Diterpenoids from Rosmarinus officinalis L. and their nitric oxide inhibitory activity

Cite this paper: Vietnam J. Chem., 2021, 59(2), 229-234 Article 
DOI: 10.1002/vjch.202000161 
229 Wiley Online Library © 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH 
Diterpenoids from Rosmarinus officinalis L. and their nitric oxide 
inhibitory activity 
Le Thi Huyen
*
, Le Thi Oanh 
VNU University of Science, Vietnam National University, Hanoi, 
19 Le Thanh Tong, Hoan Kiem, Hanoi 10000, Viet Nam 
Submitted September 17, 2020; Accepted February 4, 2021 
Abstract 
One icetexane diterpenoid, demethylsalvicanol (1) and four abietane diterpenoids, sageone (2), 20-deoxocarnosol 
(3), 11,12,20-trihydroxy-abieta-8,11,13-triene (4), and 7α-ethoxyrosmanol (5) were isolated from the n-hexane layer of 
the leaves and twigs of Rosmarinus officinalis L. Chemical structures of compounds were identified by ESI-MS, 1D-, 
2D-NMR spectra and by comparison of the spectral data in the literature. Compounds 1-5 were evaluated anti-
inflammatory activity by inhibitory NO production, LPS stimulated on RAW 264.7 cells. At a concentration of 100 µM, 
compound 4 exhibited inhibitory percentage of 34.7±1.8 %, meanwhile compounds 1-3 and 5 showed cytotoxic effect. 
After dilution to concentration of 20 µM, except compound 1 and 2, compounds 3-5 did not show cytotoxic effect. 
Their NO inhibitory productions were ranging from 20.5±2.4 % to 26.7±1.9 %. Compounds 1, 3 and 4 have been 
reported for the first time from the Rosmarinus genus. 
Keywords. Rosmarinus officinalis, icetexane diterpenoid, abietane diterpenoid, nitric oxide inhibitor. 
1. INTRODUCTION 
Rosmarinus officinalis L. (family Lamiaceae) is a 
shrub, woody, perennial herbs with fragrant 
evergreen needle-like leaves that found primarily in 
the Mediterranean region and widely spread in 
European, American, and Asian countries.
[1]
 It has 
been used as a herbal medicine since ancient times 
for several diseases. It shows antioxidant,
[2]
 anti-
inflammator,
[3]
 antimicrobial,
[4,5]
 anticancer,
[6-8]
antidiabetic,
[9]
 and hepatoprotective.
[10]
 The main 
components have been identified as diterpenoids, 
triterpenoids, flavonoids, etc.
[11-13]
 However, 
phytochemical study of this plant has not been 
studied yet in Vietnam. This paper reported the 
isolation, structure elucidation and anti-
inflammatory activity of five diterpenoids from the 
n-hexane extract of the leaves and twigs of R. 
officinalis. 
2. MATERIALS AND METHODS 
2.1. Plant materials 
The leaves and twigs of R. officinalis were collected 
in Ha Giang, Vietnam in January 2019, and 
identified by Dr. Nguyen The Cuong, Institute of 
Ecology and Biological Resources, Vietnam 
Academy of Science and Technology). A voucher 
specimen (RO.19.01) was stored at Faculty of 
Chemistry, VNU University of Science. 
2.2. General experimental procedures 
The general experimental procedures and 
measurement techniques are as the same as 
described in Ref. [21]. 
2.3. Extraction and separation 
The dried ground leaves and twigs of R. officinalis 
(2.0 kg) were grinded into fine powder and extracted 
with methanol (3 times 5 L) in ultrasonic extractor 
for 2 h each. After removal of the solvent under 
reduced pressure, the to get the residue was 160.0 
g. Warm water (2 L, 50 
o
C) was added to this extract 
and then successively partitioned by solvents with 
increasing polarity n-hexane, EtOAc to obtain the 
n-hexane (ROH, 36.0 g), EtOAc (ROE, 85.0 g) and 
aqueous layer (ROW, 35.0 g) after evaporating 
solvents in vacuo under reduced pressure to 
dryness. 
Vietnam Journal of Chemistry Le Thi Huyen et al. 
© 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 230 
Figure 1: Chemical structures of compounds 1-5 
The ROH fraction was carried out by a silica gel 
column eluting with a n-hexane increasing amounts 
of EtOAc (100:0 0:1, v/v) to yield fractions H1–
H7. H2 fraction was then separated on a silica gel 
column and eluted with a gradient mobile phase n-
hexane-acetone (100:0 0:1, v/v) to give fractions, 
H2A – H2E. H2A fraction (776.9 mg) was 
chromatographed by an RP-18 column eluting with 
acetone-H2O (2.5:1, v/v) to give fractions, H3A-
H3E. H3C was separated on an RP-18 column 
eluting with acetone- H2O (2.0:1, v/v) which 
afforded compound 2 (3.0 mg). Compounds 3 (10.0 
mg) and 4 (17.6 mg) were obtained from H3D 
fraction using RP-18 column (solvent eluents of 
acetone-H2O, 2.0:1, v/v). H2C fraction (887.0 mg) 
was separated by an RP-18 column using acetone-
H2O (2.0:1, v/v) as mobile phase to obtain fractions, 
H4A-H4C. Fraction H4C was further separated by 
an RP-18 column washing with acetone-H2O (1.5:1, 
v/v) giving 1 (21.0 mg). Fraction H2E (1.725 g) was 
loaded on an RP-18 column eluting with acetone-
H2O (2.5:1, v/v) to give five fractions, H5A-H5E. 
H5C was further purified on RP-18 column, eluted 
with acetone-H2O (2.0:1, v/v), a compound labeled 
as 5 (27.2 mg) was obtained in pure state. 
Demethylsalvicanol (1): Colorless amorphous 
powder; ESI-MS m/z: 319.23 [M+H]
+
, C20H30O3; 
MW: 318; 
1
H- and 
13
C-NMR (CDCl3) data, see table 1. 
Sageone (2): Colorless amorphous powder; ESI-
MS m/z: 301.18 [M+H]
+
, C19H24O3; MW: 300; 
1
H- 
and 
13
C-NMR (CDCl3) data, see table 1. 
20-Deoxocarnosol (3): Colorless amorphous 
powder; ESI-MS m/z: 317.21 [M+H]
+
, C20H28O3; 
MW: 316; 
1
H- and 
13
C-NMR (CDCl3) data, see table 1. 
11,12,20-Trihydroxy-abieta-8,11,13-triene (4): 
Colorless amorphous powder; ESI-MS m/z: 319.22 
[M+H]
+
, C20H30O3; MW: 318; 
1
H- and 
13
C-NMR 
(CDCl3), data, see table 2. 
7α-ethoxyrosmanol (5): Colorless amorphous 
powder; ESI-MS m/z: 375.23 [M+H]
+
, C22H30O5; 
MW: 374; 
1
H- and 
13
C-NMR (CDCl3) data, see 
table 2. 
2.4. Inhibition of nitric oxide production 
Inhibition of NO production in LPS-stimulated 
RAW 264.7 cell assay, see reference  ... lished to be 
demethylsalvicanol, an icetexane diterpenoid previously 
isolated from Salvia broussonetii.
[16]
Compound 2 was obtained as a colorless 
amorphous powder. It had a molecular formula 
C20H28O3 which was suggested from a pseudo-
molecular ion peak [M+H]
+ 
at m/z 317.18 in the ESI-
MS and in consistent with 
13
C NMR data. 
1
H NMR 
and HSQC spectra of 2 also showed the presence of 
two tertiary methyl groups at δH 0.85 and 1.14; each 
3H, s), an isopropyl group at δH 1.24 (d, J = 7.0 Hz), 
1.26 (d, J = 7.0 Hz) and 3.10 (1H, m), an aromatic 
proton signal at δH 6.61 (s), and a pair of doublets at 
δH 3.08 and 4.31 (d, J = 8.5 Hz) was due to H-20. 
The 
13
C NMR spectrum of 2 showed 20 carbon 
resonances coresponding to seven non-protonated 
carbons, four methines, five methylenes, and four 
methyl carbons. Of these, three carbon signals at δC 
21.5, 22.3 and 27.2 were assigned for an isopropyl 
group; six carbon signals ranging from δC 112.5 to 
139.9 together with a singlet aromatic proton signal 
at δH 6.61 suggested of a pentasubtituted aromatic 
ring; two oxygen bearing carbons at δC 68.8 and 
71.7. The NMR data of 2 were similar to the 
corresponding data of 20-deoxocarnosol
[17]
 (Table 
1). In addition, the HMBC correlations between H-
18 (δH 0.85) and C-3 (δC 41.3)/C-4 (δC 34.0)/C-5 (δC 
43.2)/C-19 (δC 21.3) and between H-19 (δH 1.14) 
and C-3/C-4/C-5/C-18 (δC 33.0) confirmed both two 
angular methyl groups at C-4; the HMBC 
correlations from H-16 (δH 1.24)/H-17 (δH 1.26) to 
C-13 (δC 131.9)/C-15 (δC 27.3) and from H-15 (δH 
3.10) to C-12 (δC 141.5)/C-13 (δC 132.8)/C-16 (δC 
21.5)/C-17 (δC 22.3) indicated the location of 
isopropyl group at C-13 of the aromatic ring. The 
NMR data of ring C of 2 with those of 20-
deoxocarnosol were found to match, identifying the 
two hydroxyl groups were at C-11 and C-12 , which 
were further confirmed by the observation of the 
HMBC correlations from H-14 (δH 6.56)/H-15 to C-
12 (δC 140.9). From the above data, compound 2 
was identified to be 20-deoxocarnosol, an abietane 
diterpenoid previously reported from Coleus 
barbatus.
[17]
Compound 3 was isolated as a colorless 
amorphous powder. 
1
H-NMR spectrum of 3 showed 
the presence of four tertiary groups at δH 1.24, 1.23, 
1.27, 1.27 and one aromatic proton at δH 6.58 (s, H-
14). The 
13
C-NMR and HSQC spectra displayed 
signals of 19 carbons, including a ketone group at δC 
202.1 which appeared to be conjugated with a tetra-
substituted olefin (δC 116.5 and 175.6). Therefore, 
the structure of 3 was determined to be sageone, a 
nor-diterpene compound isolated from Salvia 
officinalis.
[18]
Compound 4 was appeared as a white 
amorphous powder. Its ESI-MS had a pseudo-
molecular ion peak at m/z 319.22 [M+H]
+
 together 
with 
13
C NMR analysis which was determined its 
molecular formula of C20H30O3. The 
1
H and 
13
C 
NMR spectra of 4 were quite similar to those of 2 
except for the replacement of an oxygenated methine 
(δH 4.71/δC 71.1) in 2 instead of a methylene group 
(δH 2.85/δC 32.0) in 4. In addition, molecular 
formula of 4 (C20H30O3) had more two hydrogen 
than that of 2 (C20H28O3). These clear findings 
implied that the structure of 4 was similar to 2 
except for the absence of ether bridge between C-7 
and C-20 in compound 4. The remaining NMR 
signals of 4 were assigned by analysis of HSQC and 
HMBC spectra as mentioned in compound 2. From 
above spectral findings and comparison with the 
NMR data of 11,12,20-trihydroxy-abieta-8,11,13-
triene - the compound previously isolated from 
Salvia mellifera,
[19]
 compound 4 was identified as 
11,12,20-trihydroxy-abieta-8,11,13-triene. 
Compound 5 was obtained as an yellow 
amorphous powder. It showed identical signals with 
those of compound 2 except the chemical shift of a 
carbonyl group at δC 129.3 (C-20) and the presence 
of ethoxy group in compound 5 (δC 66.2 and 15.8). 
Comparison of the NMR data of 5 with those 
published in the literatures, 5 was identified as 7α-
ethoxyrosmanol.
[20]
To evaluate NO inhibitory production on RAW 
264.7 cells, LPS-stimulated, all compounds were 
sceened for cytotoxic activity at concentrations of 
100 and 20 µM. All compounds showed cell 
viability over than 80% at the concentration of 20 
µM was further chosen for evaluating NO inhibitory 
production. As the results, compounds 1-5 showed 
weak inhibitory activity inhibitory rates ranging 
from 20.5±2.4 % to 51.6±1.5 %. L-NMMA was 
used as a positive control with NO inhibitory values
Vietnam Journal of Chemistry Le Thi Huyen et al. 
© 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 232 
of 82.2±2.5 % at the concentration of 20 µM. 
Table 1: NMR spectral data of 1-3 and reference compounds 
C 
1 2 3 
#δC
,a
 δC
 a,b
 δH
a,c
 (mult., J in Hz) 
$δC
,a
 δC
 a,b
 δH
a,c
 (mult., J in Hz) 
%δC
,a
 δC
 a,b
 δH
a,c
 (mult., J in Hz) 
1 41.6 41.3 1.50 (m)/1.80 (m) 202.1 202.1 - 30.1 31.1 
2.59 (m) 
2.12 (brd, 13.5) 
2 18.7 18.6 1.41 (m)/1.80 (m) 35.1 35.1 2.69 (dd, 7.0, 12.0) 19.0 19.1 1.62 (m) 
3 42.3 42.3 1.27 (m)/1.40 (m) 35.6 35.7 1.94 (t, 7.0) 41.2 41.3 1.28 (m)/1.56 (m) 
4 34.4 34.4 - 37.2 37.2 - 33.9 34.0 - 
5 58.1 58.2 1.32 (dd, 12.5, 2.5) 175.8 175.6 - 43.0 43.2 
1.46 (ddd, 1.5, 5.5, 
11.5) 
6 24.3 24.3 1.15 (m)/2.00 (m) 27.4 27.4 2.53 (t, 7.5) 30.8 30.2 1.57 (m)/2.03 (m) 
7 
36.0 36.1 2.64 (dd, 12.0, 14.0) 
2.73 (dd, 7.5, 14.0) 
28.4 28.4 2.39 (t, 7.5) 71.1 71.1 4.71 (dd, 1.5, 3.0) 
8 136.4 136.1 - 127.5 127.5 - 132.9 133.3 - 
9 120.3 121.1 - 130.3 130.3 - 127.5 127.6 - 
10 71.3 71.9 - 116.5 116.5 - 39.9 40.1 - 
11 142.6 142.6 - 139.9 140.0 - 140.9 139.0 - 
12 140.4 141.5 - 143.2 143.3 - 139.3 140.9 - 
13 132.4 132.8 - 133.1 133.1 - 132.2 131.9 - 
14 117.5 117.9 6.56 (s) 116.5 116.6 6.58 (s) 112.2 112.5 6.61 (s) 
15 27.2 27.2 3.18 (m) 27.1 27.2 3.29 (m) 27.1 27.3 3.10 (m) 
16 21.5 21.5 1.23 (d, 7.0) 22.4 22.4 1.24 (d, 6.5) 22.7 22.6 1.24 (d, 7.0) 
17 22.3 22.3 1.21 (d, 7.0) 22.4 22.4 1.23 (d, 6.5) 22.7 22.7 1.26 (d, 7.0) 
18 32.2 32.2 0.85 (s) 26.1 26.2 1.27 (s) 32.0 33.0 0.85 (s) 
19 22.8 22.9 0.92 (s) 26.1 26.2 1.27 (s) 21.2 21.3 1.14 (s) 
20 41.6 41.6 2.57 (s)/3.03 (s) 68.5 68.6 
3.08 (d, 8.5)/4.31 (d, 
8.5) 
Measured in 
a)
CDCl3, 
b)
125 MHz, 
c)
500 MHz. 
#)δC of demethylsalvicanol,
[16]
$)δC of sageone
[18]
,
%)δC of 20-deoxocarnosol.
[17]
Figure 2: The key HMBC correlations of compounds 1-5 
Vietnam Journal of Chemistry Diterpenoids from Rosmarinus officinalis L 
© 2021 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH GmbH www.vjc.wiley-vch.de 233 
Table 2: The 
1
H- and 
13
C-NMR data of compounds 4-5 and reference compounds 
C 
4 5 
*δC
a
 δC
 a,b
 δH
a,c
 (mult., J in Hz) 
&δC
a
 δC
 a,b
 δH
a,c
 (mult., J in Hz) 
1 31.4 31.3 1.22 (m)/3.21 (m) 27.4 27.2 
1.97 (ddd, 1.5, 5.5, 11.5)/3.18 (brd, 
14.0) 
2 18.9 18.9 1.43 (m)/1.67 (m) 19.0 19.0 1.53 (m)/1.64 (m) 
3 41.4 41.1 1.26 (m)/1.50 (m) 38.0 38.0 1.20 (m)/1.43 (m) 
4 33.6 33.6 - 31.4 31.4 - 
5 52.7 52.7 1.41 (m) 50.9 50.9 2.28 (s) 
6 19.0 19.0 1.63 (m)/1.70 (m) 75.3 75.4 4.35 (d, 3.0) 
7 32.0 32.0 2.85 (m) 75.7 75.8 4.66 (d, 3.0) 
8 130.0 130.1 - 126.6 126.7 - 
9 127.5 127.5 - 124.6 124.4 - 
10 44.0 44.0 - 47.0 47.1 - 
11 142.1 142.1 - 142.7 142.4 - 
12 142.2 142.1 - 141.4 141.9 - 
13 132.5 132.4 - 134.6 135.0 - 
14 118.9 118.9 6.52 (s) 120.8 120.6 6.77 (s) 
15 27.2 27.2 3.20 (m) 27.2 27.3 3.10 (m) 
16 22.5 22.6 1.22 (d, 6.5) 22.2 22.2 1.20 (d, 7.0) 
17 22.2 22.3 1.23 (d, 6.5) 22.3 22.4 1.21 (d, 7.0) 
18 33.8 33.9 0.88 (s) 22.0 22.0 0.92 (s) 
19 22.8 22.8 0.97 (s) 31.3 31.4 1.01 (s) 
20 67.3 67.2 
3.93 (d, 9.5) / 4.47 
(d, 9.5) 
179.1 179.3 - 
-CH2CH3 66.2 66.2 3.85 (m) 
-CH2CH3 15.8 15.8 1.32 (t, 6.5) 
Measured in a)CDCl3, 
b)125 MHz, c)500 MHz. *)δC of 11,12,20-trihydroxy-abieta-8,11,13-triene
[19], &)δC of 7α-ethoxyrosmanol.
[20]
Table 3: Inhibitory effects of compounds 1-5 in the LPS induced NO production in RAW 264.7 cells 
Compounds Concentration (µM) Inhibition (%) Cell viability (%) 
1 20 43.6±1.9 97.8±1.1 
100 34.5±0.9 
2 20 51.6±1.5 103.8±1.8 
100 17.9±1.4 
3 20 26.7±1.9 99.8±2.4 
100 6.6±3.1 
4 20 26.7±1.4 102.8±2.7 
100 78.5±2.2 
5 20 20.5±2.4 96.8±3.0 
100 10.1±2.1 
L-NMMA
a
 20 82.2±2.5 95.2±2.1 
a)
Positive control. 
Acknowledgement. This research is funded by the 
Vietnam National University, Hanoi (VNU) under 
project number QG.19.11. 
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Corresponding author: Le Thi Huyen 
VNU University of Science, Vietnam National University, Hanoi 
19, Le Thanh Tong, Hoan Kiem, Hanoi 10000, Viet Nam
E-mail: lethihuyen@hus.edu.vn.