Flavonoids and Alkaloids from Marine-Derived Actinomycete Streptomyces sp. C011

Cite this paper: Vietnam J. Chem., 2020, 58(5), 610-614 Article 
DOI: 10.1002/vjch.202000046 
610 Wiley Online Library © 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH 
Flavonoids and Alkaloids from Marine-Derived Actinomycete 
Streptomyces sp. C011 
Tran Thi Thanh Hoa
1,2
, Vu Van Nam
1
, Doan Thi Mai Huong
1,3*
, Phi Thi Dao
1
, Nguyen Nam Phuong
4
, 
Le Thi Hong Minh
1
, Vu Thi Quyen
1
, Nguyen Mai Anh
1
, Brian T. Murphy
5
, Ho Thi Minh Ly
2
, 
Pham Van Cuong
1,3* 
1
Institute of Marine Biochemistry, Vietnam Academy of Science and Technology, 
18 Hoang Quoc Viet, Cau Giay district, Hanoi 10000, Viet Nam 
2
National Institute of Hygiene and Epidemiology, 1 Yersin, Hai Ba Trung district, Hanoi 10000, Viet Nam 
3
Graduate University of Science and Technology, Vietnam Academy of Science and Technology, 
18 Hoang Quoc Viet, Cau Giay district, Hanoi 10000, Viet Nam 
4
Hanoi Amsterdam High School for the gifted, Hoang Minh Giam, Cau Giay district, Hanoi 10000, Viet Nam 
5
Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, 
1200 West Harrison St., IL 60607, USA 
Submitted March 26, 2020; Accepted April 19, 2020 
Abstract 
Five secondary metabolites including three flavonoids, 6-lavandulyl-5,7,2′,4′-tetrahydroxyflavanone (1), 5′-
lavandulyl-2′-methoxy-2,4,4′,6′-tetrahydroxychalcone (2), 6-lavandulyl-7-methoxy-5,2′,4′-trihydroxyflavanone (3), and 
two alkaloids, tryptoline (4), and norharman (5) were isolated from the culture broth of Streptomyces sp. C011. Their 
structures were determined by spectral data analysis, including MS, 2D NMR, and CD spectrum. All the separated 
compounds were evaluated for their antimicrobial activities. Compounds 1, 2, 3 and 5 exhibited antimicrobial activity. 
Keywords. Streptomyces, marine microorganism, actinomycetes, flavonoid, alkaloid. 
1. INTRODUCTION 
Streptomyces comprises over of 500 described 
species, and belongs to the Streptomycetaceae 
family.
[1-2]
 The genus Streptomyces is the largest 
source of bioactive secondary metabolites , such as 
antitumorals, antivirals, antifungals, 
immunosuppressants, anti-hypertensives, and 
antibiotics.
[3-5]
During our screening program, the ethyl acetate 
extract of Streptomyces sp. C011 exhibited 
antimicrobial activity against a gram-positive (E. 
faecalis ATCC29212, S. aureus ATCC25923, B. 
cereus ATCC13245) bacteria strain and a fungus 
strain (C. albicans ATCC10231) with a MIC value 
of 64, 128, 64, 32 μg/mL, respectively. In this paper, 
we reported the isolation and structural elucidation 
of five compound, 6-lavandulyl-5,7,2′,4′-
tetrahydroxy flavanone (1), 5′-lavandulyl-2′-
methoxy-2,4,4′,6′-tetrahydroxychalcone (2), 6-
lavandulyl-7-methoxy-5,2′,4′-trihydroxyflavanone 
(3), tryptoline (4), and norharman (5) from the 
extract of the culture broth of Streptomyces sp. 
C011. 
Figure 1: Compounds 1-5 isolated from 
Streptomyces sp. C011 
2. MATERIALS AND METHODS 
2.1. General Experimental Procedures 
Optical rotations were recorded on a Polax-2L 
Vietnam Journal of Chemistry Doan Thi Mai Huong et al. 
© 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 611 
polarimeter in MeOH. CD spectra were measured on 
a Chirascan CD spectrometer. HR-ESI-MS spectra 
were obtained using an Agilent 6550 iFunnel Q-TOF 
LC/MS system. The ESI-MS were recorded on an 
Agilent 1100 LC-MSD Trap spectrometer. All NMR 
spectra were recorder on a Bruker 500 MHz 
instrument (Avance 500). TLC silica gel Merck 60 
F254 was used as thin-layer chromatography. Column 
chromatography (CC) was performed on silica-gel 
(Kieselgel 60) or Sephadex LH-20. 
2.2. Marine materials 
Streptomyces sp. C011 was isolated from a marine 
crinoid in the sea of Van Phong (Khanh Hoa, 
Vietnam) in December 2016 and was identified by 
Prof. Do Cong Thung of Institute of Marine 
Environment and Resources - Vietnam Academy of 
Science and Technology (VAST). Voucher 
specimens were deposited at the Institute of Marine 
Environment and Resources, Hai Phong, Vietnam. 
The strain C011 was identified belonging to the 
genus Streptomyces by using 16S rRNA gene 
sequence analysis. Strain C011 was cultured in 50 L 
of high-nutrient medium A1+ (yeast extract: 4 g/L; 
peptone: 2 g/L; soluble starch: 10 g/L; instant ocean: 
30 g/L; CaCO3: 1 g/L; pH 7.0) for 10 days at 28 °C 
while shaking at 150 rpm. 
2.3. Extraction and isolation 
The culture broth (50 L) of Streptomyces sp. C011 
strain was filtered. Then this culture solution was 
subjected to amberlite-XAD 16 column (Ø 10) and 
eluted with 40 L of MeOH, combined with 
concentration under reduced pressure to obtain 
methanol residue (C011, 172 g). The extract C011 
was chromatographed on a Dianion column, eluting 
with MeOH/H2O (0/100→100/0, v/v) to provide 
eight fractions, F1-F8. 
Fraction F2 (17.0 g) was chromatographed on a 
silica gel column eluting with a gradient of 
dichloromethane/acetone (100/0→50/50, v/v) to 
give six sub-fractions, F2.1–F2.6. Sub-fraction F2.2 
(0.48 g) was chromatographed on a Sephadex LH-20 
column using MeOH to give 5 sub-subfraction, 
F2.2.1-F2.2.5. Compound 1 (2.5 mg) and 2 (2.1 mg) 
were obtained from F2.2.2 on a silica gel column 
eluting with CH2Cl2/EtOAc (100/0→0/100, v/v). 
Sub-fraction F2.4 (0.6 g) was chromatographed on a 
Sephadex LH-20 column eluting with MeOH to 
yield compound 4 (3.2 mg). Fraction F4 (7.0 g) was 
chromatographed on a silica gel column eluting with 
CH2Cl2/acetone (100/0→0/100, v/v) to obtain four 
sub-fractions, F4.1-F4.4. Sub-fraction F4.3 was 
chromatographed on Sephadex LH-20 column 
eluting with MeOH to obtain compound 3 (1.7 mg). 
Fraction F5 (12.0 g) was subjected to CC on 
silica gel, eluted with CH2Cl2/acetone gradient to 
obtain five sub-fractions, F5.1-F5.5. The purification 
of the sub-fraction F5.5 was ...  m, H-2′′), 2.63 (2H, d, J = 
8.0 Hz, H-1′′), 3.89 (3H, s, OCH3), 4.57 (1H, d, J = 
2.5 Hz, Ha-9′′), 4.61 (1H, m, Hb-9′′), 5.06 (1H, t, J = 
6.5 Hz, H-4′′), 5.97 (1H, s, H-3′), 6.31 (1H, m, H-5), 
6.33 (1H, d, J = 2.0 Hz, H-3), 7.39 (1H, d, J = 8.5 
Hz, H-6), 7.94 (1H, d, J = 15.5 Hz, H-α), 8.02 (1H, 
d, J = 15.5 Hz, H-β). 13C-NMR (CD3OD, 125 MHz) 
δC (ppm): 17.88 (C-6′′), 19.05 (C-10′′), 25.91 (C-
7′′), 28.15 (C-1′′), 32.43 (C-3′′), 48.01 (C-2′′), 56.05 
(OCH3), 91.59 (C-3′), 103.67 (C-3), 106.51 (C-1′), 
108.85 (C-5′), 108.96 (C-5), 111.13 (C-9′′), 116.25 
(C-1), 125.04 (C-4′′), 125.42 (C-α), 131.56 (C-6), 
131.77 (C-5′′), 139.77 (C-β), 149.86 (C-8′′), 160.31 
(C-2), 162.26 (C-4), 162.43 (C-4′), 164.08 (C-2′), 
166.63 (C-6′), 194.75 (C-γ). 
6-lavandulyl-7-methoxy-5,2′,4′-
trihydroxyflavanone (3): White solid, [α]D
27 
= -28.3 
(c 0.8, MeOH). HR-ESI-MS: m/z 439.2115 [M+H]
+ 
Vietnam Journal of Chemistry Flavonoids and alkaloids from 
© 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 612 
(Calcd. for [C26H31O6]
+
, 439,2121).
 1
H-NMR 
(CD3OD, 500 MHz) δH (ppm): 1.49 (3H, s, H-12), 
1.58 (3H, s, H-13), 1.65 (3H, s, H-16), 2.04 (2H, m, 
H-9), 2.51 (1H, m, H-8), 2.63 (1H, d, J = 5.5 Hz, Ha-
7), 2.65 (1H, d, J = 5.5 Hz, Hb-7), 3.82 (3H, s, 
-OCH3), 4.54 (1H, d, J = 2.5 Hz, Ha-15), 4.59 (1H, 
dd, J = 1.5, 2.5 Hz, Hb-15), 4.98 (1H, t, J = 7.0 Hz, 
H-10), 6.11 (1H, s, H-5), 6.35 (1H, d, m, H-3′), 6.37 
(1H, m, H-5′), 7.32 (1H, d, J = 8.5 Hz, H-6′). 13C-
NMR (CD3OD, 125 MHz) δC (ppm): 17.82 (C-6′′), 
19.18 (C-10′′), 25.85 (C-7′′), 28.19 (C-1′′), 32.37 (C-
3′′), 48.20 (C-3, C-2′′), 55.92 (-OCH3), 75.46 (C-2), 
93.35 (C-8), 103.39 (C-3′), 105.74 (C-10), 107.64 
(C-5′), 109.57 (C-6), 111.15 (C-9′′), 118.48 (C-1′), 
124.81 (C-4′′), 128.48 (C-6′), 132.02 (C-5′′), 149.78 
(C-8′′), 156.64 (C-2′), 159.46 (C-4′), 161.86 (C-7), 
164.86 (C-5), 164.86 (C-9), 193.89 (C=O). 
Tryptoline (4): White solid, mp. 204-205 
o
C. 
ESI-MS: m/z 173 [M+H]
+
. 
1
H-NMR (CD3OD) δH 
(ppm): 2.78 (2H, t, J = 5.5 Hz, H-4), 3.15 (2H, t, J = 
5.5 Hz, H-3), 6.96 (1H, ddd, J = 1.0, 8.0, 9.0 Hz, H-
6), 3.99 (2H, s, H-1), 7.05 (1H, ddd, J = 1.5, 7.5, 9.0 
Hz, H-7), 7.27 (1H, dd, J = 1.0, 8.0 Hz, H-8), 7.40 
(1H, d, J = 7.5 Hz, H-5). 
13
C-NMR (125 MHz, 
CD3OD) δC (ppm): 22.72 (C-4), 43.51 (C-1), 44.59 
(C-3), 108.28 (C-4a), 111.71 (C-5), 118.33 (C-8), 
119.58 (C-6), 121.86 (C-7), 128.74 (C-4b), 133.31 
(C-9a), 137.66 (C-8a). 
Norharman (5): White solid, mp. 198-200 
o
C; 
ESI-MS: m/z 169 [M+H]
+
. 
1
H-NMR (500 MHz, 
CD3OD) δH (ppm): 7.29 (1H, dd, J = 2.5, 8.0 Hz, H-
6), 7.58 (1H, dd, J = 0.5, 8.5 Hz, H-7), 7.59 (1H, d, J 
= 8.5 Hz, H-8), 8.11 (1H, d, J = 5.5 Hz, H-4), 8.21 
(1H, d, J = 8.0 Hz, H-5), 8.31 (1H, d, J = 5.5 Hz, H-
3), 8.81 (1H, s, H-1). 
13
C-NMR (125 MHz, CD3OD) 
δC (ppm): 112.84 (C-8), 116.08 (C-4), 120.85 (C-6), 
122.22 (C-4b), 122.72 (C-5), 129.75 (C-7), 130.46 
(C-4a), 134.11 (C-1), 137.80 (C-9a), 138.42 (C-3), 
142.77 (C-8a). 
3. RESULTS AND DISCUSSION 
Compound 1 was obtained yellow amorphous solid, 
and was optically active [α]D
27
 = +3.1
o
 (c 0.2, 
MeOH). Its molecular formula was determined as 
C25H28O6 by HR-ESI-MS at m/z 425.1960 [M+H]
+
(Calcd. for [C25H29O6]
+
, 425.1964). The 
13
C-NMR, 
DEPT and HSQC spectra of 1 showed the signals of 
25 carbons, including three methyl groups at δC 
17.83 (C-6′′), 19.22 (C-10′′), 25.84 (C-7′′), one 
carbonyl group at δC 198.85 (C-4), four methylene 
groups, two sp
3
 methine groups, five sp
2
 methine 
groups, and ten quaternary carbons. The 1H-NMR 
spectrum of 1 showed the signal of one aromatic 
proton of A ring at δH 5.91 (1H, s, H-8), three ABX 
aromatic protons of B ring at δH 6.36 (1H, dd, J = 
2.0, 8.0 Hz H-5′), 6.38 (1H, d, J = 2.5 Hz, H-3′), 
7.32 (1H, d, J = 8.0 Hz, H-6´), three protons of C 
ring at δH 5.57 (1H, dd, J = 3.0, 13.5 Hz, H-2), 2.74 
(1H, dd, J = 2.5, 17.0 Hz, Ha-3), 2.98 (1H, dd, J = 
13.5, 17.0 Hz, Hb-3) suggested the presence of 
flavanone moiety. In addition, the signal of three 
methyl groups at δH 1.50 (3H, s, H-6′′), 1.59 (3H, s, 
H-7′′), 1.65 (3H, s, H-10′′), one sp2 methylene group 
at δH 4.54 (1H, d, J = 2.0 Hz, Ha-9′′), 4.60 (1H, m, 
Hb-9′′), one olefinic proton at δH 4.99 (1H, m, H-4′′), 
and a number aliphatic protons from 2.02 to 2.98 
ppm were also noted. The 
1
H-
1
H COSY data 
revealed three spin-spin coupling systems: CH2-
1′′/H-2′′/CH2-3′′/H-4′′, H-5′/H-6′, and H-2/CH2-3 
(figure 2). In the HMBC spectrum, cross-peaks of 
H-2′′ with C-8′′, C-9′′, C-10′′, C-4′′, C-6; H-4′′ with 
C-6′′, C-7′′; and those of H-1′′ with C-3′′, C-2′′, C-8′′ 
indicated the lavandulyl group in the structure of 1. 
Futhermore, HMBC corelation of the proton of CH2-
1′′ with C-5, C-6 and C-7 indicated the linkage of 
the lavandulyl group at C-6 (figure 2). A negative 
Cotton effect at 292 nm (Δ -5.9), and a positive 
Cotton effect at 312 nm (Δ +0.9) were observed in 
the CD spectrum of 1 revealing the S-configuration 
for carbon C-2.
[6-8]
 Consequently, the structure of 1 
was elucidated as 6-lavandulyl-5,7,2′,4′-
tetrahydroxyflavanone.
[8-9]
Compound 2 was obtained as an optically active 
[α]27D = -1.9 (c 0.5, CH2Cl2). The HR-ESI-MS data 
exhibited a quasi-molecular ion [M+H]
+ 
at m/z 
439.2117 (Calcd. for [C26H31O6]
+
, 439.2121). Along 
with the 
13
C-NMR data, a molecular formula of 
C26H30O6 was suggested for 2. Comparison of the 
1
H-NMR and 
13
C-NMR spectra with those of 1 
revealed the same substructures, lavandulyl group, A 
ring and B ring systems for compound 2. However, 
the CH=CH system [δH 7.94 (1H, d, J = 15.5 Hz, H-
α), δC 125.42 (C-α); δH 8.02 (1H, d, J = 15.5 Hz, H-
β), δC 139.77 (C-β)] were observed in the 1D-NMR 
of 2 instead of the resonances of the coupling system 
CH-2/CH2-3 in the structure of 1. Three spin-spin 
coupling systems of 2 were established from their 
1
H-
1
H COSY spectrum analysis such as CH2-1′′/H-
2′′/CH2-3′′/H-4′′, H-α/H-β, and H-5/H-6. The 
connection of these systems was established by 
HMBC correlations (figure 2). The HMBC 
correlations between H-β and C-6 (δC 109.57)/C-2 
(δC 160.31)/C-γ (δC 194.75) determined the linkage 
of the C-β with C-1 of A ring. HMBC correlations 
from H-1′′ to C-4′, C-5′ and C-6′, suggested the 
position of lavandulyl group at C-5′. Additionally, 
the positions of the methoxy group at C-2′ were 
defined by HMBC correlations of methoxy protons 
Vietnam Journal of Chemistry Doan Thi Mai Huong et al. 
© 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 613 
with C-2′. Thus, complete analyses of the 2D-NMR 
spectra and comparison with the reported data 
allowed determining the structure of 2 to be 5′-
lavandulyl-2′-methoxy-2,4,4′,6′-
tetrahydroxychalcone.
[7-9] 
Figure 2: The key HMBC and COSY correlations of 
compounds 1 and 2 
Compound 3 was obtained as an optically active 
[α]D
27 
= -28.3 (c 0.8, MeOH). The molecular formula 
of 3 was deduced to be C26H30O6 based on its HR-
ESI-MS at m/z: 439.2115 [M+H]
+
 (Calcd. for 
[C26H31O6]
+
, 439.2121). The 1D-NMR of compound 
3 showed the signals similar of compound 1, except 
for the presence of a methoxy group (δH 3.82, δC 
55.92) in 3. Analyses of the NMR spectra, [α]D, and 
comparison with previously reported literature,
[8-9]
compound 3 was identified as 6-lavandulyl-7-
methoxy-5,2′,4′-trihydroxyflavanone. 
Compound 4 was obtained as white solid, mp. 
204-205 
o
C. The ESI-MS spectrum of 4 showed the 
pseudomolecular ion peak at m/z 173 [M+H]
+
. 
Considering the 
13
C-NMR data, a molecular formula 
of C11H12N2 was suggested for 4. In the 
1
H-NMR 
spectrum, the presence of an 1,2-disubstituted 
benzene ring [δH 7.40 (1H, d, J = 7.5 Hz, H-5), 7.27 
(1H, dd, J = 1.0, 8.0 Hz, H-8), 7.05 (1H, ddd, J = 
1.5, 7.5, 9.0 Hz, H-7), 6.96 (1H, ddd, J = 1.0, 8.0, 
9.0 Hz, H-6)], and the signals of proton at δH from 
2.78 to 3.99 were noted. The 
13
C-NMR and DEPT 
spectra of 4 showed signals of 11 carbons, including 
four methine sp
2 
groups, three
methylene sp
3
 groups 
and four quaternary carbons. The ESI-MS, NMR 
data of 4 was in agreement with that reported for 
tryptoline.
[10] 
Compound 5 was isolated as white solid, mp. 
198-200 
o
C. ESI-MS showed the proton adduct ion 
[M+H]
+ 
at m/z 169. The 
13
C-NMR spectra of 5 
showed signals of 11 cacbon, including seven sp
2 
methine groups and four quaternary carbons. The 
carbon chemical shift of C-1 (δC 134.11), C-9a (δC 
137.80), C-3 (δC 138.42), C-8a (δC 142.77) 
suggested their linkage to nitrogen. The 
1
H-NMR 
spectrum showed the signals of an 1,2-disubstituted 
benzene ring at δH 7.29 (1H, dd, J = 2.5, 8.0 Hz, H-
6), 7.58 (1H, dd, J = 0.5, 8.5 Hz, H-7), 7.59 (1H, d, J 
= 8.5 Hz, H-8), 8.21 (1H, d, J = 8.0 Hz, H-5), and 
three aromatic protons at δH 8.11 (1H, d, J = 5.5 Hz, 
H-4), 8.31 (1H, d, J = 5.5 Hz, H-3), 8.81 (1H, s, 
H-1). Intensive analysis of the 2D-NMR spectra 
defined the structure of 5 as norharman. Its NMR 
data were consistent with those reported in the 
literature.
[11]
All the separated compounds (1-5) were 
evaluated for their antibacterial activity against three 
Gram-positive bacteria (Enterococcus faecalis, 
Staphylococcus aureus, and Bacillus cereus), three 
Gram-negative bacteria (Escherichia coli, 
Pseudomonas aeruginosa and Salmonella enterica), 
and antiyeast property against Candida albicans. 
Compound 1 exhibited antimicrobial activity against 
E. faecalis and S. aureus, B. cereus, P. aeruginosa, S. 
enterica and C. albicans with MIC values of 1 to 8 
µg/mL. Compound 2 showed inhibitory activity 
against Gram-positive, Gram-negative and C. 
albicans with MIC values of 4 to 16 µg/mL. 
Compound 3 showed inhibitory activity for all test 
streams with MIC values of 16 to 128 µg/mL. 
Compound 5 was selectively inhibited S. aureus with 
MIC value of 32 µg/mL while compound 4 provided 
a MIC value greater than 256 µg/mL (table 1). 
Table 1: Antibacterial and antifungal activities of compounds 1-5 (MIC: μg/mL) 
Compounds 
Gram-positive Gram-negative Yeast 
E. 
faecalis 
S. 
aureus 
B. 
cereus 
E. 
coli 
P. 
aeruginosa 
S. 
enterica 
C. 
albicans 
1 1 1 1 >256 1 8 1 
2 8 8 8 4 8 8 16 
3 32 32 16 128 32 32 32 
4 >256 >256 >256 >256 >256 >256 >256 
5 >256 32 >256 >256 >256 >256 >256 
Streptomycin 256 256 128 32 256 128 - 
Cyclohexamide - - - - - - 32 
Vietnam Journal of Chemistry Flavonoids and alkaloids from 
© 2020 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 614 
4. CONCLUSION 
Five secondary metabolites including three 
flavonoids, 6-lavandulyl-5,7,2′,4′-tetrahydroxy 
flavanone (1), 5′-lavandulyl-2′-methoxy-2,4,4′,6′-
tetrahydroxychalcone (2), 6-lavandulyl-7-methoxy-
5,2′,4′-trihydroxyflavanone (3), and two alkaloids, 
tryptoline (4), and norharman (5) were isolated from 
the culture broth of Streptomyces sp. C011. Their 
chemical structures were determined by means of 
spectroscopic methods including 1D, 2D-NMR, MS 
and CD data. 
Acknowledgements. We thank to Prof. Do Cong 
Thung, Institute of Marine Environment and 
Resources for marine sample collection. This 
research was funded by the Fogarty International 
Center of the National Institutes of Health under 
Award Number D43TW010530. 
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Corresponding author: Doan Thi Mai Huong 
Institute of Marine Biochemistry 
Vietnam Academy of Science and Technology 
18, Hoang Quoc Viet, Cau Giay district, Hanoi 10000, Viet Nam 
E-mail: huongdm@imbc.vast.vn, Tel.: +84- 913586631.