by column

chromatography on silica gel (DCM/MeOH 95:5)

and Sephadex LH-20 column (MeOH 100 %).

β-carboline-1-propionic acid (3): White

powder, C₁₄H₁₂N₂O₂; ESI-MS (m/z): 238.8 [M-H]^-,

543.0 [M+Na]⁺; ¹H NMR (DMSO-d₆, 500 MHz) and

¹³C NMR (DMSO-d₆, 125 MHz), see table 1.

Infractine (4): Yellow powder, C₁₅H₁₄N₂O₂;

ESI-MS (m/z): 254.9 [M+H]⁺; H NMR (CD₃OD,

500 MHz) and ¹³C NMR (CD₃OD, 125 MHz), see

table 1.

Eurylene (5): White crystal, C₃₄H₅₈O₈; ESI-MS

(m/z): 577.1 [M-H₂O+H]⁺, 559.2 [M-2H₂O+H]⁺;

629.2 [M+Cl]^-; H NMR (CDCl₃, 500 MHz), δ_H

(ppm), J (Hz): 5.10 (2H, t, J = 6.0, H-3, H-22), 4.86

(2H, t, J = 10.0, H-11, 14), 3.76 (1H, dd, J = 8.0,

7.0, H-18), 3.70 (1H, dd, J = 9.5, 5.5, H-7), 2.07

(3H, s, H-32), 2.06 (3H, s, H-34), 2.06-2.04 (2H, m,

H-21, H-4), 1.96 (2H, m, H-16), 1.90 (2H, m, H-9),

1.83 (2H, m, H-17, H-8), 1.68 (6H, s, H-30, H-25),

1.61 (6H, s, H-24, H-1), 1.66-1.48 (4H, m, H-12, H-

13), 1.48-1.37 (4H, m, H-20, H-5), 1.18 (3H, s, H-

29), 1.16 (6H, s, H-26, H-28), 1.15 (3H, s, H-27).

¹³C NMR (CD₃OD, 125 MHz), δ_C(ppm): 17.61 (C-

1, C-24), 21.09 (C-34), 21.15 (C-32), 22.11 (C-4,

21), 22.49 (C-28), 22.76 (C-27), 24.01 (C-26), 24.14

- Isolation of non-ankaloid compounds:

The dried powder of the roots of Eurycoma

longifolia (2 kg) was extracted with EtOH/H₂O

(3x3h) at 50 C. The solvent was evaporated to

afford the EtOH extract (150 g) which was then

added water and successively extracted with n-

hexane and ethyl acetate. The solvent was removed

Vietnam Journal of Chemistry

Phytochemical investigation of E. longifolia…

(C-29), 25.55 (C-17), 25.64 (C-30), 25.66 (C-25), 6), 7.53 (1H, ddd, J = 8.0, 6.8, 1.0, H-7), 7.59 (1H,

25.73 (C-8), 26.85 (C-12), 27.04 (C-13), 34.18 (C- d, J = 8.0, H-8), together with two methylene groups

9), 34.87 (C-16), 37.31 (C-20), 37.58 (C-5), 72.03 at δ_H2.87 (1H, t, J = 7.5, H-1’) and 3.35 (1H, t, J =

(C-6), 72.72 (C-19), 77.62 (C-11), 78.13 (C-14), 7.5, H-2’). The ¹³C NMR spectrum of 3 indicated 14

83.60 (C-10), 83.82 (C-15), 84.38 (C-7), 86.60 (C- carbons including one carboxylic acid at δ_C174.10

18), 124.51 (C-22), 124.52 (C-3), 131,57 (C-23), (C-3’), 11 aromatic carbons at δ_C112.79-144.04,

131.58 (C-2), 170.81 (C-33), 170.94 (C-31).

two methylene carbons at δ_C31.31 (C-1’), and 28.04

Eurycomanone (6): White powder, C₂₀H₂₄O₉; (C-2’). Analysis of MS, ¹H and ¹³C NMR spectra of

ESI-MS (m/z): 408.9 [M+H]⁺; 309.9 [M-H₂O+H]⁺, 3 revealed that this compound was a β-carboline-

406.8 [M-H]^-; H NMR (DMSO-d₆, 500 MHz), δ_Hderivative with propionic acid unit substituted at C-

(ppm), J (Hz): 8.19 (1H, s, OH), 5.98 (1H, brs, H-7), 1. By comparing the NMR data of 3 with those

5.64 (1H, s, H-15), 5.37 (1H, brs, H-21a), 5.20 (2H, reported in the literatures,^[8]compound 3 was

brs, H-21b and H-3), 4.59 (1H, brs, H-1), 4.34 (1H, identified as β-carboline-1-propionic acid. This

brs, H-12), 3.67 (1H, d, J = 8.5, H-20a), 3.53 (1H, d, compound was isolated previously from E.

J = 8.5, H-20b), 2.93 (1H, s, H-9), 2.50 (1H, m, H- longifolia.

5), 2.11 (1H, m, H-6a), 1.97 (1H, m, H-6b), 1.93

Compound 1 was isolated as yellow powder. Its

(3H, s, H-19), 1.05 (3H, s, H-18). ¹³C NMR molecular formular (C₁₄H₁₂N₂O₃) contained one

(DMSO-d₆, 125 MHz), δ_C(ppm): 197.10 (C-2), oxygen atom more than 3, which was establishing

172.33 (C-16), 162.62 (C-4), 146.07 (C-13), 124.79 from molecular ion peak at m/z 255.0775 [M-H]^-

(C-3), 118.70 (C-21), 107.80 (C-11), 82.38 (C-1), (calculated for C₁₄H₁₁N₂O₃255.0770) in HR-ESIMS

79.12 (C-12), 77.96 (C-14), 74.66 (C-15), 70.44 (C- spectrum. The ¹³C NMR data of 1 showed the

7), 66.09 (C-20), 51.17 (C-8), 46.08 (C-9), 44.77 (C- signals similar to those of 3, except some much

10), 40.72 (C-5), 24.61 (C-6), 22.31 (C-18), 9.52 (C- downfield chemical shifts (3-4 ppm) of some carbon

19).

signals at δ_C147.11 (C-1), 36.65 (C-1’), 31.26 (C-

14,15-β-hydroxyklaineanol (7): White powder, 2’) and 177.87 (C-3’, COOH) (table 1). Besides, the

C₂₀H₂₄O₉; ESI-MS (m/z): 433.0 [M+Cl]^-; H NMR signals of aromatic protons of 1 also shifted to

(DMSO-d₆, 500 MHz), δ_H(ppm), J (Hz): 5.16 (1H, downfield (δ_H8.00-9.00 ppm), comparing with those

d, J = 4.0, H-7), 4.54 (1H, brs like triplet, H-11), in compound 3 (table 1). This was due to the effect

4.42 (1H, s, OH), 4.28 (1H, d, J = 9.8, H-1), 4.27 of the N-oxide group. The analysis of MS, H and

(1H, s, OH), 3.48 (1H, m, H-2), 3.45 (1H, brs, H- ¹³C NMR spectra of 1 revealed that this compound

15), 3.12 (1H, dd, J = 9.5, 2.5, H-12), 2.63 (1H, dd, was a β-carboline-N-oxide derivative with an unit of

J = 15.0, 4.0, H-6a), 2.42 (1H, brs, J = 15.0, H-6b), propionic acid substituted at C-1. The structure of 1

2.17 (1H, dd, J = 7.5, 3.0, H-13), 2.11 (1H, m, H- was further confirmed by HSQC and HMBC

3a), 1.96 (1H, dd, J = 17.5, 10.5, H-3b), 1.58 (3H, s, spectra. The HMBC correlation between H-3 (δ_H

H-20), 1.51 (1H, d, J = 2.0, H-9), 1.41 (3H, s, H-19), 9.00)/ C-1 (δ_C147.11), C-4 (δ_C112.39), H-5 (δ_H

1.37 (3H, s, H-18), 1.05 (3H, d, J = 7.0, H-21). C 8.97)/C- 6 (δ_C127.45), C-10 (δ_C126.91, H-4 (δ_H

NMR (DMSO-d₆, 125 MHz), δ_C(ppm): 174.48 (C- 8.68)/C-11 (δ_C121.12), H-6 (δ_H8.28)/C-5 (δ_C

16), 130.87 (C-5), 123.52 (C-4), 81.56 (C-1), 81.36 118.80), C-7 (δ_C121.46) proved the structure of the

(C-12), 76.01 (C-14), 75.78 (C-15), 72.51 (C-11), aromatic ring of β-carboline. Morever, the

69.09 (C-7), 66.43 (C-2), 45.82 (C-8), 45.35 (C-9), correlation of H-1’ (δ_H3.36), H-2’ (δ_H4.18)/C-1 (δ_C

43.05 (C-10), 39.94 (C-13), 27.37 (C-6), 19.33 (C- 147.11), C-3’ (δ_C177.87) confirmed the attachment

20), 18.91 (C-18), 17.26 (C-19), 13.21 (C-21).

of a propionic acid group to C-1. From all evidences

above and by comparison with compound 3,^[7]it is

concluded that compound 1 is β-carboline-2N-oxide-

1-propionic acid (figure 1). As the best of our

3. RESULTS AND DISCUSSION

Compound 3 was isolated as white powder. The knowledge, this is the first time compound 1 has

ESI-MS spectrum of 3 indicated molecular ion peaks been isolated from nature. This compound was

at ESI-MS (m/z) 238.8 [M-H]^-and 543.0 [M+Na]⁺. synthesized from β-carboline-1-propionic acid and

This compound showed the positive Dragendorff commercially available. However, the NMR data of

test, suggesting that 3 was an alkaloid. Its ¹H and ¹³C this compound has not yet been reported. Herein, we

NMR spectra displayed the signals characteristic for report the full NMR data of β-carboline-2N-oxide-1-

a β-carboline alkaloid. The H NMR spectrum of 3 propionic acid.

showed the signals of six aromatic protons at δ_H8.23

Compound 4 was obtained as yellow powder. Its

(1H, d, J = 5.5, H-3), 7.94 (1H, d, J = 5.5, H-4), 8.19 NMR spectral data displayed the signals similar to

(1H, d, J = 8.0, H-5), 7.23 (1H, dd, J = 8.0, 1.5, H- those of 3, except the signals for a methyl ester

Vietnam Journal of Chemistry

Tran Thi Phuong Thao et al.

group appeared at δ_H/δ_C3.67 (3H, s)/49.85 Thus, the structure of 4 was determined as infractine

(COOCH₃) and at δ_C175.00 (COO). This was by comparing its spectral data (table 1) with those

further confirmed by ESI-MS spectrum with a reported in the literature.^[9]This compound has been

molecular ion peak obtained at m/z 254.9 [M+H]⁺isolated for the first time from E. longifolia.

Table 1: H and ¹³C NMR of compounds 1, 3 and 4

Position

δ_H(ppm)

δ_C(ppm)

δ_H(ppm)

δ_C(ppm)

δ_H(ppm)

δ_C(ppm)

147.11

137.19

112.39

118.80

144.04 -

142.62

138.25

114.41

120.79

9.00 (d, J = 5.0)

8.68 (d, J = 5.0)

8.97 (d, J = 8.0)

8.23 (d, J = 5.5)

7.94 (d, J = 5.5)

8.19 (d, J = 8.0)

137.30 8.22 (d, J = 5.5)

112.79 7.95 (d, J = 5.5)

119.17 8.17 (dd,

J = 8.0, 0.5)

8.28 (ddd, J = 8.0,

6.0, 1.0)

8.00 (ddd, J = 8.0,

6.0, 1.0)

127.45 7.23 (dd, J = 8.0, 1.5) 127.80 7.27 (ddd,

J = 7.0, 6.0, 1.0)

121.61 7.56 (ddd,

J = 7.0, 6.5, 1.0)

111.91 7.62 (dd,

J = 8.0, 0.5)

140.35 -

129.50

122.62

112.89

121.46

112.15

7.53 (ddd, J = 8.0,

6.8, 1.0)

7.59 (d, J = 8.0)

8.41 (d, J = 8.0)

1’

2’

3’

140.48

126.91

121.12

134.46

36.65

144.94

122.65

130.32

135.91

33.44

29.49

175.00

49.85

127.01 -

119.01 -

133.99 -

3.36 (t, J = 7.5)

4.18 (t, J = 7.5)

2.87 (t, J = 7.5)

3.35 (t, J = 7.5)

31.31 2.94 (t, J = 7.5)

28.04 3.47 (t, J = 7.5)

174.10 -

31.26

177.87

COOCH₃

3.67 (s, 3H)

^aDMSO-d6, 500 MHz, ^bDMSO-d6, 125 MHz, ^cCD₃OD, 500 MHz, ^dCD₃OD, 125 MHz.

Figure 1: The isolated compounds from the roots of Eurycoma longifolia

Vietnam Journal of Chemistry

Phytochemical investigation of E. longifolia…

Compound 2 was isolated as yellow powder. silimar to those of 6, except some following points:

The ESI-MS of 2 showed a molecular ion peak at the conjugated carbonyl carbon was absent, a methyl

m/z 280.9 [M+H]⁺. Its H NMR data showed the doublet at δ_H/δ_C1.05/18.91 and a methylene group at

signals of two methoxy group substituted to δ_H2.11 (1H, m, H-3a), 1.96 (1H, dd, J = 17.5, 10.5,

aromatic ring at δ_H4.08 (3H, s, OMe-9) and 4.04 H-3b) was assigned to H-21 and H-3, respectively.

(3H, s, OMe-10), together with six aromatic protons Besides, instead of a hemiacetal in C-ring, the

at δ_H8.78 (1H, J = 5.0, H-2), 8.22 (1H, s, H-8), 8.00 signals at δ_H/δ_C1.58 (3H, s)/19.33 and 4.54 (brs, like

(1H, d, J = 10.0, H-4), 7.85 (1H, d, J = 5.0, H-1), t)/72.51 were assigned for C-20 and C-11,

7.49 (1H, s, H-11) and 6.95 (1H, d, J = 10.0, H-5). respectively. By comparison of NMR spectral with

The C NMR of 2 indicated the signals of sixteen those reported in the literature,^[14]compound 7 was

carbons, including 2 methoxy carbons, 6 aromatic determined as 14,15-β-hydroxyklaineanol.

methine carbons, 7 tertiary carbons and a carbonyl

Compound 5 was isolated as yellow powder. Its

amide at δ_C159.6. Based on the above spectral data ESI-MS showed ion molecular peaks at m/z 577.1

and comparison with those in the literature,^[10][M-H₂O+H]⁺, 559.2 [M-2H₂O+H]⁺; 629.2 [M+Cl]^-.

compound

was

elucidated

9,10- The NMR spectra of 5 showed the signal

dimethoxycanthin-6-one. This compound showed characteristic for a squalene triterpene. The ¹³C

the cytotoxic activity against Fibrosarcoma HT-1080 NMR spectrum of 5 displayed 34 carbon signals,

cancer cell line.^[11]

including two carbonyl carbons at δ_C170.94 (C-31)

Compound 6 was obtained as white powder. Its and 170.81 (C-33), four olefin carbons at δ_C131.58

ESI-MS spectrum showed molecular ion peaks at (C-2), 131.57 (C-23), 124.52 (C-3), 124.51 (C-22),

m/z 408.9 [M+H]⁺and 406.8 [M-H]^-. The NMR four oximethines at δ_C86.60, 84.38, 78.13, 77.62,

spectra of 6 dispalyed the signal characteristic for a four tertiary oxygenated carbons at δ_C83.82, 83.60,

quassinoid structure. The ¹H NMR of 6 appeared the 72.72, 72.03, ten methylene carbons at δ_C45.83-

signals of two methyl singlets at δ_H1.93 (3H, s, H- 22.11, together with 10 methyl carbons at δ_C25.66-

19) and 1.05 (3H, s, H-18), one exomethylene group 17.61. However, the intergram in ¹H NMR showed a

and one olefin proton at δ_H5.37 (1H, brs, H-21a), half of total protons calculating by ¹³C NMR and

5.20 (2H, brs, H-21b and H-3), two methylene MS spectra. This indicated a symetry in the structure

groups at δ_H3.67 (1H, d, J = 8.5, H-20a), 3.53 (1H, feature of compound 5. The ¹H NMR of compound 5

d, J = 8.5, H-20b) and 2.11 (1H, m, H-6a), 1.97 (1H, displayed the signals of proton olefin at δ_H5.10 (t, J

m, H-6b). Besides, the signals of four oxymethine = 6.0, H-3 and H-22), 4.86 (t, J = 10.0, H-11 and H-

protons were also observed at δ_H5.98 (1H, brs, H-7), 14), two proton oxymethines at δ_H3.76 (dd, J = 8.0,

5.64 (1H, s, H-15), 4.59 (1H, brs, H-1) and 4.34 (1H, 7.0, H-18) and 3,70 (dd, J = 9.5, 5.5, H-7), two

brs, H-12). The other methine protons were methyl acetates (COCH₃) at δ_H2.07 and 2.06, four

resonated at δ_H2.93 (1H, s, H-9) and 2.50 (1H, m, vinyl methyl at δ_H1.68 (s, H-25 and H-30), 1.61 (s,

H-5). The C NMR of 6 showed the signals of 20 H-1 and H-24), together with other methyl singlet at

carbons, including four olefin carbons, two carbonyl δ_H1.18 (3H, s, H-29), 1.16 (6H, s, H-26 và H-28),

carbons [one δ-lactone carbon at δ_C172.33 (C-16) 1.15 (3H, s, H-27) and methylene protons at δ_H2.04-

and one conjugated ketone carbon at δ_C197.10 (C- 1.28. The assignment of all protons and carbons was

2)], four oximethine carbons, oneoxymethylene, one deduced by analysis of HSQC and HMBC spectra.

hemiacetal carbon at δ_C107.80 (C-11), one tertiary In HMBC spectrum, the correlation between H-11,

oxygenated carbon at δ_C77.96 (C-14), two methyl H-14 (δ_H4.86) and H-32, H-34 (δ_H2.07 and 2.06)/C-

carbons at δ_C9.59 (C-19) and 22.31 (C-18), together 31 (δ_C170.94) and C-33 (δ_C170.81) confirmed the

with other two tertiary carbons, two methine and one location of the acetate group at C-11 and C-14. The

methylene carbons at δ_C51.17-24.61. By comparison correlation between H-3, H-22 (δ_H5.10)/C-1, C-24

of MS and NMR data with those reported in the (δ_C17.61) and C-25, C-30 (δ_C25.66 and 25.64,

literature,^[12]compound 6 was determined as respectively) indicated the position of the double

eurycomanone. Eurycomanone was known as one of bonds. The methyl groups C-27 and C-28 was

the main component contributing the bitte taste of E. determined to be attached to the tetrahydrofuran ring

longifolia. It was also reported that eurycomanone at C-10 and C-15 by the observation of the

enhanced the testosterone level in male rats.^[13]

correlation between H-27 (δ_H1.15)/C-9 (δ_C34.18)

Compound 7 was isolated as a white powder. and H-28 (δ_H1.16)/C-16 (δ_C34.87). The positions of

The NMR spectral data of 7 showed the signals of a the tertiary oxygenated carbons C-6 and C-19 were

klaineanone quassinoid compound. An ion confirmed by the HMBC correlations between H-7

molecular peak was observed at m/z 433.0 [M+Cl]^-(δ_H3.76) and H-18 (δ_H3.70)/C-26 (δ_C24.14) and C-

in its ESI-MS spectrum. The ¹³C NMR of 7 was 29 (δ_C24.01), respectivey. Based on the above

Vietnam Journal of Chemistry

Tran Thi Phuong Thao et al.

453-455.

analysis and comparison of NMR data of 5 with

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Quin, X. P. Lai, Z. R. Su, Z. X. Lin. Seven alkaloids

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backbone 2,5-trans and 2,5-cis-tetrahydrofuran

units.

9. W. Steglich, L. Kopanski, M. Wolf, M. Moser, G.

Tegtmayer. Indol alkaloide aus dem Blaetterpilz

Cortinarius infractus (Agaricales), Tetrahedron Lett.,

1984, 25(22), 2341-2344.

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Corresponding author: Tran Thi Phuong Thao

Institute of Chemistry, Vietnam Academy of Science and Technology

18, Hoang Quoc Viet, Cau Giay district, Hanoi 10000, Viet Nam

E-mail: ntuelam2010@gmail.com

Tel: +84- 2437562094.

6 trang yennguyen 18/04/2022 1140

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