Naphthopyranone glycosides from Paepalanthus bromelioides

Article abstract of DOI:10.1016/S0031-9422(97)00952-7

Two new naphtho[2,3-C]pyran-1-one glycosides, paepalantine-9-O-β-D- glucopyranoside and paepalantine-9-O-β-D-allopyranosyl(1 → 6)glucopyranoside, were isolated from an ethanolic extract of capitula from Paepalanthus bromelioides and identified from their spectrometric data.

Full text of DOI:10.1016/S0031-9422(97)00952-7

Phytochemistry\ Vol[ 38\ No[ 0\ pp[ 196Ð109\ 0887
Þ 0887 Elsevier Science Ltd[ All rights reserved
Printed in Great Britain
Pergamon
\
9920Ð8311:87:,Ðsee front matter
PII] S9920Ð8311"86#99841Ð6
NAPHTHOPYRANONE GLYCOSIDES FROM PAEPALANTHUS
BROMELIOIDES
WAGNER VILEGAS\ꢀ LOURDES C[ SANTOS\ ALBERTO C[ ALEłCIO\ COSIMO PIZZA\$ SONIA PIACENTE\$
EDWIN DE PAUW% and PAULO T[ SANO&
Instituto de Qu(mica UNESP\ CP 244\ CEP 03799!899\ Araraquara\ SP\ Brazil^ $ Facolta de Farmacia\ Universita
ꢁ
Á
Á
degli Studi di Salerno\ 73973\ Penta\ Salerno\ Italy^ % Laboratoire de Spectrometrie de Masses\ Universite de
Á
Liege\ B5\ Sart Tilman\ Liege\ Belgium^ & Instituto de Biociencias\ Universidade de Sao Paulo\ 94497!899\ Sao Paulo\
Á
Á
¼
½
½
SP\ Brazil
"Received in revised form 7 September 0886#
Key Word Index*Paepalanthus bromelioides^ Eriocaulaceae^ naphthopyranone glycosides[
Abstract*Two new naphthoð1\2!CŁpyran!0!one glycosides\ paepalantine!8!O!b!D!glucopyranoside and pae!
palantine!8!O!b!D!allopyranosyl"0 : 5#glucopyranoside\ were isolated from an ethanolic extract of capitula
from Paepalanthus bromelioides and identi_ed from their spectrometric data[ Þ 0887 Elsevier Science Ltd[ All
rights reserved
INTRODUCTION
spots\ similar to that of paepalantine\ but with lower
Rf values[ The EtOH extract was then partitioned
between n!BuOH and water[ The layers were evap!
orated and then separately submitted to DCCC frac!
tionation a}ording 0 ð4Ł\ 1 and 2[ Characterization of
1 and 2 were relatively straightforward[ The spectral
data of both substances re~ected the similarities of
these structures with that of 0 "Tables 0 and 1#\ the
main di}erences being the sugar moieties\ present[
Compound 1 showed a yellowish!green spot on
TLC with an Rf value of 9[69 and was obtained sub!
sequently as a yellow amorphous powder[ The 02C
NMR and DEPT spectra exhibited 11 signals\ of
which six could be assigned to a glucopyranosyl moi!
ety ð7Ł[ The other 05 signals were similar to those of
The vegetation pattern found high in the Espinhacžo
chain in Brazil is classi_ed as {{campos rupestres||[
Plants grow either on stone or in sandy soils ð0Ł[ The
monocotyledoneous family Ericaulaceae grows wild
in this region and has ca 0199 species in 09Ð03 genera[
Paepalanthus is the largest genus of this family\ com!
prising ca 499 species ð1Ł[ It is primarily concentrated
in South America\ with few species in Central America
and two in Africa ð2Ł[ Many plants from this family are
called {{sempre!vivas|| "{{everlasting plants||#\ because
they still look alive years after being collected[ Only a
few studies on the chemical components of these spec!
ies have been performed ð3Ł[ A previous investigation
on P[ bromelioides demonstrated that the naphtho!
pyranone 0\ now named paepalantine\ is the main
constituent of the CHCl2 extract of the capitula and
has promising antibiotic activity against bacteria\ yea!
sts and dermatophytes ð4Ł[ More recently\ 0 also
showed strong cytotoxicity and mutageniticity ð5\ 6Ł[
Our interest in this type of compound has now led us
to investigate the EtOH extract of capitula from P[
bromelioides in the search for more polar compounds[
0
0 "Table 0#[ When compared with 0\ the H NMR
RESULTS AND DISCUSSION
Capitula were powdered and extracted successively
with hexane\ CH1Cl1\ EtOAc and EtOH[ TLC of the
EtOH extract revealed two pronounced yellow!green
ꢀ Author to whom correspondence should be addressed[
196

197
W[ VILEGAS et al[
Table 0[ 0H NMR assignments for compounds 0Ð2
H
0$
1%
2%
3
5[38 q "0[9#
5[53 s
5[43 s
5
7
00
OH!8
OH!09
OMe!4
2[73 s
5[75 d "1[4#
5[41 d "1[4#
1[12 d "0[9#
8[32 br s
02[11 br s
2[82 s
5[75 d "1[4#
5[85 d "1[4#
1[14 s
5[83 d "1[4#
5[75 d "1[4#
1[11 s
!
!
01[37 br s
2[68 s
2[89 s
01[36 br s
2[66s
OMe!6
2[81 s
Glucose
H0?
H1?
H2?
H3?
H4?
H5?
4[09 d "6[4#
2[2!2[8ꢀ
2[2!2[8ꢀ
2[2!2[8ꢀ
2[2!2[8ꢀ
2[2!2[8ꢀ
3[87 d "6[8#
2[31 dd "6[8^ 8[9#
2[29 dd "8[9^ 8[9#
2[15 dd "8[9^ 8[9#
2[54 m
3[91 dd "1[4^ 00[9#
2[50 dd "4[9^ 00[9#
Allose
H0ý
H1ý
H2ý
H3ý
H4ý
H5ý
3[40 d "6[3#
2[05 dd "6[3^ 1[4#
2[72 dd "1[4^ 3[9#
2[17 dd "3[9^ 8[1#
2[38 m
2[53 dd "2[9^ 01[9#
2[31 dd "4[9^ 01[9#
$ CDCl2^ % DMSO!d5^ ꢀ signal pattern unclear due to overlapping[
0
spectrum of 1 "Table 1# shows only the signal of a Assignments of the remaining H and 02C NMR sig!
chelated OH at d01[37 but not that at d8[32\ as occurs nals were based on 1D DFQ!COSY\ 0D HOHAHA
in 0\ thus suggesting that the glucose unity is linked and HSQC experiments[ The ES mass spectrum of 2
0
to position 8[ The anomeric signal in the H NMR showed an intense ðM¦NaŁ¦ ion at m:z 538 and a
spectra of 1 appeared at d4[96 "d\ J ꢂ 6[5 Hz#\ which smaller ðM¦HŁ ion at m:z 516[ The loss of the ter!
showed the b!con_guration of the sugar moiety[ The minal allose moiety was observed as the ðM−all¦HŁ¦
other signals were partly overlapped by the signals of ion at m:z 354 and the base peak resulted from the
OMe!4\ OMe!6 and DMSO[ ES mass spectrometry of protonated aglycone ðA¦HŁ¦ ion at m:z 292[ Thus\
1 exhibited a strong ðM¦NaŁ¦ ion at m:z 376\ the ion the structure of 2 was deduced as paepalantine!8!O!
ðM¦HŁ¦ at m:z 354\ the aglycone ion ðA¦HŁ¦ ion at b!D!allopyranosyl"0 : 5#!b!D!glycopyranoside[
m:z 292\ the adduct ðA¦NaŁ¦ at m:z 214 and a dimer
ð1M¦NaŁ¦ at m:z 840[ Thus\ 1 could be characterized acid hydrolysis followed by spectroscopic and TLC
as paepalantine!8!O!b!D!glucopyranoside[ comparison of the products[ As expected\ both sub!
The identity of 1 and 2 was further con_rmed by
Compound 2 also showed a yellowish!green spot stances a}orded 0 as the aglycone^ 0 furnished glucose
on TLC and on Rf of 9[39\ and was obtained as yellow and 1 furnished glucose and allose[
0
needles[ The NMR spectrum "Table 1# showed the
Naphthopyranones and their glycosides have hith!
broad singlet of a chelated OH at d 01[36\ thus indi! erto been isolated from the capitula of P[ bromelioides[
cating that the 09!OH is free and the sugar unity is Preliminary investigation showed that they occur also
bonded to OH!8\ as in 1[ Two anomeric proton signals in other species of this genus\ as well as in the scapes\
were also observed[ The two doublets appeared at d but not in the leaves[ The details of these investigations
3[87 "J ꢂ 6[8 Hz\ H0?\ glc# and d 3[40 "J ꢂ 6[3 Hz\ will be published later[
H0ý\ all#\ which showed the b con_guration in both
sugars[ The 02C NMR spectrum "Table 0# showed 17
EXPERIMENTAL
signals\ 05 of which were similar to those of 0[ The
remaining signals con_rmed the two anomeric car!
bons at d 090[9 and d 090[5[ The lack of signals in the
General
region of d 68!79 and the CH1 signal a d 57[7 clearly
NMR spectra of 1 were recorded at 199 MHz for
indicate that the two sugar units are 0 : 5 bonded[ 0H and 49 MHz for 02C in DMSO!d5[ NMR spectra

Naphthopyranone glycosides from Paepalanthus bromelioides
Table 1[ 02C NMR assignments for compounds 1 and 2[
198
The EtOH extract was concd "3[7 g# and partitioned
between n!BuOH and H1O[ The layers were separated
and concd[ The n!BuOH extract "1 g# was fractionated
by DCCC in CHCl2ÐMeOHÐH1O "02]6]3#"Solvent 0#\
descending[ Frs 0Ð09 a}orded 0 and frs 01Ð14 a}orded
pure 1[ The aq[ layer was fractionated by DCCC in
CHCl2ÐMeOHÐH1O"6]02]7#"Solvent 1#\ descending[
Frs 4Ð6 a}orded 19 mg of 0 frs 29Ð24 19 mg of pure
1 and frs 89Ð099 79 mg of pure 2[ TLC were carried
out on silica gel 59 "Merck# plates eluted with the
lower phase of solvent 0[
C
0$
1%
2%
0
2
3
056[7
041[3
88[1
055[5
041[7
87[4
055[8
041[3
87[2
3a
4
4a
5
011[3
039[4
024[8
82[5
012[0
027[7
024[6
83[2
012[2
028[9
024[8
83[7
6
7
8
8a
09
09a
052[3
090[8
047[6
097[5
047[1
85[6
050[6
090[8
047[3
098[6
048[3
86[3
050[2
091[1
047[3
098[7
048[5
86[4
Paepalantine!8!O!b!D!`lucopyranoside "1#[ Yellow
amorphous powder\ mp 080Ð081> "uncorr[#[ ða435
−199>\ ðaŁ467−094> "MeOH#[ UV l
142 "sh#\ 162 "3[54#\ 173 "3[56#\ 280 "2[60#^ ¦NaOH]
MeOH
nm "log o#]
max
152 "3[38#\ 172 "3[38#\ 289 "2[89#[ IR n cm−0] 2268
"br OH#\ 1819 "CH#\ 0571 "C1O#\ 0542 "C1C#\ 0506
"C1C#\ 0468 "C1C#\ 0359 "C1C#[ 0H and 02C NMR]
Tables 0 and 1[
KBr
max
00
OMe!4
OMe!6
08[5
50[6
44[4
07[8
50[5
44[3
08[9
50[2
44[3
Glucose
C0?
C1?
C2?
C3?
Paepalantine!8!O!b!D!allopyranosyl"0 : 5#`luco!
090[0
62[3
66[2
58[6
65[3
59[6
090[9
62[5
65[3
58[6
64[5
57[7
pyranoside "2#[ Yellow needles\ mp 035!036>
"uncorr[#[ ðaŁ435 −003>\ ðaŁ467 −65> "MeOH¦DMSO#[
UV lmMaexOH nm "log o#] 134 "sh#\ 162 "3[78#\ 173 "3[82#\
282 "2[86#^ ¦NaOH] 151 "3[61#\ 173 "3[63#\ 284 "3[03#[
C4?
C5?
KBr
IR n
cm−0]2274 "broad OH#\ 1803 "CH#\ 0570
max
"C1O#\ 0542 "C1C#\ 0479 "C1C#\ 0359 "C1C#[ 0H
and 02C NMR]Tables 0 and 1[
Allose
C0ý
C1ý
C2ý
C3ý
C4ý
C5ý
090[5
69[5
60[3
56[4
63[4
50[2
Acid hydrolysis of 1 and 2
A soln of 1Ð2 "each 09 mg# in 09) HCl was re~uxed
for 0 h[ The reaction mix[ was neutralized with 4)
NaOH and extracted with CHCl2[ The CHCl2 layer
was evapd to give 0\ identi_ed through TLC with an
authentic standard and 0H NMR[ The H1O layer was
evapd and tested by TLC with sugar standards\
a}ording glucose and allose[
$ CDCl2^ % DMSO!d5[
of 2 were recorded at 599 MHz for 0H and 049 MHz
for 02C in CD2OD[ Chemical shifts are given in d from
TMS[ DCCC was performed on a Tokyo Rikakikai
Co[ equipment with 299 columns of 1 mm id[ ES!
MS was performed on a quadrupole instrument and
samples were directly injected into the mass spec!
trometer via a Rheodyne injector[ MeCNÐH19 "0]0#
was used as the mobile phase[ N1 was used both as a
drying gas and for nebulization[
Acknowled`ements*We thank J[H[Y[ Vilegas and
Central Analitica do IQ!S\ Carlos!USP for recording
the UV spectra\ to FAPESP\ FUNDUNESP and to
CNPq for funding and fellowships to W[V[ and L[C[S[
REFERENCES
0[ Giulietti\ A[ M[ and Pirani\ J[ R[\ Workshop on
Neotropical Distribution Patterns\ Rio de Janeiro\
0877\ 28[
Plant material
Capitula of P[ bromelioides Silv[ were collected at 1[ Giulietti\ A[ M[ and Hensold\ N[\ Acta Botanica
¼
Serra do Cipo\ Minas Gerais\ Brazil[ A voucher speci!
Brasileira\ 0889\ 3\ 022[
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Powdered capitula "078 g# were successively
extracted with hexane\ CH1Cl1\ EtOAc and EtOH[

109
W[ VILEGAS et al[
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