Glucosides from MBOA and BOA detoxification by Zea mays and Portulaca oleracea

Article abstract of DOI:10.1021/np0580762

Incubation of Zea mays cv. Nicco seedlings with 6-methoxybenzoxazolin-2(3#) -one (MBOA) led to a minor detoxification product hitherto only found in Poaceae. This new compound was identified as 1-(2-hydroxy-4-methoxyphenylamino)- 1-deoxy-β-glucoside 1,2-c

Full text of DOI:10.1021/np0580762

34
J. Nat. Prod. 2006, 69, 34-37
Glucosides from MBOA and BOA Detoxification by Zea mays and Portulaca oleracea
Diana Hofmann,§ Mona Knop,† Huang Hao,†, Lothar Hennig,‡ Dieter Sicker,‡ and Margot Schulz*,†
Institut fu¨r Analytische Chemie, UniVersita¨t Leipzig, Linne´strasse 3, 04103 Leipzig, Germany, Institut fu¨r Molekulare Physiologie und
Biotechnologie der Pflanzen, UniVersita¨t Bonn, Karlrobert-Kreiten-Strasse 13, 53115 Bonn, Germany, and Institut fu¨r Organische Chemie,
UniVersita¨t Leipzig, Johannisallee 29, 04103 Leipzig, Germany
ReceiVed June 20, 2005
Incubation of Zea mays cv. Nicco seedlings with 6-methoxybenzoxazolin-2(3H)-one (MBOA) led to a minor detoxification
product hitherto only found in Poaceae. This new compound was identified as 1-(2-hydroxy-4-methoxyphenylamino)-
1-deoxy-â-glucoside 1,2-carbamate (1) (methoxy glucoside carbamate) and represents an analogue to the previously
described 1-(2-hydroxyphenylamino)-1-deoxy-â-glucoside 1,2-carbamate (glucoside carbamate) from benzoxazolin-
2(3H)-one (BOA). In Portulaca oleracea var. satiVa cv. Gelber treatment with BOA resulted in further unknown
detoxification products, which were not synthesized in detectable amounts after BOA absorption in all other species
tested. Compound 1 easily undergoes decay into BOA-5-O-glucoside (2). Z. mays seedlings, known to produce BOA-
6-O-Glc on incubation with BOA, are able to transform BOA-5-OH into BOA-5-O-glucoside (2). Besides the known
compounds, maize contained a formerly unseen product that accumulated during late stages of the detoxification process.
It was isolated and identified as 1-(2-hydroxyphenylamino)-6-O-malonyl-1-deoxy-â-glucoside 1,2-carbamate (3) (malonyl
glucoside carbamate).
Phytotoxic benzoxazolin-2(3H)-one (BOA) results from a two-
step degradation of the acetal glucoside (2R)-2-â-D-glucopyrano-
syloxy-4-hydroxy-2H-1,4-benzoxazin-3(4H)-one. These compounds
are secondary compounds in several species of the Acanthaceae,
Lamiaceae, Poaceae, Ranunculaceae, and Scrophulariaceae fami-
lies.1-5 Once released to the environment, BOA acts as an
allelochemical, causing dose-dependent growth inhibitions in di-
cotyledoneous and, to a smaller extent, in monocotyledoneous
species. Therefore, the compound was considered by agronomists
as a natural herbicide. However, about 30 tested plant species are
able to detoxify the compound and, in general, monocots with a
higher efficiency than dicots.6 Four detoxification products have
been characterized: 1-(2-hydroxyphenylamino)-1-deoxy-â-gluco-
side 1,2-carbamate (glucoside carbamate), gentiobioside carbamate,
BOA-6-OH (6-hydroxybenzoxazolin-2(3H)-one), and the corre-
sponding 6-â-O-glucoside.7,8 Glucosylation of BOA-6-OH is pos-
sible in all species tested, e.g., in Arabidopsis thaliana, where a
corresponding glucosyltransferase activity was upregulated during
BOA incubation. BOA-6-O-glucoside is the major product in
dicotyledoneous species, whereas nontoxic glucoside carbamate is
the major one in Poaceae. Gentiobioside carbamate production was
restricted to maize. This compound accumulates during the late
state of the detoxification process together with a new, hitherto
unseen, product very similar to glucoside carbamate.
metabolic flexibility and variability of higher plants in detoxification
of the allelochemically active compounds BOA and MBOA.
Results and Discussion
When maize seedlings were incubated with MBOA for 24 h,
large amounts of BOA-6-O-glucoside were found in the MeOH
extracts of the roots but only traces of a second product assigned
as 1-(2-hydroxy-4-methoxyphenylamino)-1-deoxy-â-glucoside 1,2-
carbamate (1) (methoxy glucoside carbamate). This compound
accumulated in higher concentrations when the incubation time was
extended to 48 h. It appeared only after MBOA incubations with
the tested cereals A. satiVa, H. Vulgare, and Z. mays, but not in A.
thaliana, Brassica oleracea, and other dicots tested.9 Compound 1
was isolated, purified, and subjected to structural analysis.
For solubility reasons, NMR data for glucoside 1 have been
1
recorded in CD3OD. The H NMR spectrum shows signals for a
1,2,4-trisubstituted phenyl ring and well-resolved signals in the
sugar region. In the 13C NMR spectrum the C-1′ resonance appears
at 84.6 ppm. The spectra are very similar to a carbamate derivative
described earlier.7 The complete assignment was made by use of
COSY, HMQC, and HMBC. Cross-peaks in the HMBC from H-1′
(5.25 ppm) to 70.1 (C-2′), 122.7 (C-1), and 154.7 ppm (NCOO)
caused by couplings via two and three bonds show the connection
with formation of the carbamate structure.
The CD3OD solution was directly introduced into the ESI-FT-
ICR-MS instrument. In the positive mode, an intensive peak at
351.09248 Da was observed, resulting from the monomer of
compound 1 containing one deuterium atom in the form of a sodium
adduct (exact theoretical mass 351.09146 Da) as well as a minor
peak at 352.09583 Da for the corresponding analogue with two
deuterium atoms. Mass analytical calculations gave rise to the
conclusion that the formula of the nondeuterated sodium-free
compound 1 is C14H17NO8.
The slower detoxification of MBOA to methoxy glucoside
carbamate (1) is in agreement with the known higher toxicity of
MBOA to both dicots and monocots, in comparison to BOA.
Whereas almost all of the dicotyledoneous weeds and crops tested
were able to perform BOA-N-glucosylation, at least in traces,
MBOA was only slowly converted in the Poaceae tested. The slower
conversion together with the accumulation of high amounts of still
toxic BOA-6-O-glucoside is assumed to be an important reason
for the higher toxicity of the methoxylated benzoxazolinone, also
for grasses.
Portulaca oleracea (Portulacaceae) was the only dicotyledoneous
species that accumulates new detoxification products resembling
the known BOA-6-OH compounds after BOA application.
Incubations with 6-methoxybenzoxazolin-2(3H)-one (MBOA)
also result in accumulation of BOA-6-O-glucoside.9 In Z. mays,
but also in Hordeum Vulgare and AVena satiVa roots, a second
product was found.
Here, three new glucosides from the detoxification of MBOA
and BOA by Z. mays and P. oleracea are described. The known
detoxification products together with the new ones demonstrate the
* To whom correspondence should be addressed. Tel: ++49 228
732151. Fax: ++49 228 731696. E-mail: ulp509@uni-bonn.de.
§ Institut fu¨r Analytische Chemie, Universita¨t Leipzig.
† Institut fu¨r Molekulare Physiologie und Biotechnologie der Pflanzen,
Universita¨t Bonn.
‡ Institut fu¨r Organische Chemie, Universita¨t Leipzig.
Present address: Chinese Academy of Science, Shanghai Institute of
Organic Chemistry, 354 Fenglin Rd., 25#, Shanghai 200032, China.
10.1021/np0580762 CCC: $33.50
© 2006 American Chemical Society and American Society of Pharmacognosy
Published on Web 01/07/2006

Glucosides from MBOA and BOA Detoxification
Journal of Natural Products, 2006, Vol. 69, No. 1 35
Extracts from BOA-incubated roots of P. oleracea contained
besides BOA-6-O-glucoside the new compound 2 and small
amounts of an additional, related detoxification product with a more
hydrophobic character. This compound was isolated from the extract
in microgram amounts only, allowing for an HRMS measurement
and some 600 MHz NMR data, but it was rather unstable and the
decay resulted in compound 2. A complete set of HRMS and NMR
spectra could be obtained, which allowed a structural assignation
as 5-â-D-glucopyranosyloxybenzoxazolin-2(3H)-one for 2 (BOA-
5-O-glucoside) as follows.
NMR investigations of a low-concentration sample of 2 have
been carried out in DMSO-d6 to identify also the OH protons of
the sugar moiety. The structural assignment was possible especially
by means of two-dimensional methods (COSY, HMQC, HMBC).
In the aromatic region of the proton spectrum three signals at 7.17
(d, 3J ) 8.7 Hz), 6.78 (d, 4J ) 2.4 Hz), and 6.75 ppm (dd, 3J ) 8.7
Hz, 4J ) 2.4 Hz) could be observed, showing the coupling pattern
of a 1,2,4-trisubstituted benzene derivative. The anomeric proton
of the sugar at 4.76 ppm gives a doublet with a coupling constant
of 7.6 Hz, which is typical for the axial position (â-configuration).
In the HMBC spectrum additionally a cross-peak from the anomeric
proton to a quaternary carbon at 155.1 ppm could be found, which
is caused by a three-bond coupling from the glucose to the aromatic
part of the heterocycle.
Figure 1. Detoxification products 1-3.
The NMR spectra of 3 in CD3OD showed signals that led to the
structural assignment shown in Figure 1. In the H spectrum of 3
1
a singlet at 3.35 ppm representing the CH2 group of the malonyl
unit was found close to the solvent signal. However, we could not
detect the corresponding carbon correlation cross-peak in the 2D
spectra. An explanation for this peculiar effect came from the NMR
investigation of a 6-O-malonyl-D-glucose sample, prepared as a
reference compound according to Kasai et al., which showed an
analogous behavior.11 Again, the methylene singlet appears at 3.35
ppm, whereas in the carbon spectrum only a very broad signal at
around 41.94 ppm could be observed. In both cases, this behavior
is caused by a slow H-D exchange of the acidic malonyl-methylene
The negative mode ESIMS of 2 with ammonia as buffer gave a
main peak at 312.07176 Da (exact theoretical mass 312.07249 Da).
In addition, a dimer signal at 625.15246 Da (exact theoretical mass
625.15226 Da) was found, and the mass analysis yields the formula
C13H14NO8 for the monomer peak, which leads to C13H15NO8 for
compound 2.
unit with the deuterated solvent causing line broadening: The 13
C
NMR spectra of 3 showed three carbonyl absorptions (170.19,
168.45 (typical for malonates), and 155.29). The HMBC spectrum
of 3 shows cross-peaks from H-1′ (d, 5.31 ppm) to the carbamate
CO at 155.29 ppm and from the diastereotopic 6′-OCH2 group (4.35
and 4.56 ppm) to the malonyl ester carbonyl group at 168.45 ppm.
Therefore, the carbonyl absorption at 170.19 ppm probably belongs
to the malonyl carboxy group.
HRESIMS spectra of glucoside 3 have been measured in CH3-
OH solution after NMR spectra have been recorded from the same
sample in CD3OD solution, which led to H-D exchange. Therefore,
these mass spectra showed several single peaks as well as peak
groups. No intensive peak resulting from a potential metabolite was
found in the low molecular range that corresponded to a dimer
signal. However, by using different buffers (MeOH-H2O-NH3,
MeOH-Et3N, MeOH-H2O-Et3N) one peak group (starting from
766 to 772 Da) in the molecular weight range of dimers was
persistent and increased with increasing base strength. By using
an NH3 buffer solution a second peak group starting from 787 to
791 Da was also found, due to the corresponding sodium adduct.
The mass analysis yields C32H31D2N2O20 and C32H30D2NaN2O20
for the two most intensive dimer peaks (767.17561 Da, exact mass
767.17577; 789.15811 Da, exact mass 789.15771 Da) of the
partially deuterated ions. Therefore, we postulate the formula
C16H17NO10 for the monomeric form of the metabolite. This is in
accordance with the structural proposal derived for 3 from the NMR
spectra. For the validation of the intrinsic nondeuterated pseudo-
molecular ion the solution was evaporated a second time and
redissolved in MeOH. The most intensive peaks are now 765.16262
Da (M - H)- (calcd 765.16322 Da) and 787.14655 Da (M + Na
- 2H)- (calcd 787.14516 Da).
Ensuing from the structural determination of 3 we believe that
the reported 6-O-oxalyl glucoside has instead to be regarded as a
malonyl derivative, also.12,13 In view of our findings, the reported
oxalyl derivative torachrysone 8-O-â-D-(6-oxalyl)glucopyranoside
is a malonyl derivative. Similarly to compound 3, two downfield
signals for carbonyl carbons (168.9 and 170.5 ppm in DMSO-d6)
were reported; however, no carbon for the CH2 unit was mentioned.
We assume that the same effect as with compound 3 has happened,
which “hides” this special carbon by proton exchange as a dynamic
effect. It is well known that oxalic acid monoester carbons have to
The structure of the unstable derivative of 2 mentioned above
may be a monoacetylated BOA-5-O-glucoside; however detailed
information on the position of acetylation is not possible. The
identity of compound 2 was further ascertained by assaying with
â-glucosidase from almonds. The enzymatic hydrolysis led to an
aglycone identical with 5-hydroxybenzoxazolin-2(3H)-one (BOA-
5-OH), which was synthesized as a reference and substrate in three
steps from 2-nitrophenol, as reported below.
Incubations of maize seedlings and P. oleracea plants with BOA-
5-OH were performed to complete the study. Both species absorbed
the compound, and in the root extracts BOA-5-O-glucoside was
detected. In maize, however, no further metabolite could be found.
As a final check, the product 2 was isolated from maize incubated
with BOA-5-OH and used for a full structural analysis by means
of NMR and HRMS. Thus, P. oleracea when incubated with BOA
produces via BOA-5-OH the BOA-5-O-glucoside 2, which is further
modified.
Maize is able to synthesize BOA-5-O-glucoside 2, also, but the
detoxification pathway via BOA-5-OH is not realized in vivo.
Instead, BOA-6-O-glucoside and glucoside carbamate production
is favored, with the latter accumulating in micromole amounts when
the plants are incubated in the presence of 500 µmol of BOA for
24 h. The use of an analytical Nucleodur 100-5 C18 HPLC column,
however, revealed a further detoxification product, 1-(2-hydroxy-
phenylamino)-6-O-malonyl-1-deoxy-â-glucoside 1,2-carbamate (3)
(malonyl glucoside carbamate), which is present in traces after 24
h but became a major product after at least 48 h of incubation.
Compound 3 has a UV spectrum similar to that of BOA and
glucoside carbamate and eluted only 1.5 min earlier than BOA.
For these reasons it had been overlooked in former studies where
HPLC runs with extracts from roots incubated for 24 h were
performed only with an analytical ultrasphere ODS RP 18 column,
where the new compound 3 coeluted with BOA. In subsequent
studies compound 3 was found in the highest concentration in the
100.000 g supernatant prepared according to Matsushima et al.10
It was isolated from the supernatant and subjected to structural
analysis.

36 Journal of Natural Products, 2006, Vol. 69, No. 1
Hofmann et al.
Synthesis of 5-Hydroxybenzoxazolin-2(3H)-one. 5-Hydroxyben-
zoxazolin-2(3H)-one was synthesized starting from 2-nitrophenol, which
was oxidized with alkaline ammonium persulfate to form 2-nitrohy-
droquinone in 35% yield according to the literature.20 Hydrogenation
of this compound in diluted HCl under normal pressure over Pd-C
followed by filtration and complete removal of the solvent by
lyophilization led to a pale greenish powder of 2-aminohydroquinone
hydrochloride (mp 202-205 °C). This salt was heated together with
urea at 145 °C for 3 h following the method reported21 to yield black
crystals of crude BOA-5-OH (mp 205-211 °C). Both recrystallization
and column chromatography did not result in BOA-5-OH pure enough
for the incubation studies. Eventually, sublimation of 250 mg of crude
product at 3 mbar in a silicon oil bath at 205 °C afforded a pure 100
mg sample of colorless BOA-5-OH (mp 218-218.5 °C, lit. Zinner et
al. 209-210 °C): 1H NMR (DMSO-d6) δ 11.29 (s, 1H, OH), 9.41 (s
1H, NH), 7.07 (d, 1H, JH-7,H-6 ) 8,7 Hz, H-7), 6.50 (d, 1H, JH-6,H-4
) 2.1 Hz, H-4), 6.45 (dd, 1H, H-6); 13C NMR (DMSO-d6) δ 155.1
(C-2), 154.2. (C-5), 136.4 (C-7a), 131.0 (C-3a), 109.9 (C-4), 108.0 (C-
7), 97.4 (C-6). These spectra have been measured with a Gemini 300BB
spectrometer.
be expected at about 160 ppm, whereas the carbonyl shifts for
malonic acid monoesters are expected distinctively downfield at
about 170 ppm.
Malonylation is a common step in higher plant detoxification
strategies. More than 175 6-O-malonylated glucosides have been
reported as natural products. For instance, 2,4-dichlorophenoxy-
acetic acid or dichloroaniline accumulates as a malonyl gluco-
side.14,15 An elusive indigo precursor in Isatis tinctoria has been
shown to be a malonyl glycoside of 3-hydroxyindole.16 Recently,
an acyltransferase from tobacco cells has been characterized that
catalyzes malonic acid transfer to exogenous flavonoid- and
naphthol-glycosides.17 The modification facilitates or manages the
transport of already glucosylated secondary compounds or xeno-
biotics by ATP-binding cassette transporters to target compartments,
such as the vacuole.18 Malonylation of glucoside carbamate may
facilitate the transport into the vacuole. As maize roots exude at
least a part of the detoxification products and no extractable
detoxification product is detectable in the plants a few days after
exposure to BOA,7 it is also possible that malonylation is involved
in the transfer into the apoplastic space.
1-(2-Hydroxy-4-methoxyphenylamino)-1-deoxy-â-D-glucoside 1,2-
1
3
carbamate (1): H NMR (CD3OD, H,H-COSY) δ 7.24 (d, J ) 8.7
4
3
Hz, 1H, H-6), 6.94 (d, J ) 2.4 Hz, 1H, H-3), 6.79 (dd, J ) 8.7 Hz,
Experimental Section
4J ) 2.4 Hz, 1H, H-5), 5.25 (d, 3J ) 9.3 Hz, 1H, H-1′), 4.00 (dd, 3J )
3
2
3
General Experimental Procedures. Caryopses of Z. mays L. were
aeroponically grown on cheesecloth for 5 days. Seeds of P. oleracea
were grown under field conditions for 6 weeks. The plants were
carefully harvested, cleaned from soil particles, and washed until
material adhering to the roots was completely removed. Maize seedlings
and Portulaca plants were incubated with 250 mL of medium containing
either 500 µM BOA, 250 µM MBOA, or 100 µM BOH-5-OH for 48
h. The medium was prepared as described by Schulz and Wieland.6
After incubation the roots were extracted with 50% MeOH. The extracts
were centrifuged for 15 min at 10.000g and the supernatants used for
HPLC analysis. HPLC was performed with a Beckman Coulter model
126 chromatograph equipped with a diode array detector and an
analytical ultrasphere ODS RP 18 column (Beckman Coulter). Elution
of the compounds was done with a gradient described in Wieland et
al.19 The new detoxification products (300-400 µg) with retention times
of 19 min (for 2) and 27 min were collected during 30-40 HPLC runs.
The corresponding fractions were combined and evaporated to dryness,
and the residues were dissolved in MeOH to check the purity by HPLC.
The remaining solutions were dried by vacuum centrifugation at 4 °C.
The residues were used for structural analyses. â-Glucosidase from
almonds (Sigma) was used for enzymatic hydrolysis of the glucose
moiety from BOA-5-O-glucoside 2. Enzyme activity was assayed with
acetate buffer pH 5.5 at 30 °C for 15 min. The assays were stopped by
boiling for 5 min, centrifuged, and checked for the product BOA-5-
OH by HPLC. Compound 3 was isolated from a 100.000g supernatant
obtained by the procedure described by Matsushima et al.10 Maize roots
(4 g) harvested from BOA incubated plants (500 µM BOA, 48 h) were
chopped with a razor blade in chopping buffer (50 mM Hepes pH 7.5,
5 mM EDTA, 0.4 M sucrose, 100 µL of protease inhibitor cocktail
(Sigma)). The chopped material was filtered though Miracloth (Cal-
biochem) and centrifuged twice at 1.000g and then at 8.000g prior to
the final centrifugation at 100.000g for 1 h at 4 °C. The resulting
supernatant was extracted with EtOAc, the aqueous phase was
evaporated in a vacuum centrifuge to dryness, and the residue was
dissolved in 50% MeOH. The procedure was repeated four times. From
the combined MeOH solutions compound 3 was isolated by 50 HPLC
runs using an analytical Nucleodur 100-5 C18 column (Macherey &
Nagel) and the gradient described above. Fractions containing the
compound were combined and evaporated to dryness, yielding about
0.5 mg of compound 3.
9.3 Hz, J ) 9.0 Hz, 1H, H-2′), 3.90 (dd, J ) 12.2 Hz, J ) 1.9 Hz,
1H, H-6′a), 3.80 (s, 3H, OCH3), 3.71 (dd, 2J ) 12.2 Hz, 3J ) 5.7 Hz,
3
3
1H, H-6′b), 3.53 (dd, J ) 9.3 Hz, J ) 9.0 Hz, 1H, H-3′), 3.51 (m,
1H, H-5′), 3.47 (dd, J ) 9.3 Hz, J ) 9.1 Hz, 1H, H-4′); 13C NMR
(CD3OD, HMQC, HMBC) δ 157.0 (C-4), 154.7 (NCOO), 143.8 (C-
2), 122.7 (C-1), 111.8 (C-6), 109.6 (C-5), 97.1 (C-3), 84.6 (C-1′), 80.1
(C-5′), 77.7 (C-3′), 70.3 (C-4′), 70.1(C-2′), 61.7 (C-6′) 55.4 (OCH3).
3
3
1
5-â-D-Glucopyranosyloxybenzoxazolin-2(3H)-one (2): H NMR
(DMSO-d6, H,H-COSY) δ 7.17 (d, 3J ) 8.7 Hz, 1H, H-7), 6.78 (d, 4J
3
4
) 2.4 Hz, 1H, H-4), 6.75 (dd, J ) 8.7 Hz, J ) 2.4 Hz, 1H, H-6),
3
3
6.63 (brs), 1H, NH), 5.28 (d, J ) 4.9 Hz, 1H, 2′-OH), 5.05 (d, J )
3
3
4.7 Hz, 1H, 3′-OH), 4.99 (d, J ) 5.3 Hz, 1H, 4′-OH), 4.76 (d, J )
7.6 Hz, 1H, H-1′), 4.57 (t, 3J ) 5.7 Hz, 1H, 6′-OH), 3.69 (1H, H-6′a),
3.46 (1H, H-6′b), 3.29 (m, 1H, H-5′), 3.25 (m, 1H, H-3′), 3.21 (m, 1H,
H-2′), 3.14 (m, 1H, H-4′); 13C NMR (DMSO-d6, HMQC, HMBC) δ
155.4 (HNCOO), 155.1 (C-5), 139.2 (C-7a), 131,8 (C-3a), 110.7 (C-
6), 110.5 (C-7), 102.6 (C-1′), 100.1 (C-4), 77.9 (C-5′), 77.3 (C-3′),
74.1 (C-2′), 70.6 (C-4′), 61.6 (C-6′).
1-(2-Hydroxyphenylamino)-6-O-malonyl-1-deoxy-â-D-glucoside
1
3
1,2-carbamate (3): H NMR (CD3OD, H,H-COSY) δ 7.34 (d, J )
3
3
7.3 Hz, 1H, H-6), 7.26 (d, J ) 7.8 Hz, 1H, H-3), 7.23 (dd, J ) 7.3
4
3
4
Hz, J ) 1.0 Hz, 1H, H-5), 7.18 (dd, J ) 7.8 Hz, J ) 1.0 Hz, 1H,
H-4), 5.31 (d, 3J ) 9.3 Hz, 1H, H-1′), 4.56 (dd, 2J ) 12.1 Hz, 3J ) 2.1
Hz, 1H, H-6′a), 4.35 (dd, 2J ) 12.1 Hz, 3J ) 5.2 Hz, 1H, H-6′b), 4.00
(dd, 3J ) 9.3 Hz, 3J ) 9.0 Hz, 1H, H-2′), 3.75 (m, 1H, H-5′), 3.56 (m,
1H, H-3′), 3.56 (m, 1H, H-4′), 3.35 (s, 2H, CH2); 13C NMR (CD3OD,
HMQC, HMBC) δ 170.10 (COOH), 168.45 (COOCH2), 155.29
(NCOO), 144.08 (C-2), 130.18 (C-1), 125.23 (C-5), 124.06 (C-4),
112.61 (C-6), 110.85 (C-3), 85.50 (C-1′), 78.25 (C-3′), 78.09 (C-5′),
71.01 (C-4′), 70.89 (C-2′), 65.06 (C-6′), 40.42 broad, weak (HOOC-
CH2-CO-).
Acknowledgment. H.H. thanks the Alexander von Humboldt
Foundation for a fellowship supporting research at the Universities of
Leipzig and Bonn.
References and Notes
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NMR spectra for the detoxification products 1 and 2 were recorded
on a Bruker DRX-600 spectrometer (1H: 600 MHz, 13C: 150 MHz).
NMR spectra for 3 were measured on a Bruker DRX-700 Avance
spectrometer (1H: 700 MHz, 13C: 175 MHz). Chemical shifts are
reported in ppm; the signals of CD3OD (1H: δ ) 3.31 ppm; 13C: δ )
49.00 ppm) and DMSO-d6 (1H: δ ) 2.50 ppm; 13C: δ ) 39.52 ppm)
were used as internal references. HRESIMS spectra were recorded with
syringe infusion with a Bruker FT-ICR mass spectrometer APEX II,
equipped with a 7 T magnet.

Glucosides from MBOA and BOA Detoxification
Journal of Natural Products, 2006, Vol. 69, No. 1 37
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