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A secolignan from Peperomia glabella
Pergamon
Phytochemistry, Vol. 43, No. 5. pp. 1097-1098, 1996 Copyright © 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0031-9422/96 $15.00 + 0.00
PII: S0031-9422(96)00449-9
A SECOLIGNAN FROM PEPEROMIA GLABELLA FRANCO DELLE MONACHE* and REINALDOS. COMPAGNONEt Centro di Chimica dei Recettori del CNR., Universit/t Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Roma, Italy tCentro de Quimica Organica, Escuela de Quimica, Facultad de Ciencias, Universidad Central de Venezuela, Apartado 47102, Caracas, Venezuela
((Received in revisedform 16 May 1996)) Key Word Index--Peperomia glabella; Piperaceae; secolignan; peperomin D; 2D NMR.
Abstract--An unusual secolignan (peperomin D) has been isolated from Peperomia glabella. Its structure was determined by high-field two-dimensional NMR spectroscopy. Copyright © 1996 Elsevier Science Ltd
INTRODUCTION
Peperomia glabella is an epiphyte used in Venezuelan folk medicine as an antiasthmatic [1]; no previous phytochemical study is reported for this species. Fractionation of the methanolic extract of the whole plant led to the isolation of a compound which was named peperomin D and assigned structure 1. Peperomin D belongs to a rare type of secolignans, of which only three similar compounds have been previously reported in the literature [2].
R E S U L T S AND D I S C U S S I O N
Peperomin D, C 2 o H 1 8 0 6 , w a s obtained as a crystalline dextrorotatory solid showing strong absorption at 1765 cm -~ in its IR spectrum and a base peak 2 at m/z 255 in the mass spectrum, attributable to y butyrolactone and a doubly piperonylic carbocation, respectively. This was corroborated by the ~3C NMR spectrum which exhibited a signal at 6 179.7 and two sets of signals in the range 6 148.2-101.2. The non-equivalence of the piperonylic residues was also evident in the ~H NMR signals for the two methylenedioxy groups, which appeared as a singlet and a quartet (J = 1.4 Hz), respectively. In combination with appropriate spin-decoupling experiments and HETCOR spectra, the results from INEPT experiments [3, 4] permitted the unambiguous assignment of the NMR data, (Table 1). In particular, in the INEPT experiments, selective irradiation of Me-6 (6 0.91) enhanced the carbonyl resonance at 6 179.7 and the C-3 signal (6 47.2); selective irradiation of the methylene protons gave a response
with the carbonyl resonance and the doubly benzylic C-5 (6 55.6). On the basis of our results (Table 1), previous assignments for C-2 and C-3 of peperomins (3) A (R, R 1 = R 2, R 3 = methylenedioxy), B (R, R1= methylenedioxy; R 2 = R 3 = OMe) and C (R = R I = R 2 = R 3 = OMe) [2] should be reversed.
EXPERIMENTAL
Plant material. Peperomia glabella (Sw.) A. Dieter, popular name 'Salvaje', was collected near Caracas and identified by Dr T. Lasser, Instituto de Botanica, Ministerio de Agricultura y Cria de la Republica de Venezuela, where a voucher sample is deposited.
O
or
O
'5
1 /---'O
OMe OMe
*Author to whom co~espondence should be add~ssed.
2 1097
3
R3
1098
F. DELLEMONACHEand R. S. COMPAGNONE Table 1. NMR data of peperomin D Connected carbon* Position
8c
1 2 3 4
179.7 40.3 47.2 70.4
5 6 1', 1" 2', 2" 3', 3" 4', 4" 5', 5" 6', 6" O-CH2-O
55.6 15.7 136.2, 135.6 107.7, 107.6 146.6 148.2, 148.1 108.6 108.5 120.7, 120.3 101.1
8H
2j
3j
2.35 sex 2.89 dq 4.31 dd (9.5, 7.5) 3.79 dd (9.5, 8.0) 3.65 d (11.5) 0.91 dd (7.2)
C-I, C-3, C-6
C-5 C-6 C-1,C-5
C-I',C-I" C-2
C-2', C-2", C-6', C-6", C-I, C-3
t f 5.93 s 5.92 q (1.4)
*INEPT experiments. tOvedapped (8 6.74-6.71).
Extraction and purification. The whole plant (70 g) was extracted with MeOH ( x 3 ) and the residue partitioned between H20 and EtOAc. The residue (250 g) from the organic phase was fractioned by CC on silica gel (Benzene-EtOAc, 19:1) to yield mixt. of fatty acid Me esters (mainly Melinoleate) and raw peperomin D (1; 80 mg). Final purification was performed by re-crystallization Peperomin D, (1). Mp. 122-124 ° (heptane). [C~]D+ CHCI3 23 (c 0.1 CHC13). IR Z'ma x cm - l . 1765. 1H (300 MHz) and 13C (75 MHz) (CDC13) in Table 1. El-MS (probe) 70 eV, m/z (rel. int.): 354 [M] + (64), 255 [CH-Pip2] + (100), 225 (12), 197 (72), 195 (78), 167 (13), 139 (61), 127.5 [M] ++ (15), 127 (20), 115 (11), 91 (5).
Acknowledgment--Tiffs work was supported by an agreement between CNR (Italy) and CONICIT (Venezuela).
REFERENCES
1. Velez Salas, F. (1982) in Plantas Medicinales de Venezuela (Velez Boza, F., ed.). INAGRO, Caracas, p. 255. 2. Chen, C.-M., Jan, F.-Y, Chen, M.-T. and Lee, T.-J. (1989) Heterocycles 29, 411. 3. Bax, A. (1984) J. Magn. Res. 57, 314. 4. Radics, L. and Sandor, P. (1988) Magn. Moments 3,2.
Phytochemistry, Vol. 43, No. 5. pp. 1097-1098, 1996 Copyright © 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 0031-9422/96 $15.00 + 0.00
PII: S0031-9422(96)00449-9
A SECOLIGNAN FROM PEPEROMIA GLABELLA FRANCO DELLE MONACHE* and REINALDOS. COMPAGNONEt Centro di Chimica dei Recettori del CNR., Universit/t Cattolica del Sacro Cuore, Largo F. Vito 1, 00168 Roma, Italy tCentro de Quimica Organica, Escuela de Quimica, Facultad de Ciencias, Universidad Central de Venezuela, Apartado 47102, Caracas, Venezuela
((Received in revisedform 16 May 1996)) Key Word Index--Peperomia glabella; Piperaceae; secolignan; peperomin D; 2D NMR.
Abstract--An unusual secolignan (peperomin D) has been isolated from Peperomia glabella. Its structure was determined by high-field two-dimensional NMR spectroscopy. Copyright © 1996 Elsevier Science Ltd
INTRODUCTION
Peperomia glabella is an epiphyte used in Venezuelan folk medicine as an antiasthmatic [1]; no previous phytochemical study is reported for this species. Fractionation of the methanolic extract of the whole plant led to the isolation of a compound which was named peperomin D and assigned structure 1. Peperomin D belongs to a rare type of secolignans, of which only three similar compounds have been previously reported in the literature [2].
R E S U L T S AND D I S C U S S I O N
Peperomin D, C 2 o H 1 8 0 6 , w a s obtained as a crystalline dextrorotatory solid showing strong absorption at 1765 cm -~ in its IR spectrum and a base peak 2 at m/z 255 in the mass spectrum, attributable to y butyrolactone and a doubly piperonylic carbocation, respectively. This was corroborated by the ~3C NMR spectrum which exhibited a signal at 6 179.7 and two sets of signals in the range 6 148.2-101.2. The non-equivalence of the piperonylic residues was also evident in the ~H NMR signals for the two methylenedioxy groups, which appeared as a singlet and a quartet (J = 1.4 Hz), respectively. In combination with appropriate spin-decoupling experiments and HETCOR spectra, the results from INEPT experiments [3, 4] permitted the unambiguous assignment of the NMR data, (Table 1). In particular, in the INEPT experiments, selective irradiation of Me-6 (6 0.91) enhanced the carbonyl resonance at 6 179.7 and the C-3 signal (6 47.2); selective irradiation of the methylene protons gave a response
with the carbonyl resonance and the doubly benzylic C-5 (6 55.6). On the basis of our results (Table 1), previous assignments for C-2 and C-3 of peperomins (3) A (R, R 1 = R 2, R 3 = methylenedioxy), B (R, R1= methylenedioxy; R 2 = R 3 = OMe) and C (R = R I = R 2 = R 3 = OMe) [2] should be reversed.
EXPERIMENTAL
Plant material. Peperomia glabella (Sw.) A. Dieter, popular name 'Salvaje', was collected near Caracas and identified by Dr T. Lasser, Instituto de Botanica, Ministerio de Agricultura y Cria de la Republica de Venezuela, where a voucher sample is deposited.
O
or
O
'5
1 /---'O
OMe OMe
*Author to whom co~espondence should be add~ssed.
2 1097
3
R3
1098
F. DELLEMONACHEand R. S. COMPAGNONE Table 1. NMR data of peperomin D Connected carbon* Position
8c
1 2 3 4
179.7 40.3 47.2 70.4
5 6 1', 1" 2', 2" 3', 3" 4', 4" 5', 5" 6', 6" O-CH2-O
55.6 15.7 136.2, 135.6 107.7, 107.6 146.6 148.2, 148.1 108.6 108.5 120.7, 120.3 101.1
8H
2j
3j
2.35 sex 2.89 dq 4.31 dd (9.5, 7.5) 3.79 dd (9.5, 8.0) 3.65 d (11.5) 0.91 dd (7.2)
C-I, C-3, C-6
C-5 C-6 C-1,C-5
C-I',C-I" C-2
C-2', C-2", C-6', C-6", C-I, C-3
t f 5.93 s 5.92 q (1.4)
*INEPT experiments. tOvedapped (8 6.74-6.71).
Extraction and purification. The whole plant (70 g) was extracted with MeOH ( x 3 ) and the residue partitioned between H20 and EtOAc. The residue (250 g) from the organic phase was fractioned by CC on silica gel (Benzene-EtOAc, 19:1) to yield mixt. of fatty acid Me esters (mainly Melinoleate) and raw peperomin D (1; 80 mg). Final purification was performed by re-crystallization Peperomin D, (1). Mp. 122-124 ° (heptane). [C~]D+ CHCI3 23 (c 0.1 CHC13). IR Z'ma x cm - l . 1765. 1H (300 MHz) and 13C (75 MHz) (CDC13) in Table 1. El-MS (probe) 70 eV, m/z (rel. int.): 354 [M] + (64), 255 [CH-Pip2] + (100), 225 (12), 197 (72), 195 (78), 167 (13), 139 (61), 127.5 [M] ++ (15), 127 (20), 115 (11), 91 (5).
Acknowledgment--Tiffs work was supported by an agreement between CNR (Italy) and CONICIT (Venezuela).
REFERENCES
1. Velez Salas, F. (1982) in Plantas Medicinales de Venezuela (Velez Boza, F., ed.). INAGRO, Caracas, p. 255. 2. Chen, C.-M., Jan, F.-Y, Chen, M.-T. and Lee, T.-J. (1989) Heterocycles 29, 411. 3. Bax, A. (1984) J. Magn. Res. 57, 314. 4. Radics, L. and Sandor, P. (1988) Magn. Moments 3,2.