Sonochemical enzyme-catalyzed regioselective acylation of flavonoid glycosides

Article abstract of DOI:10.1016/j.bioorg.2016.01.005

This work compares a highly efficient and alternative method of sonication-assisted lipase catalyzed acylation of quercetin-3-O-glucoside and phloretin-2′-glucoside, using Candida antarctica lipase B (Novozyme 435), with a range of fatty acids.

Full text of DOI:10.1016/j.bioorg.2016.01.005

Bioorganic Chemistry 65 (2016) 17–25
Contents lists available at ScienceDirect
Bioorganic Chemistry
journal homepage: www.elsevier.com/locate/bioorg
Short communication
Sonochemical enzyme-catalyzed regioselective acylation of flavonoid
glycosides
⇑
Ziaullah, H.P. Vasantha Rupasinghe
Department of Environmental Sciences, Faculty of Agriculture, Dalhousie University, Truro, Nova Scotia B2N 5E3, Canada
a r t i c l e i n f o
a b s t r a c t
Article history:
This work compares a highly efficient and alternative method of sonication-assisted lipase catalyzed
acylation of quercetin-3-O-glucoside and phloretin-20-glucoside, using Candida antarctica lipase
B
Received 29 November 2015
Revised 12 January 2016
Accepted 23 January 2016
Available online 23 January 2016
(Novozyme 435Ò), with a range of fatty acids. In this study, sonication-assisted irradiation coupled with
stirring has been found to be more efficient and economical than conventional reaction conditions.
Sonication-assisted acylation accelerated the reactions and reduced the time required by 4–5 folds.
Ó 2016 Elsevier Inc. All rights reserved.
Keywords:
Flavonoids
Isoquercitrin
Phloridzin
Acylation
Sonication-assisted irradiation
Candida antarctica lipase B
NMR spectroscopy
1. Introduction
In principle, ultrasound is a mechanical rather than an electro-
magnetic wave. It is an oscillating sound wave with a frequency
Lipases, produced from microorganisms, play a pivotal role in
industrial applications. They comprise an important group of
enzymes that are used in biotechnology and have numerous indus-
trial applications in dairy, food and pharmaceutical industries [1,2].
They are able to catalyze hydrolysis, alcoholysis, aminolysis,
acidolysis, esterification and transesterification in different media
[3–5]. The major advantages of using lipases over synthetic or semi
synthetic methods are their wide range of substrates with higher
degree of regio-, chemo- and stereo-selectivity under mild reaction
conditions [6].
Lipases have gained considerable attention from food chemistry
as well as biotechnology sectors for the synthesis of esters of nat-
ural flavors and food colors [7]. Recently, the term ‘‘natural” flavors
have been defined as substances that can be extracted from natural
sources such as plants, fruits or vegetables or prepared by
enzymatic or microbial processes. Interestingly, it has been found
that consumers are more convinced with the products if they
are labeled as ‘‘natural” as compared to those labeled as
‘‘synthetic” [8]. Therefore, lipase catalyzed esterification has been
investigated by many scientists to synthesize esters for industrial
applications [9–13].
greater than the upper limit of the human hearing range
(20 kHz). The ultrasound devices operate with frequencies from
20 kHz up to several GHz. Ultrasonication is considered as a
‘‘green” technology as well as it efficiently reduces the process
time as compared to conventional mixing. Moreover, it is econom-
ical due to relatively low consumption of energy [14].
Ultrasonics has become an effective tool in green chemistry,
synthetic organic chemistry, biological reactions and biotechnol-
ogy during last few decades due to its capability of increasing
the reaction rates and yields [15–17]. The reactions that require
several days under conventional conditions can now be completed
in few hours by this efficient and environmentally green technol-
ogy. In general, ultrasound technology has the capability of
increasing the interaction between phases by cavitations which
results from the collapse of bubbles. The ultrasonic jet then dis-
rupts the boundaries of the phases and causes exponential increase
in emulsification [14,18]. In addition, the application of ultrasound
to a suspension results in an increase in mixing and mass transfer
[15,19]. Kwiatkowska et al. [17] has reported that the ultrasound
frequency increases the geometric and electronic complementari-
ness between substrate and enzyme interaction of the enzyme-
substrate model. Nevertheless, it is notable that the influence of
ultrasonics on the stability and activity of enzymes depends on
the sonication parameters especially the power (frequency) of
⇑
Corresponding author.
E-mail address: vrupasinghe@dal.ca (H.P.V. Rupasinghe).
http://dx.doi.org/10.1016/j.bioorg.2016.01.005
0045-2068/Ó 2016 Elsevier Inc. All rights reserved.

18
Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
ultrasound. Some scientists have suggested that the ultrasound
influence the reaction kinetics which is apparent from the reduc-
tion of esterification reaction time [20,21]. However, its application
to enzyme catalysis is still hardly known and to the best of our
knowledge the application of ultrasound-assisted technology for
lipase-catalyzed synthesis of flavor esters is the latest of its kind
[9–13,15–17,20–36].
The enzyme-catalyzed esterification and transesterification of
flavonoid glycosides with various acyl donors under conventional
conditions has been well documented in previous reports
[22–36]. However, our present investigation provides an efficient,
alternative and greener approach for lipase-catalyzed acylation
of quercetin-3-O-glucoside (isoquercitrin) and phloretin-20-
glucoside (phloridzin) with fatty acids of different chain lengths
by using ultrasonic technology. Our present study has been
supported by different analytical techniques including NMR
spectroscopy.
rate when reaction temperature is between 40 and 45 °C. When
the temperature was further elevated to 60 °C, the activity of
enzyme accelerated but on TLC it was noticed that further acyla-
tion occurs at some different site of the flavonoid glycosides. How-
ever, these trace amounts were not isolated due to their lower
quantity. At elevated temperature, possibly the cavitation events
increased which probably helped in increasing the mass transfer
and thus consequently decreases the selectivity of enzyme. At
above 60 °C we noticed that the activity of the enzyme decreases
drastically. This decrease in the enzyme activity at elevated tem-
perature could be due to thermal denaturation of enzyme. There-
fore, considering the selectivity of the enzyme, conversion and
feasibility, the optimum temperature found for the ultrasonic
assisted synthesis was 40–45 °C.
2.3. Effect of power of ultrasound
The different power grades of ultrasound are important factors
for reactions under ultrasound irradiation. Herein, we selected two
different powers of 20 kHz ultrasound, namely 100 and 120 W for
our ultrasound-assisted reactions with intervals of 15–20 min
each. The reactions accelerated with increase in the ultrasonic
intensities which possibly affected the activity of enzyme. In case
of lipase Amano PS-catalyzed acylations, Brenelli and Fernandes
[38] have proved that rates of acyl transfer increased several folds
by using ultrasonic technology as compared to conventional mag-
netic stirring [39,15,40]. In our case, at the experimental acoustic
power, the immobilized lipase (Novozyme 435Ò) accelerated the
reaction by 4–5 folds but did not show any deactivation at the opti-
mum temperature.
2. Results and discussion
2.1. Chemistry
Esterification of phloridzin and isoquercitrin with 20 different
fatty acids of various chain lengths (C4–C18) were carried out at
40–45 °C in extra dry acetone along with ultrasonication or sonica-
tion coupled with stirring. The biocatalytic reactions were started
by the addition of Candida antarctica lipase B (Novozyme 435Ò;
purchased from Sigma–Aldrich (Mississauga, ON, Canada) into a
solution of flavonoid glycosides and fatty acids in acetone, in the
presence of flame dried molecular sieves (3 Å) (Scheme 1, Table 1).
In the conventional method, the reactions were carried out accord-
ing to our previously described procedure in Ziaullah et al. [37].
2.4. Ultrasonic irradiation vs conventional stirring method
2.2. Effect of temperature
These esterifications were conducted at optimized conditions to
compare the conversion obtained for enzyme catalyzed transester-
ification with ultrasonic irradiation and ultrasonication coupled
with conventional stirring. The results obtained are shown in
Table 1. It was found that when the flavonoid glycoside esters
are synthesized by ultrasonic irradiation coupled with stirring,
the reactions complete in 2.5–4 h whereas with conventional
To study the effect of reaction temperature on the esterification,
reactions were carried out under ultrasonic irradiation or ultra-
sonic irradiation coupled with stirring at different temperatures
ranging from 40 to 70 °C. During optimization of this method we
discovered that the activity of enzyme is at the optimum reaction
Scheme 1. (i) Immobilized lipase B, from Candida antarctica (Novozyme 435Ò), 3 Å molecular sieves, ultrasonication, Acetone, 40–45 °C, 2–3.5 h or ultrasonication coupled
with stirring (3–5 h); R = butyric, octanoic, dodecanoic, palmitic, oleic, stearic, linoleic, linolenic, eicosapentaenoic, docosahexaenoic acids or their corresponding esters.

Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
19
Table 1
Reaction time and yield for ultrasonication-based acylation of fatty acids with flavonoids.
Flavonoids
Fatty acid
Structure of the product
Reaction time (h)
Yielda
(%)
Conventional
[37]
Ultrasonication Ultrasonication
and Stirring
Phloridzin
Butyric acid (C4H8O2)
24
3.5
2
81b
Phloridzin
Octanoic acid (C8H16O2)
24
3.5
2
84b
Phloridzin
Dodecanoic acid
(C12H24O2)
24
4
3
97
Phloridzin
Palmitic acid (C16H32O2)
24
4.5
3
97
Phloridzin
Stearic acid (C18H36O2)
24
4.5
3
96
(continued on next page)

20
Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
Table 1 (continued)
Flavonoids
Fatty acid
Structure of the product
Reaction time (h)
Yielda
(%)
Conventional
[37]
Ultrasonication Ultrasonication
and Stirring
Phloridzin
Oleic acid (C18H34O2)
24
4
2.5
93
Phloridzin
Linoleic acid (C18H32O2)
24
4
3
89
Isoquercitrin Butyric acid (C4H8O2)
24
3
2
83b
Isoquercitrin Octanoic acid (C8H16O2)
24
3
2.5
81b
Isoquercitrin Dodecanoic acid
(C12H24O2)
24
3.5
3
92
Isoquercitrin Palmitic acid (C16H32O2)
24
4.5
3
93

Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
21
Table 1 (continued)
Flavonoids
Fatty acid
Structure of the product
Reaction time (h)
Yielda
(%)
Conventional
[37]
Ultrasonication Ultrasonication
and Stirring
Isoquercitrin Stearic acid (C18H36O2)
24
4.5
3
96
Isoquercitrin Oleic acid (C18H34O2)
24
4
3
93
Isoquercitrin Linoleic acid (C18H32O2)
24
4.2
3
91
a
There is no significant difference in yields of all the three methods.
Compounds were volatile and some quantity lost during evaporation on rotavap.
b
stirring reactions completed in 24 h [40]. Thus, it can be postulated
that ultrasonics induces an emulsion and mass transfer, which
accelerates the reactions as compared to conventional stirring
method. However, very little is known so far about the actual effect
of ultrasound on enzyme behavior which requires a much deeper
investigation to obtain more detailed and precise information.
purified by column chromatography, using silica gel 60 (0.040–
0.063 mm; 230–400 mesh, Merck, Darmstadt, Germany) and eluted
with acetone toluene. The samples were analyzed by 1H NMR and
13C NMR spectroscopic techniques in solvent DMSO-d6 or MeOD,
on Bruker ADVANCE 300 MHz spectrometer. The IR data was col-
lected on Nicolet 6700 FT-IR spectrometer.
2.7. Conclusion
2.5. Reusability of enzyme
The present work reports fourteen esters of two series of flavo-
noid glycosides with a range of fatty acids of various chain lengths
under ultrasound irradiation as well as ultrasound irradiation cou-
pled with stirring while using Novozyme 435Ò in organic solvent.
Our results proved the significance of ultrasonics for the selective
esterification of flavonoid glycosides under greener and milder
conditions. It has been found that if sonication is coupled with stir-
ring it provides the most efficient enzyme catalyzed esterification
method.
Recycling of the enzyme is crucial factor to test the commercial
viability of the enzyme catalyzed process. To assess the reusability
of the enzyme, the immobilized enzyme was filtered from the reac-
tion medium after completion of esterification (Table 2). The
recovered biocatalyst was washed with acetone and dried for
18–20 h under phosphorous pentoxide (P2O5) in a desiccator and
reused in a new fresh reaction to study the reusability extent.
We reused the enzyme for 3-cycles but found that the conversion
decreases gradually after each cycle. Nevertheless, it was noticed
that the enzyme activity loss is due to physical breakage of enzyme
supporting material during the sonication process.
3. Experimental
2.6. Analytical methods
3.1. General procedure for the biocatalytic esterification reaction of
phloridzin and isoquercitrin (2–11 and 13–21)
The progress of esterification was monitored by thin-layer chro-
matography (TLC) on silica gel 60 F254 plates from Merck (Darm-
To flame dried 3 Å molecular sieves in an amber color vial, was
added phloridzin (0.100 g; 0.23 mmol), butyric acid (0.06 ml,
0.69 mmol), Novozyme 435Ò (0.300 g). It was followed by the
addition of dry acetone (5 ml). The reaction was carried out in an
stadt, Germany), using
a solvent system of acetone/toluene
(40:60, few drops of acetic acid). The products were detected by
using anisaldehyde as spray reagent. The acylated products were

22
Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
Table 2
Reusability of enzyme and percentage yields.
Compound Quantity of enzyme utilized
(1st cycle) (g)a
Yield (1st
cycle) (%)
Quantity of recovered enzyme
(2nd cycle) (g)b
Yield (2nd
cycle) (%)
Quantity of recovered enzyme
(3rd cycle) (g)c
Yield (3rd
cycle) (%)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0.300
0.302
0.303
0.302
0.304
0.302
0.301
0.302
0.303
0.304
0.303
0.303
0.302
0.303
81
84
97
97
96
93
89
83
81
92
93
96
93
91
0.293
0.295
0.297
0.296
0.297
0.296
0.294
0.292
0.294
0.295
0.293
0.296
0.295
0.294
76
77
89
90
91
87
83
76
75
84
86
88
84
83
0.284
0.286
0.290
0.289
0.287
0.288
0.284
0.283
0.283
0.284
0.283
0.288
0.284
0.283
68
69
80
83
82
82
77
68
67
77
80
79
75
74
a
b
c
1st cycle: enzyme utilized in the reaction mixture was fresh and dried.
2nd cycle: enzyme recovered and reutilized in the second cycle.
3rd cycle: enzyme recovered and re-reutilized in the third cycle.
ultrasonic bath of 20 kHz/1000 W (model 750D, VWR, West
Chester, PA, USA) and exposed for 3.5–5 h under ultrasound irradi-
ation alone (for 15–20 min each with 10 min interval in between)
and for 2–3.5 h (for 15–20 min each with 10 min interval in
between) under ultrasound irradiation coupled with stirring at
40–45 °C (Table 1).
The progress of reaction was monitored by thin layer chro-
matography, followed by staining with anisaldehyde spray reagent
and then heating at 110 °C. After completion of reaction, it was
filtered, evaporated and chromatographed (acetone:toluene;
35:75–50:50) to get the pure butyric acid ester (2) of phloridzin.
All other reactions followed the same procedure and produced
esters 2–8 and 9–15, with yields in the range of 81–97%. The pure
compounds were then analyzed by IR and NMR spectroscopy.
J = 10.8 Hz, H-6a00), 4.12 (dd, 1H, J = 10.8 Hz, 6.8 Hz, H-6b00), 3.62
(br t, 1H, J = 7.7 Hz, H-400), 3.49–3.17 (m, 6H, 2 ꢁ H , H-200, H-300,
a
H-500, OH), 2.78 (br t, 2H, J = 7.3 Hz, 2 ꢁ Hb), 2.27 (br t, 2H,
J = 7.4 Hz, 2 ꢁ H-200), 1.52–1.42 (m, 2H, 2 ꢁ H-300), 1.24–1.16 (m,
8H, 4 ꢁ CH2), 0.81 (br t, 3H, J = 6.3 Hz, CH3); 13C NMR (DMSO-d6,
75 MHz): d 205.12 (CO), 173.30 (OCO), 165.83 (C-40), 164.92 (C-
60), 161.06 (C-20), 155.75 (C-4), 131.94 (C-1), 129.60 (C-2, C-6),
115.41 (C-3, C-5), 105.60 (C-10), 101.00 (C-100), 97.36 (C-30), 94.94
(C-50), 76.85 (C-300), 74.34 (C-500), 73.55 (C-200), 70.24 (C-400), 63.49
(C-600), 45.47 (C ), 33.86 (C-2000), 31.58 (Cb), 29.52, 28.85, (C-4000,
a
C-5000, C-6000), 24.85 (C-3000), 22.50 (C-7000), 14.38 (C-8000).
3.1.3. (6-{3,5-Dihydroxy-2-[3-(4-hydroxyphenyl)propanoyl]phenoxy}-
3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)methyl dodecanoate (4)
Yield: 97%; light yellow solid; Rf: 0.53 (acetone:toluene; 5:5:
few drops of AcOH); IR (KBr) cmꢀ1: 3382, 2943, 2837, 2525,
2246, 2048, 1714, 1635, 1596, 1517, 1458, 1264, 1119, 1027,
736, 658; 1H NMR (DMSO-d6, 300 MHz): d 13.49 (s, 1H, ArOH),
10.52 (br s, 1H, ArOH), 7.03 (d, 2H, J = 8.4 Hz, H-2, H-6), 6.65 (d,
2H, J = 8.4 Hz, H-3, H-5), 6.10 (d, 1H, J = 2.1 Hz, H-30), 5.95 (d, 1H,
J = 2.1 Hz, 1H, H-50), 5.36 (br.s, 1H, OH), 5.29 (br s, 1H, OH), 5.26
(br s, 1H, OH), 4.98 (d, 1H, J = 7.2 Hz, H-100), 4.32 (br d, 1H,
J = 10.2 Hz, H-6a00), 4.12 (dd, 1H, J = 10.2 Hz, 6.8 Hz, H-6b00), 3.61
3.1.1. (6-{3,5-Dihydroxy-2-[3-(4-hydroxyphenyl)propanoyl]phenoxy}-
3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)methyl butyrate (2)
Yield: 81%; light yellow liquid; Rf: 0.53 (acetone:toluene; 5:5:
few drops of AcOH); IR (KBr) cmꢀ1: 3386, 2955, 2836, 2529,
2241, 2043, 1715, 1632, 1589, 1511, 1453, 1265, 1118, 1029,
916, 736, 653; 1H NMR (MeOD, 300 MHz): d 13.47 (s, 1H, ArOH),
10.56 (br s, 1H, ArOH), d 7.06 (d, 2H, J = 8.5 Hz, H-2, H-6), 6.71 (d,
2H, J = 8.5 Hz, H-3, H-5), 6.15 (d, 1H, J = 2.1 Hz, H-30), 6.00 (d, 1H,
J = 2.1 Hz, 1H, H-50), 5.02 (br d, 1H, J = 7.5 Hz, H-100), 4.40 (dd, 1H,
J = 11.8 Hz, J = 2.1 Hz, H-6a00), 4.27 (dd, 1H, J = 11.8 Hz, 6.2 Hz,
H-6b00), 3.70–3.63 (br m, 1H, J = 7.7 Hz, H-400), 3.51–3.31 (m, 6H,
(br t, 1H, J = 7.65 Hz, H-400), 3.48–3.19 (m, 6H, 2 ꢁ H , H-200, H-300,
a
H-500, OH), 2.78 (br t, 2H, J = 7.3 Hz, 2 ꢁ Hb), 2.26 (br t, 2H,
J = 7.3 Hz, 2 ꢁ H-200), 1.52–1.41 (m, 2H, 2 ꢁ H-300), 1.25–1.13 (m,
16H, 8 ꢁ CH2), 0.84 (br t, 3H, J = 6.4 Hz, CH3); 13C NMR (DMSO-
d6, 75 MHz): d 205.10 (CO), 173.29 (OCO), 165.89 (C-40), 164.94
(C-60), 161.09 (C-20), 155.75 (C-4), 131.93 (C-1), 129.59 (C-2, C-6),
115.41 (C-3, C-5), 105.57 (C-10), 101.04 (C-100), 97.38 (C-30), 94.95
(C-50), 76.86 (C-300), 74.34 (C-500), 73.55 (C-200), 70.25 (C-400), 63.52
2 ꢁ H , H-200, H-300, H-500, OH), 2.88 (br t, 2H, J = 7.6 Hz, 2 ꢁ Hb),
a
2.29 (br t, 2H, J = 7.4 Hz, 2 ꢁ H-2000), 1.56 (m, 2H, 2 ꢁ H-3000), 0.88
(br t, 3H, J = 7.4 Hz, CH3); 13C NMR (MeOD, 75 MHz): d 205.19
(CO), 173.92 (OCO), 166.14 (C-40), 164.48 (C-60), 160.77 (C-20),
154.98 (C-4), 132.46 (C-1), 129.02 (C-2, C-6), 114.73 (C-3, C-5),
105.59 (C-10), 100.60 (C-100), 97.07 (C-30), 94.48 (C-50), 76.89
(C-300), 74.24 (C-500), 73.28 (C-200), 70.11 (C-400), 62.95 (C-600), 45.57
(C-600), 45.47 (C ), 33.86 (C-2000), 31.79 (Cb), 29.50, 29.39, 29.38,
a
29.21, 29,14, 28.90 (C-4000, C-5000, C-6000, C-7000, C-8000, C-9000, C-10000),
24.85 (C-3000), 22.59 (C-11000), 14.42 (C-12000).
(C ), 35.46 (C-2000), 29.53 (Cb), 18.03 (C-3000), 12.56 (C-4000).
a
3.1.2. (6-{3,5-Dihydroxy-2-[3-(4-hydroxyphenyl)propanoyl]phenoxy}-
3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)methyl octanoate (3)
Yield: 84%; light yellow liquid; Rf: 0.53 (acetone:toluene; 5:5:
few drops of AcOH); IR (KBr) cmꢀ1: 3387, 2951, 2835, 2519,
2241, 2044, 1715, 1637, 1593, 1516, 1451, 1266, 1112, 1025,
913, 739, 647; 1H NMR (DMSO-d6, 300 MHz): d 13.47 (s, 1H, ArOH),
10.56 (br s, 1H, ArOH), 7.03 (d, 2H, J = 8.3 Hz, H-2, H-6), 6.64 (d, 2H,
J = 8.3 Hz, H-3, H-5), 6.10 (d, 1H, J = 1.6 Hz, H-30), 5.95 (d, 1H,
J = 1.6 Hz, 1H, H-50), 5.36 (br.s, 1H, OH), 5.29 (br s, 1H, OH), 5.25
(br s, 1H, OH), 4.99 (d, 1H, J = 6.9 Hz, H-100), 4.32 (br d, 1H,
3.1.4. (6-{3,5-Dihydroxy-2-[3-(4-hydroxyphenyl)propanoyl]phenoxy}-
3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)methyl palmitate (5)
Yield: 97%; light yellow solid; Rf: 0.53 (acetone:toluene; 5:5:
few drops of AcOH); IR (KBr) cmꢀ1: 3388, 2944, 2836, 2527,
2244, 2048, 1716, 1634, 1593, 1513, 1454, 1266, 1117, 1024,
918, 738, 659; 1H NMR (DMSO-d6, 300 MHz): d 13.49 (s, 1H, ArOH),
10.53 (br s, 1H, ArOH), 7.04 (d, 2H, J = 8.3 Hz, H-2, H-6), 6.65 (d, 2H,
J = 8.3 Hz, H-3, H-5), 6.11 (br s, 1H, H-30), 5.95 (br s, 1H, H-50), 5.38
(br.s, 1H, OH), 5.37 (br s, 1H, OH), 5.26 (br s, 1H, OH), 4.99 (d, 1H,
J = 6.81 Hz, H-100), 4.34 (br d, 1H, J = 11.5 Hz, H-6a00), 4.12 (dd, 1H,

Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
23
J = 11.5 Hz, 6.7 Hz, H-6b00), 3.65 (br t, 1H, J = 8.3 Hz, H-400), 3.64–
2928, 2856, 2253, 1711, 1628, 1599, 1515, 1454, 1378, 1263,
1204, 1173, 1080, 907, 733, 650; 1H NMR (DMSO-d6, 300 MHz):
d 10.67 (br s, 1H, OH), 9.23 (br s, 1H, OH), 7.08 (d, 2H, J = 8.1 Hz,
H-2, H-6), 6.70 (d, 2H, J = 8.1 Hz, H-3, H-5), 6.16 (d, 1H, J = 1.2 Hz,
H-30), 6.01(d, 1H, J = 1.2 Hz, H-50), 5.47 (br s, 1H, OH), 5.40–5.27
(m, 5H, H-9000, H-10000, H-12000, H-13000, OH), 5.04 (d, 1H, J = 6.9 Hz,
H-100), 4.37 (br d, 1H, J = 11.4 Hz, H-6a00), 4.18 (dd, 1H, J = 11.4 Hz,
6.6 Hz, H-6b00), 3.66 (br t, 1H, J = 7.8 Hz, H-400), 3.57 (br s, 2 ꢁ OH),
3.18 (m, 6H, 2 ꢁ H , H-200, H-300, H-500, OH), 2.79 (br t, 2H,
a
J = 7.2 Hz, 2 ꢁ Hb), 2.27 (br t, 2H, J = 7.3 Hz, 2 ꢁ H-200), 1.47 (m,
2H, 2 ꢁ H-300), 1.27–1.16 (m, 24H, 12(CH2)), 0.85 (br t, 3H,
J = 6.8 Hz, CH3); 13C NMR (DMSO-d6, 75 MHz): d 205.09 (CO),
173.29 (OCO), 165.87 (C-40), 164.92 (C-60), 161.09 (C-20), 155.75
(C-4), 131.92 (C-1), 129.58 (C-2, C-6), 115.40 (C-3, C-5), 105.57
(C-10), 101.03 (C-100), 97.36 (C-30), 94.94 (C-50), 76.85 (C-300), 74.33
(C-500), 73.55 (C-200), 70.25 (C-400), 63.52 (C-600), 45.46 (C ), 33.86
3.48–3.22 (m, 5H, 2 ꢁ H , H-200, H-300, H-500), 2.83 (br t, 2H,
a
a
(C-2000), 31.79 (Cb), 29.54, 29.48, 29.38, 29.21, 29,14, 28.90 (C-4000,
C-5000, C-6000, C-7000, C-8000, C-9000, C-10000, C-11000, C-12000, C-13000,
C-14000), 24.85 (C-3000), 22.59 (C-15000), 14.42 (C-16000).
J = 6.9 Hz, 2 ꢁ Hb), 2.74 (br t, 2H, J = 5.4 Hz, 2 ꢁ H-11000), 2.30 (br t,
2H, J = 7.5 Hz, 2 ꢁ H-2000), 2.15–1.99 (m, 4H, 2 ꢁ H-8000, 2 ꢁ H-14000),
1.53–1.48 (m, 2H, 2 ꢁ H-3000), 1.37–1.18 (m, 14H, 7(CH2)), 0.86 (br
t, 3H, J = 6.6 Hz, CH3); 13C NMR (DMSO-d6, 75 MHz): d 205.42
(CO), 173.45 (OCO), 166.20 (C-40), 165.16 (C-60), 161.38 (C-20),
156.09 (C-4), 132.36 (C-1), 130.50 (C-9000, C-13000), 129.75 (C-2,
C-6), 128.48 (C-10000, C-12000), 115.84 (C-3, C-5), 106.33 (C-10),
101.68 (C-100), 97.94 (C-30), 95.56 (C-50), 77.43 (C-300), 74.89 (C-
3.1.5. (6-{3,5-Dihydroxy-2-[3-(4-hydroxyphenyl)propanoyl]phenoxy}-
3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)methyl stearate (6)
Yield: 96%; light yellow solid; Rf: 0.53 (acetone:toluene; 4:6:
few drops of AcOH); IR (KBr) cmꢀ1: 3383, 2944, 2832, 2523,
2247, 2043, 1719, 1631, 1591, 1512, 1450, 1269, 1113, 1028,
913, 737, 652; 1H NMR (DMSO-d6, 300 MHz): d 13.55 (s, 1H, ArOH),
9.18 (br s, 1H, ArOH), 7.06 (d, 2H, J = 8.4 Hz, H-2, H-6), 6.67 (d, 2H,
J = 8.4 Hz, H-3, H-5), 6.13 (d, 1H, 1.8 Hz, H-30), 5.98 (d, 1H,
J = 1.8 Hz, H-50), 5.46 (br.s, 1H, OH), 5.37 (br s, 2H, 2OH), 5.04 (d,
1H, H-100), 4.35 (br d, 1H, J = 11.6 Hz, H-6a00), 4.14 (dd, 1H,
J = 11.6 Hz, 6.9 Hz, H-6b00), 3.65 (br t, J = 7.2 Hz, H-400), 3.46–3.20
500), 74.03 (C-200), 70.80 (C-400), 63.88 (C-600), 45.66 (C ), 34.23 (C-
a
2000), 31.64 (Cb), 29.95 (C-7000), 29.73 (C-15000), 29.44 (C-4000), 29.23
(C-5000, C-6000, C-11000), 27.39 (C-8000, C-14000), 25.99 (C-16000), 25.13
(C-3000), 22.65 (C-17000), 14.47 (C-18000).
3.1.8. (6-{[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-4Hchromen-
3-yl]oxy}-4,5-dihydroxytet-rahydro-2H-pyran-2-yl)methyl butyrate (9)
Yield: 83%; yellowish solid; Rf: 0.42 (acetone:toluene; 1:1: few
drops of AcOH); IR (KBr) cmꢀ1: 3453, 3276, 3072, 3003, 2927,
2859, 2543, 2247, 2131, 1989, 1834, 1763, 1659, 1450, 1363,
1307, 1203, 1169, 1053, 823, 737, 627; 1H NMR (DMSO-d6,
300 MHz): d 12.65 (br.s, 1H, ArOH), 7.54–7.50 (m, 2H, H-20, H-60),
6.84 (br d, 1H, J = 9.0 Hz, H-50), 6.40 (d, 1H, J = 1.95 Hz, H-8), 6.22
(d, 1H, J = 1.95 Hz, H-6), 5.45 (d, 1H, J = 7.35 Hz, H-100), 5.29–4.99
(m, 3H, 3OH), 4.15 (br.d, 1H, J = 10.0 Hz, H-6a00), 3.97–3.91 (dd,
1H, J = 10.0 Hz, J = 6.87 Hz, H-6b00), 3.55–3.09 (m, 6H, H-200, H-300,
H-400, H-500, 2OH), 1.95 (dd, 2H, J = 7.53 Hz, J = 3.48 Hz, 2 ꢁ H-2000),
1.27–1.17 (m, 3H, 2 ꢁ H-3000, OH), 0.64 (br. t, 3H, J = 7.33 Hz, CH3);
13C NMR (DMSO-d6, 75 MHz): d 177.80 (CO), 172.75 (OCO),
164.72 (C-7), 161.71 (C-5), 156.84, 156.78 (C-2, C-9),
148.98 (C-40), 145.31 (C-30), 133.39 (C-3), 121.94 (C-10), 121.49
(C-60), 116.53 (C-50), 115.58 (C-20), 104.27 (C-10), 101.01
(C-100), 99.14 (C-6), 93.95 (C-8), 76.71 (C-300), 74.57 (C-500), 74.36
(C-200), 70.51 (C-400), 63.34 (C-600), 35.66 (C-2000), 18.25 (C-3000),
13.62 (C-4000).
(m, 6H, 2 ꢁ H , H-200, H-300, H-500, OH), 2.81 (br t, 2H, J = 7.5 Hz,
a
2 ꢁ Hb), 2.30 (t, 2H, J = 7.2 Hz, 2 ꢁ H-200), 1.49 (m, 2H, 2 ꢁ H-300),
1.25–1.19 (m, 28H, 2(CH2)), 0.87 (br t, 3H, J = 6.9 Hz, CH3); 13C
NMR (DMSO-d6, 75 MHz): d 205.34 (CO), 173.44 (OCO), 166.05
(C-40), 165.13 (C-60), 161.30 (C-20), 156.03 (C-4), 132.25 (C-1),
129.72 (C-2, C-6), 115.74 (C-3, C-5), 106.18 (C-10), 101.55 (C-100),
97.79 (C-30), 95.44 (C-50), 77.30 (C-300), 74.77 (C-500), 73.94 (C-200),
70.68 (C-400), 63.81 (C-600), 45.61 (C ), 34.17 (C-2000), 31.96 (Cb),
a
29.84, 29.34, 29.13 (C-4000, C-5000, C-6000, C-7000, C-8000, C-9000, C-10000,
C-11000, C-12000, C-13000, C-14000, C-15000, C-16000), 25.08 (C-3000), 22.73
(C-17000), 14.53 (C-18000).
3.1.6. (6-{3,5-Dihydroxy-2-[3-(4-hydroxyphenyl)propanoyl]phenoxy}-
3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)methyl (Z)-9-
octadecenoate (7)
Yield: 93%; light brownish yellow spongy solid; Rf: 0.56 (Ace-
tone:toluene; 4:6: few drops of AcOH); IR (KBr) cmꢀ1: 3383,
2927, 2855, 2253, 1714, 1627, 1599, 1514, 1455, 1264, 1203,
1078, 908, 734, 650; 1H NMR (DMSO-d6, 300 MHz): d 13.61 (s,
1H, OH), 10.66 (br s, 1H, OH), 9.25 (br s, 1H, OH), 7.09 (d, 2H,
J = 8.7 Hz, H-2, H-6), 6.72 (d, 2H, J = 8.7 Hz, H-3, H-5), 6.17 (d, 1H,
1.8 Hz, H-30), 6.01 (s, 1H, H-50), 5.48–5.29 (m, 4H, H-9000, H-10000),
5.04 (d, 1H, J = 6.9 Hz, H-100), 4.38 (br d, 1H, J = 11.4 Hz, H-6a00),
4.18 (dd, 1H, J = 11.4 Hz, 6.6 Hz, H-6b00), 3.67 (br t, 1H, J = 7.8 Hz,
3.1.9. (6-{[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-4Hchromen-
3-yl]oxy}-4,5-dihydroxytet-rahydro-2H-pyran-2-yl)methyl octanoate
(10)
H-400), 3.55–3.23 (m, 6H, 2 ꢁ H , H-200, H-300, H-500, OH), 2.84 (br t,
Yield: 81%; yellowish solid; Rf: 0.42 (acetone:toluene; 1:1: few
drops of AcOH); IR (KBr) cmꢀ1: 3458, 3277, 3078, 3009, 2925,
2856, 2549, 2246, 2135, 1987, 1833, 1768, 1653, 1459, 1368,
1309, 1206, 1165, 1058, 828, 736, 627; 1H NMR (DMSO-d6,
300 MHz): d 12.65 (br.s, 1H, ArOH), 7.54–7.50 (m, 2H, H-20, H-60),
6.83 (br d, 1H, J = 9.0 Hz, H-50), 6.39 (d, 1H, J = 1.94 Hz, H-8), 6.19
(d, 1H, J = 1.94 Hz, H-6), 5.45 (br. dd, 1H, J = 7.35 Hz, H-100), 5.20
(br. s, 2H, 2OH), 4.17 (br.d, 1H, J = 10.0 Hz, H-6a00), 3.99–3.92 (dd,
1H, J = 10.0 Hz, J = 7.05 Hz, H-6b00), 3.35–3.08 (m, 6H, H-200, H-300,
H-400, H-500, 2OH), 1.99–1.90 (m, 2H, 2 ꢁ H-2000), 1.27–1.01 (m,
12H, 5 ꢁ CH2, 2OH), 0.82 (t, 3H, J = 6.84 Hz, CH3); 13C NMR
(DMSO-d6, 75 MHz): d 177.80 (CO), 172.88 (OCO), 164.62 (C-7),
161.70 (C-5), 156.84, 156.77 (C-2, C-9), 148.94 (C-40), 145.26
(C-30), 133.40 (C-3), 123.03 (C-10), 122.95 (C-60), 116.59 (C-50),
114.49 (C-20), 104.30 (C-10), 102.18 (C-100), 99.91 (C-6), 94.96
(C-8), 77.68 (C-300), 75.33 (C-500), 73.39 (C-200), 71.50 (C-400), 63.31
(C-600), 33.65 (C-2000), 31.96 (C-1400), 30.40, 28.74, 26.97 (C-4000,
C-5000, C-6000), 24.67 (C-3000), 22.51 (C-7000), 13.57 (C-8000).
a
2H, J = 6.9 Hz, 2 ꢁ Hb), 2.32 (br t, 2H, J = 6.9 Hz, 2 ꢁ H-200), 2.01–
1.98 (m, 4H, 2 ꢁ H-800, 2 ꢁ H-1100), 1.54–1.50 (m, 2H, 2 ꢁ H-300),
1.27–1.20 (m, 20H, 10(CH2)), 0.87 (br t, 3H, J = 6.9 Hz, CH3); 13C
NMR (DMSO-d6, 75 MHz): d 205.37 (CO), 173.41 (OCO), 166.13
(C-40), 165.15 (C-60), 161.34 (C-20), 156.06 (C-4), 132.30 (C-1),
130.30 (C-900, C-1000), 129.73 (C-2, C-6), 115.78 (C-3, C-5), 106.25
(C-10), 101.63 (C-100), 97.86 (C-30), 95.50 (C-50), 77.37 (C-300), 74.83
(C-500), 73.98 (C-200), 70.74 (C-400), 63.85 (C-600), 45.63 (C ), 34.19
a
(C-200), 31.97 (Cb), 29.83 (C-7000, C-12000), 29.54 (C-15000), 29.33 (C-
4000, C-5000, C-14000), 29.20 (C-6000, C-13000, C-16000), 27.33 (C-8000, C-
11000), 25.10 (C-3000), 22.74 (C-17000), 14.50 (C-18000).
3.1.7. (6-{3,5-Dihydroxy-2-[3-(4-hydroxyphenyl)propanoyl]phenoxy}-
3,4,5-trihydroxytetrahydro-2H-pyran-2-yl)methyl (9Z,12Z)-9,12-octa-
decadienoate (8)
Yield: 89%; light brownish yellow spongy solid; Rf: 0.57 (ace-
tone:toluene; 4:6: few drops of AcOH); IR (KBr) cmꢀ1: 3396,

24
Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
3.1.10. (6-{[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-4H-chro-
men-3-yl]oxy}-4,5-dihy-droxy-tetrahydro-2H-pyran-2-yl)methyl
dodecanoate (11)
C-11000, C-12000, C-13000, C-14000, C-15000), 24.95 (C-3000), 22.74 (C-17000),
14.51 (C-18000).
Yield: 92%; yellowish solid; Rf: 0.42 (acetone:toluene; 1:1: few
drops of AcOH); IR (KBr) cmꢀ1: 3453, 3276, 3072, 3003, 2927,
2859, 2543, 2247, 2131, 1989, 1834, 1763, 1659, 1450, 1363,
1307, 1203, 1169, 1053, 823, 737, 627; 1H NMR (DMSO-d6,
3.1.13. (6-{[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-4Hchro-
men-3-yl]oxy}-3,4,5-trihydroxy-tetrahydro-2H-pyran-2-yl)methyl
(Z)-9-octadecenoate (14)
Yield: 93%; greenish yellow spongy solid; Rf: 0.58 (acetone:-
toluene; 1:1: few drops of AcOH); IR (KBr) cmꢀ1: 3373, 3065,
2947, 2836, 2497, 2251, 2121, 2042, 1898, 1763, 1640, 1596,
1560, 1459, 1448, 1229, 1165, 1026, 942, 739; 1H NMR
(DMSO-d6, 300 MHz): d 11.45–9.01 (br.s, 2H, ArOH), 7.53 (d, 2H,
J = 9.0 Hz, H-20, H-60), 6.85 (d, 1H, J = 9.0 Hz, H-50), 6.41 (d, 1H,
J = 1.8 Hz, H-8), 6.22 (d, 1H, J = 1.8 Hz, H-6), 5.48–5.25 (m, 5H,
H-900, H-1000, H-100, 2OH), 4.20 (br.d, 1H, J = 11.7 Hz, H-6a00), 3.99
(dd, 1H, J = 11.7 Hz, J = 7.2 Hz, H-6b00), 3.45–3.13 (m, 6H, H-200, H-
300, H-400, H-500, 2 ꢁ OH), 2.06–1.97 (m, 6H, 2 ꢁ H-2000, 2 ꢁ H-8000,
2 ꢁ H-11000), 1.27–1.09 (m, 23H, 11 ꢁ CH2), 0.85 (br t, 3H,
J = 6.6 Hz, CH3); 13C NMR (DMSO-d6, 75 MHz): d 178.12 (CO),
173.05 (OCO), 164.99 (C-7), 162.06 (C-5), 157.12 (C-2, C-9),
149.21 (C-40), 145.56 (C-30), 133.92 (C-3), 130.29 (C-900, C-1000),
122.16 (C-10), 121.93 (C-60), 116.95 (C-50), 115.88 (C-20), 104.65
(C-10), 101.65 (C-100), 99.42 (C-6), 94.18 (C-8), 77.23 (C-300), 74.98
(C-500), 74.76 (C-200), 70.98 (C-400), 63.75 (C-600), 33.96 (C-2000),
31.92 (C-16000), 29.79 (2C), 29.49, 29.29 (3C), 29.13, 29.03 (C-4000,
C-5000, C-6000, C-7000, C-12000, C-13000, C-14000, C-15000), 27.31 (C-8000,
C-11000), 27.90 (C-3000), 22.69 (C-17000), 14.49 (C-18000).
300 MHz):
d 12.62 (s, 1H, ArOH), 10.88 (br s, 1H, ArOH),
7.53–7.50 (m, 2H, H-20, H-60), 6.82 (br d, 1H, J = 8.79 Hz, H-50),
6.39 (d, 1H, J = 2.04 Hz, H-8), 6.19 (d, 1H, J = 2.04 Hz, H-6),
5.46–5.41 (m, 2H, H-100, OH), 5.22 (br. s, 2H, 2OH), 4.17 (br.d, 1H,
J = 10.0 Hz, H-6a00), 3.99–3.93 (dd, 1H, J = 10.0 Hz, J = 7.01 Hz, H-
6b00), 3.35–3.08 (m, 5H, H-200, H-300, H-400, H-500, OH), 1.99–1.93
(m, 2H, 2 ꢁ H-200), 1.27–0.95 (m, 19H, 9xCH2, OH), 0.83 (t, 3H,
J = 6.45 Hz, CH3); 13C NMR (DMSO-d6, 75 MHz): d 177.82 (CO),
172.90 (OCO), 164.64 (C-7), 161.74 (C-5), 156.84, 156.76 (C-2, C-
9), 148.95 (C-40), 145.28 (C-30), 133.44 (C-3), 121.89 (C-10),
121.51 (C-60), 116.57 (C-50), 115.54 (C-20), 104.29 (C-10), 101.11
(C-100), 99.11 (C-6), 93.89 (C-8), 76.74 (C-300), 74.60 (C-500), 74.37
(C-200), 70.54 (C-400), 63.36 (C-600), 33.66 (C-200), 31.80 (C-1000),
29.50, 29.35, 29.23, 29.01, 28.78 (C-400, C-500, C-600, C-700, C-800,
C-900), 24.68 (C-300), 22.59 (C-1100), 14.42 (C-1200).
3.1.11. (6-{[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-4H-chro-
men-3-yl]oxy}-4,5-dihydroxytet-rahydro-2H-pyran-2-yl)methyl
palmitate (12)
Yield: 93%; yellowish solid; Rf: 0.42 (acetone:toluene; 1:1: few
drops of AcOH); IR (KBr) cmꢀ1: 3455, 3273, 3077, 3007, 2925,
2854, 2546, 2244, 2136, 1981, 1837, 1765, 1657, 1457, 1364,
1306, 1203, 1165, 1053, 828, 737, 625; 1H NMR (DMSO-d6,
3.1.14. (6-{[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-
4Hchromen-3-yl]oxy}-3,4,5-trihydroxy-tetrahydro-2H-pyran-2-yl)
methyl (9Z,12Z)-9,12-octadecadienoate (15)
300 MHz):
d 12.62 (s, 1H, ArOH), 10.86 (br s, 1H, ArOH),
7.36–7.30 (m, 2H, H-20, H-60), 6.83 (br d, 1H, J = 8.64 Hz, H-50),
6.39 (d, 1H, J = 2.01 Hz, H-8), 6.19 (d, 1H, J = 2.01 Hz, H-6),
5.46–5.40 (m, 2H, H-100, OH), 5.22 (br. s, 2H, 2OH), 4.17 (br.d, 1H,
J = 10.1 Hz, H-6a00), 3.99–3.93 (dd, 1H, J = 10.1 Hz, J = 7.02 Hz, H-
6b00), 3.33–3.06 (m, 5H, H-200, H-300, H-400, H-500, OH), 1.99–1.93
(m, 2H, 2 ꢁ H-2000), 1.25–0.94 (m, 19H, 13 ꢁ CH2, OH), 0.83 (t, 3H,
J = 6.36 Hz, CH3); 13C NMR (DMSO-d6, 75 MHz): d 177.83 (CO),
172.89 (OCO), 164.65 (C-7), 161.75 (C-5), 156.84, 156.77 (C-2, C-
9), 148.95 (C-40), 145.29 (C-30), 133.45 (C-3), 121.88 (C-10),
121.51 (C-60), 116.58 (C-50), 115.54 (C-20), 104.29 (C-10), 101.13
(C-100), 99.10 (C-6), 93.88 (C-8), 76.75 (C-300), 74.61 (C-500), 74.38
(C-200), 70.53 (C-400), 63.37 (C-600), 33.66 (C-2000), 31.79 (C-10000),
29.57, 29.49, 29.36, 29.23, 29.03, 28.80 (C-4000, C-5000, C-6000, C-7000,
C-8000, C-9000, C-10000, C-11000, C-12000, C-13000), 24.69 (C-3000), 22.59
(C-15000), 14.40 (C-16000).
Yield: 91%; greenish yellow spongy solid; Rf: 0.59 (acetone:-
toluene; 1:1: few drops of AcOH); IR (KBr) cmꢀ1: 3346, 2946,
2835, 2492, 2181, 2043, 1897, 1762, 1643, 1591, 1466, 1447,
1230, 1027, 941, 737, 700; 1H NMR (DMSO-d6, 300 MHz): d
11.46–8.97 (br.s, 2H, ArOH), 7.58 (br s, 2H, H-20, H-60), 6.88 (br d,
1H, J = 6.9 Hz, H-50), 6.43 (s, 1H, H-8), 6.24 (s, 1H, H-6), 5.50–5.37
(m, 7H, H-9000, H-10000, H-12000, H-13000, H-100, 2OH), 4.22 (br.d, 1H,
J = 10.5 Hz, H-6a00), 4.02 (dd, 1H, J = 10.5 Hz, J = 7.2 Hz, H-6b00),
3.55–3.20 (m, 6H, H-200, H-300, H-400, H-500, 2 ꢁ OH), 2.78 (br s, 2H,
2 ꢁ H-11000), 2.16–2.04 (m, 6H, 2 ꢁ H-2000, 2 ꢁ H-8000, 2 ꢁ H-14000),
1.29–1.11 (m, 17H, 8xCH2, OH), 0.88 (br s, 3H, CH3); 13C NMR
(DMSO-d6, 75 MHz): d 178.12 (CO), 173.05 (OCO), 165.01 (C-7),
162.06 (C-5), 157.13 (C-2, C-9), 149.22 (C-40), 145.58 (C-30),
133.91 (C-3), 130.49 (C-9000, C-10000), 128.45 (C-12000, C-13000),122.17
(C-10), 121.93 (C-60), 116.96 (C-50), 115.89 (C-20), 104.65 (C-10),
101.64 (C-100), 99.43 (C-6), 94.19 (C-8), 77.22 (C-300), 74.99 (C-500),
74.77 (C-200), 70.98 (C-400), 63.75 (C-600), 33.96 (C-2000), 31.57
(C-16000), 29.66 (C-15000), 29.38 (C-7000), 29.16 (C-5000), 29.03 C-4000,
C-6000), 27.34 (C-8000, C-14000), 25.94 (C-11000), 24.91 (C-3000), 22.59
(C-17000), 14.48 (C-18000).
3.1.12. (6-{[2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-4-oxo-4Hchro-
men-3-yl]oxy}-4,5-dihydroxytet-rahydro-2H-pyran-2-yl)methyl
stearate (13)
Yield: 96%; greenish solid; Rf: 0.42 (acetone:toluene; 1:1: few
drops of AcOH); IR (KBr) cmꢀ1: 3449, 3271, 3070, 3007, 2926,
2854, 2559, 2250, 2124, 1997, 1830, 1767, 1655, 1454, 1366,
1308, 1203, 1172, 1057, 931, 822, 759, 731, 623; 1H NMR
(DMSO-d6, 300 MHz): d 10.63–8.98 (br.s, 2H, ArOH), 7.56 (br.s,
2H, H-20, H-60), 6.86 (br s, 1H, H-50), 6.41 (s, 1H, H-8), 6.22 (s, 1H,
H-6), 5.47–5.26 (m, 3H, H-100, 2OH), 4.20 (br.d, 1H, J = 10.5 Hz, H-
6a00), 4.00 (br s, 1H, H-6b00), 3.55–3.20 (m, 5H, H-200, H-300, H-400,
H-500, OH), 2.00 (br s, 2H, H-200, OH), 1.24–1.09 (m, 31H, 15 ꢁ CH2,
OH), 0.83 (br. s, 3H, CH3); 13C NMR (DMSO-d6, 75 MHz): d 178.14
(CO), 173.09 (OCO), 165.09 (C-7), 162.09 (C-5), 157.16 (C-2, C-9),
149.25 (C-40), 145.59 (C-30), 133.97 (C-3), 122.19 (C-10), 121.95
(C-60), 116.98 (C-50), 115.90 (C-20), 104.66 (C-10), 101.73 (C-100),
99.47 (C-6), 94.21 (C-8), 77.26 (C-300), 75.01 (C-500), 74.79 (C-200),
71.01 (C-400), 63.78 (C-600), 34.00 (C-2000), 31.99 (C-16000), 29.73
29.37, 29.23, 29.06 (C-4000, C-5000, C-6000, C-7000, C-8000, C-9000, C-10000,
Conflict of Interest
None of the authors have any competing interests in the
manuscript.
Acknowledgments
We are thankful to the financial support of the Discovery Grant
of Natural Sciences and Engineering Council (NSERC) of Canada and
the Atlantic Innovation Funds (AIF) program of the Atlantic Canada
Opportunities Agency (ACOA).

Ziaullah, H.P.V. Rupasinghe / Bioorganic Chemistry 65 (2016) 17–25
25
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