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Matricarin-type guaianolides from Taraxacum bessarabicum and their chemotaxonomic significance
Biochemical Systematics and Ecology 34 (2006) 356e359 www.elsevier.com/locate/biochemsyseco
Matricarin-type guaianolides from Taraxacum bessarabicum and their chemotaxonomic significance Wanda Kisiel*, Klaudia Michalska Department of Phytochemistry, Institute of Pharmacology, Polish Academy of Sciences, 12 Sm˛etna Street, Pl-31-343 Krako´w, Poland Received 25 March 2005; accepted 10 September 2005
Keywords: Taraxacum bessarabicum; Asteraceae; Sesquiterpene lactones; Chemotaxonomy
1. Subject and source Roots of Taraxacum bessarabicum (Hornem.) Hand.-Mazz. were collected in July 2002 from plants growing in the Garden of Medicinal Plants, Institute of Pharmacology, Polish Academy of Sciences, Krako´w, where a voucher specimen (01/215) was deposited. Seeds of the plant collected in Russia (Volgograd Oblast, Hutor Mokrov, 70 m m.s.l.) were obtained from the Museum National d’Histoire Naturelle in Paris, France. 2. Previous work Previous chemical work on plants of the genus Taraxacum (Asteraceae, tribe Lactuceae) is poorly represented in the literature, however, sesquiterpene lactones, being present in at least 11 of the 13 species examined, seem to be useful taxonomic markers to separate different taxa of the genus (Zielin´ska and Kisiel, 2000; Michalska and Kisiel, 2004 and references cited herein). A number of eudesmane-, germacrane- and guaiane-type sesquiterpene lactones have been isolated that occur as aglycones and glycosides in root and aerial tissues of the plants. The most common sesquiterpene lactone is the germacranolide taraxinic acid b-glucopyranosyl ester found in eight species. More recently, matricarin-type 2-oxo-guaianolides, which are more unusual sesquiterpene lactones for this taxon, have been isolated from Taraxacum platycarpum (Cheong et al., 1998), Taraxacum obovatum (Michalska and Kisiel, 2003) and Taraxacum hondoense (Kisiel and Michalska, 2005). 3. Present study The present report deals with the isolation of nine sesquiterpene lactones (1e9, Glc ¼ b-glucopyranosyl), including a new natural product (1), and two phenolics from roots of the hitherto unstudied T. bessarabicum, a species mainly distributed in southeastern parts of Europe. * Corresponding author. Tel.: þ48 126623254; fax: þ48 126374500. E-mail address: [email protected] (W. Kisiel). 0305-1978/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.bse.2005.09.006
W. Kisiel, K. Michalska / Biochemical Systematics and Ecology 34 (2006) 356e359
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The dried and powdered plant material (55 g) was exhaustively extracted with ethanol at room temperature with shaking and the solvent was evaporated under reduced pressure to give a residue (10 g). This residue was subjected to column chromatography on silica gel (Merck, Art.7754) using hexaneeEtOAc, followed by EtOAceMeOH (up to 10% MeOH) gradient solvent systems, all fractions being monitored by TLC. The relevant fractions were combined and further separated by preparative TLC (Merck, Art. 5553) and semipreparative HPLC on a Delta-Pak C-18 column (particle size 15 mm, 25 100 mm) coupled to a photodiode array detector using H2OeMeOH mixtures at a flow rate of 3.0 ml min1. Elution of the silica gel column with hexaneeEtOAc (4:1) afforded 2 (1.2 mg), 5 (1.3 mg) and 6 (1.1 mg), after separation by preparative TLC (hexaneeEtOAc, 3:2) and semipreparative HPLC (H2OeMeOH, 1:1). Fractions eluted with hexaneeEtOAc (7:3), followed by preparative TLC (hexaneeEtOAc, 1:1) and semipreparative HPLC (H2OeMeOH, 3:2) purifications yielded 3 (12.5 mg). Fractions from EtOAc and EtOAceMeOH (19:1) elutions were further purified by preparative TLC (CHCl3eMeOH, 9:1 or 17:3). Initial EtOAc fractions gave pure 8 (9.9 mg) and a mixture of compounds which was processed by semipreparative HPLC (H2OeMeOH, 1:1) to give 4 (26.1 mg), an additional amount of 8 (6.5 mg) and 40 -hydroxyphenylacetic acid (2.9 mg). Repeated chromatography of further EtOAc fractions using semipreparative HPLC (H2OeMeOH, 13:7) furnished 1 (1.9 mg) and 9 (20.0 mg). A portion (21.1 mg) of EtOHeMeOH (19:1) fractions (57.9 mg) was processed by semipreparative HPLC (H2OeMeOH, 7:3) to give 7 (7.5 mg), an additional amount of 9 (2.3 mg) and dihydrosyringin (1.0 mg). OH
14
O
O
H 3
15
10 9
2
1 4 5
8 6
H
OR
OGlc
7 13
11
H O
O 12
O
O
2 R = Ac 3 R=H 4 R = Glc
1
OH
OH
H
H GlcO
H
X
O
H O
O
O
5 X = CH2 6 X = H, αMe
7 R
GlcO O O
8 R=H 9 R = OH
The previously known compounds were matricarin (2), deacetylmatricarin (3), its b-glucopyranoside (4), 9ahydroxy-3-deoxyzaluzanin C (5), its 11b,13-dihydroderivative (6), ixerin D (7), sonchuside A (8) cichorioside C (9), dihydrosyringin and 40 -hydroxyphenylacetic acid. Compounds 2 and 9, first reported from Chamomilla recutita and Cichorium intybus, respectively, were identified by comparison of their spectral data with those in the literature (Martinez et al., 1988; Seto et al., 1988). The remaining compounds were characterized by direct comparison (HPLC,
358
W. Kisiel, K. Michalska / Biochemical Systematics and Ecology 34 (2006) 356e359
1
H NMR and [a]D wherever possible) with compounds previously obtained from plants of the genus Taraxacum and some other members of the tribe Lactuceae in our earlier studies. Since no detailed 1H NMR data are available for 7 (Asada et al., 1984), they are added to Table 1. Compound 1 appeared to be a new natural product and a minor constituent of the plant material. Its structure was readily established when mass, 1H NMR, 1He1H COSY and NOESY spectra were directly compared with those of 4 (Michalska and Kisiel, 2003). The ESIMS provided an ion peak at m/z 443 [M þ H]þ consistent with the molecular formula of C21H30O10 which was 18 mass units higher than that of 4. The 1H NMR spectrum of 1 (Table 1) was similar to that of 4 but there were obvious differences suggesting the absence of the double bond between C-1 and C-10 and the presence of a tertiary-hydroxyl group at C-10 in 1. Thus, the Me-14 singlet (4: d 2.66) shifted upfield to d 1.60 and an additional one-proton doublet (H-1) at d 2.68 (J ¼ 6.9 Hz) appeared. At the same time, the H-6 resonance was notably deshielded (by 1.11 ppm) suggesting that the tertiary-hydroxyl group had a b-configuration (Gao et al., 1987; Sosa et al., 1989). The COSY spectrum confirmed all proton resonance assignments and the NOESY spectrum verified the proximities of H-7 to H-13 and H-9a, H-8 to H-6 and H-1 to H-9a and H-14. It also showed a cross peak between the anomeric sugar proton and H-8 of the aglycone confirming the attachment of the glucose moiety to the C-8 position. No distinct NOEs could be observed for H-5 and H-11 due to overlap but their a- and b-orientations, respectively, were assigned based on large coupling constant values of J5,6 ¼ 10.0 Hz and J7,11 ¼ 10.8 Hz. The similarities of the 1H NMR parameters of 1 and 4 appear to be an expression of their configurational and conformational relationships. Based on these data compound 1 was characterized as 10b-hydroxy-1a(10)-dihydrodeacetylmatricarin 8-O-b-glucopyranoside. 4. Chemotaxonomic significance Our chemical study of the roots of T. bessarabicum has led to the isolation of seven guaianolides (1e7) and two germacranolides (8, 9). This is the first time that compounds 2, 5, 6 and 9 have been isolated from Taraxacum species. Table 1 1 H (500.13 MHz) NMR data of 1 and 7 in pyridine-d5 Position Aglycone moiety 1 2a 2b 3 5 6 7 8a 8b 9a 9b 11 13 130 14 15 150 Glucosyl moiety 10 20 30 40 50 60 600
1, dH, J (Hz)
7, dH, J (Hz)
2.68 d (6.9) e e 6.08 dd (1.5, 1.5) 3.07e3.13 ma 4.71 dd (10.0, 10.0) 2.36 ddd (10.8, 10.0, 10.0) e 4.12 ddd (11.2, 10.0, 3.5) 1.81 dd (14.7, 11.2) 3.07e3.13 ma 3.07e3.13 ma 1.90 d (7.0)
2.41 2.49 2.19 4.90 2.97 4.48 3.37 2.19 1.24 1.69 1.90 e 6.20 5.33 1.30 5.47 5.74
1.60 s 2.16 br s
5.04 d (7.7) 4.05 t-like m 4.22e4.23 ma 4.22e4.23 ma 3.97 m 4.54 br d (11.6) 4.36 dd (11.6, 5.6)
The signal assignments were made from 1He1H COSY and NOESY spectra. a Signals overlapped. b Partially obscured by the signal of H2O.
ddd (9.7, 8.7, 8.0) ddd (13.3, 8.0, 8.0) ma mb br dd (10.0, 8.7) dd (10.0, 10.0) m ma m ddd (14.5, 6.0, 6.0) ddd (14.5, 8.5, 6.5) d (3.5) d (3.2) s br s br s
5.11 d (7.7) 4.09 dd (7.7, 7.0) 4.23e4.29 ma 4.23e4.29 ma 3.98 m 4.57 br d (11.3) 4.38 dd (11.3, 5.6)
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The guaianolides 5 and 6, involved in the allelopathic action of cultivar sunflowers (Macias et al., 1993), have also been found in Picris species of the tribe Lactuceae (Kisiel and Michalska, 2002). Although the occurrence of the germacranolide taraxinic acid b-glucopyranosyl ester is common and characteristic of Taraxacum species, the compound has not been found in the examined roots. The roots produce, similarly to T. platycarpum, T. obovatum and T. hondoense, matricarin-type guaianolide aglycones and glycosides. The aglycones, e.g. 2 and 3, are particularly characteristic for plants of the tribe Anthemideae of the Asteraceae, among the better known of which are the medicinal herbs C. recutita and Achillea millefolium (Seaman, 1982). The glycosides, including 4, have been found in T. obovatum, T. hondoense and T. bessarabicum. The guaianolides 3 and 4 co-occurring with the germacranolide 8 are major sesquiterpene lactone constituents of the three plant species. The appearance of matricarin-type guaianolides in Taraxacum species has no precedent although compound 3 and/or its 11,13-dehydro derivatives have been reported from Lactuca (Sessa et al., 2000) and Reichardia (Daniewski et al., 1988; Abdel-Mogib et al., 1993) species of the tribe Lactuceae. The existing chemical data suggest that sesquiterpene lactones may be used individually or in combination to authenticate Taraxacum species. Acknowledgement The authors wish to thank the State Committee for Scientific Research (KBN) of Poland for financial support (project: 2P05F 047 27). References Abdel-Mogib, M., Ayyad, S.N., Abou-Elzahab, M.M., Dawidar, A.M., 1993. Phytochemistry 34, 1434. Asada, H., Miyase, T., Fukushima, S., 1984. Chem. Pharm. Bull. 32, 3036. Cheong, H., Choi, E.J., Yoo, G.S., Kim, K.-M., Ryu, S.Y., 1998. Planta Med. 64, 577. Daniewski, W.M., Skibicki, P., Gumulka, M., Drozdz, B., Grabarczyk, H., Bloszyk, E., 1988. Acta Soc. Bot. Pol. 57, 539. Gao, F., Wang, H., Mabry, T.J., 1987. J. Nat. Prod. 50, 23. Kisiel, W., Michalska, K., 2002. Phytochemistry 61, 891. Kisiel, W., Michalska, K., 2005. Fitoterapia 76, 520. Macias, F.A., Varela, R.M., Torres, A., Molinillo, J.M.G., 1993. Phytochemistry 34, 669. Martinez, M.V., Munoz-Zamora, A., Joseph-Nathan, P., 1988. J. Nat. Prod. 51, 221. Michalska, K., Kisiel, W., 2003. Planta Med. 69, 181. Michalska, K., Kisiel, W., 2004. Biochem. Syst. Ecol. 32, 765. Seaman, F.C., 1982. Bot. Rev. 48, 121. Sessa, R.A., Bennett, M.H., Lewis, M.J., Mansfield, J.W., Beale, M.H., 2000. J. Biol. Chem. 275, 26877. Seto, M., Miyase, T., Umehara, K., Ueno, A., Hirano, Y., Otani, N., 1988. Chem. Pharm. Bull. 36, 2423. Sosa, V.E., Oberti, J.C., Gil, R.R., Ruveda, E.A., Goedken, V.L., Gutierez, A.B., Herz, W., 1989. Phytochemistry 28, 1925. Zielin´ska, K., Kisiel, W., 2000. Phytochemistry 54, 791.
Matricarin-type guaianolides from Taraxacum bessarabicum and their chemotaxonomic significance Wanda Kisiel*, Klaudia Michalska Department of Phytochemistry, Institute of Pharmacology, Polish Academy of Sciences, 12 Sm˛etna Street, Pl-31-343 Krako´w, Poland Received 25 March 2005; accepted 10 September 2005
Keywords: Taraxacum bessarabicum; Asteraceae; Sesquiterpene lactones; Chemotaxonomy
1. Subject and source Roots of Taraxacum bessarabicum (Hornem.) Hand.-Mazz. were collected in July 2002 from plants growing in the Garden of Medicinal Plants, Institute of Pharmacology, Polish Academy of Sciences, Krako´w, where a voucher specimen (01/215) was deposited. Seeds of the plant collected in Russia (Volgograd Oblast, Hutor Mokrov, 70 m m.s.l.) were obtained from the Museum National d’Histoire Naturelle in Paris, France. 2. Previous work Previous chemical work on plants of the genus Taraxacum (Asteraceae, tribe Lactuceae) is poorly represented in the literature, however, sesquiterpene lactones, being present in at least 11 of the 13 species examined, seem to be useful taxonomic markers to separate different taxa of the genus (Zielin´ska and Kisiel, 2000; Michalska and Kisiel, 2004 and references cited herein). A number of eudesmane-, germacrane- and guaiane-type sesquiterpene lactones have been isolated that occur as aglycones and glycosides in root and aerial tissues of the plants. The most common sesquiterpene lactone is the germacranolide taraxinic acid b-glucopyranosyl ester found in eight species. More recently, matricarin-type 2-oxo-guaianolides, which are more unusual sesquiterpene lactones for this taxon, have been isolated from Taraxacum platycarpum (Cheong et al., 1998), Taraxacum obovatum (Michalska and Kisiel, 2003) and Taraxacum hondoense (Kisiel and Michalska, 2005). 3. Present study The present report deals with the isolation of nine sesquiterpene lactones (1e9, Glc ¼ b-glucopyranosyl), including a new natural product (1), and two phenolics from roots of the hitherto unstudied T. bessarabicum, a species mainly distributed in southeastern parts of Europe. * Corresponding author. Tel.: þ48 126623254; fax: þ48 126374500. E-mail address: [email protected] (W. Kisiel). 0305-1978/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.bse.2005.09.006
W. Kisiel, K. Michalska / Biochemical Systematics and Ecology 34 (2006) 356e359
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The dried and powdered plant material (55 g) was exhaustively extracted with ethanol at room temperature with shaking and the solvent was evaporated under reduced pressure to give a residue (10 g). This residue was subjected to column chromatography on silica gel (Merck, Art.7754) using hexaneeEtOAc, followed by EtOAceMeOH (up to 10% MeOH) gradient solvent systems, all fractions being monitored by TLC. The relevant fractions were combined and further separated by preparative TLC (Merck, Art. 5553) and semipreparative HPLC on a Delta-Pak C-18 column (particle size 15 mm, 25 100 mm) coupled to a photodiode array detector using H2OeMeOH mixtures at a flow rate of 3.0 ml min1. Elution of the silica gel column with hexaneeEtOAc (4:1) afforded 2 (1.2 mg), 5 (1.3 mg) and 6 (1.1 mg), after separation by preparative TLC (hexaneeEtOAc, 3:2) and semipreparative HPLC (H2OeMeOH, 1:1). Fractions eluted with hexaneeEtOAc (7:3), followed by preparative TLC (hexaneeEtOAc, 1:1) and semipreparative HPLC (H2OeMeOH, 3:2) purifications yielded 3 (12.5 mg). Fractions from EtOAc and EtOAceMeOH (19:1) elutions were further purified by preparative TLC (CHCl3eMeOH, 9:1 or 17:3). Initial EtOAc fractions gave pure 8 (9.9 mg) and a mixture of compounds which was processed by semipreparative HPLC (H2OeMeOH, 1:1) to give 4 (26.1 mg), an additional amount of 8 (6.5 mg) and 40 -hydroxyphenylacetic acid (2.9 mg). Repeated chromatography of further EtOAc fractions using semipreparative HPLC (H2OeMeOH, 13:7) furnished 1 (1.9 mg) and 9 (20.0 mg). A portion (21.1 mg) of EtOHeMeOH (19:1) fractions (57.9 mg) was processed by semipreparative HPLC (H2OeMeOH, 7:3) to give 7 (7.5 mg), an additional amount of 9 (2.3 mg) and dihydrosyringin (1.0 mg). OH
14
O
O
H 3
15
10 9
2
1 4 5
8 6
H
OR
OGlc
7 13
11
H O
O 12
O
O
2 R = Ac 3 R=H 4 R = Glc
1
OH
OH
H
H GlcO
H
X
O
H O
O
O
5 X = CH2 6 X = H, αMe
7 R
GlcO O O
8 R=H 9 R = OH
The previously known compounds were matricarin (2), deacetylmatricarin (3), its b-glucopyranoside (4), 9ahydroxy-3-deoxyzaluzanin C (5), its 11b,13-dihydroderivative (6), ixerin D (7), sonchuside A (8) cichorioside C (9), dihydrosyringin and 40 -hydroxyphenylacetic acid. Compounds 2 and 9, first reported from Chamomilla recutita and Cichorium intybus, respectively, were identified by comparison of their spectral data with those in the literature (Martinez et al., 1988; Seto et al., 1988). The remaining compounds were characterized by direct comparison (HPLC,
358
W. Kisiel, K. Michalska / Biochemical Systematics and Ecology 34 (2006) 356e359
1
H NMR and [a]D wherever possible) with compounds previously obtained from plants of the genus Taraxacum and some other members of the tribe Lactuceae in our earlier studies. Since no detailed 1H NMR data are available for 7 (Asada et al., 1984), they are added to Table 1. Compound 1 appeared to be a new natural product and a minor constituent of the plant material. Its structure was readily established when mass, 1H NMR, 1He1H COSY and NOESY spectra were directly compared with those of 4 (Michalska and Kisiel, 2003). The ESIMS provided an ion peak at m/z 443 [M þ H]þ consistent with the molecular formula of C21H30O10 which was 18 mass units higher than that of 4. The 1H NMR spectrum of 1 (Table 1) was similar to that of 4 but there were obvious differences suggesting the absence of the double bond between C-1 and C-10 and the presence of a tertiary-hydroxyl group at C-10 in 1. Thus, the Me-14 singlet (4: d 2.66) shifted upfield to d 1.60 and an additional one-proton doublet (H-1) at d 2.68 (J ¼ 6.9 Hz) appeared. At the same time, the H-6 resonance was notably deshielded (by 1.11 ppm) suggesting that the tertiary-hydroxyl group had a b-configuration (Gao et al., 1987; Sosa et al., 1989). The COSY spectrum confirmed all proton resonance assignments and the NOESY spectrum verified the proximities of H-7 to H-13 and H-9a, H-8 to H-6 and H-1 to H-9a and H-14. It also showed a cross peak between the anomeric sugar proton and H-8 of the aglycone confirming the attachment of the glucose moiety to the C-8 position. No distinct NOEs could be observed for H-5 and H-11 due to overlap but their a- and b-orientations, respectively, were assigned based on large coupling constant values of J5,6 ¼ 10.0 Hz and J7,11 ¼ 10.8 Hz. The similarities of the 1H NMR parameters of 1 and 4 appear to be an expression of their configurational and conformational relationships. Based on these data compound 1 was characterized as 10b-hydroxy-1a(10)-dihydrodeacetylmatricarin 8-O-b-glucopyranoside. 4. Chemotaxonomic significance Our chemical study of the roots of T. bessarabicum has led to the isolation of seven guaianolides (1e7) and two germacranolides (8, 9). This is the first time that compounds 2, 5, 6 and 9 have been isolated from Taraxacum species. Table 1 1 H (500.13 MHz) NMR data of 1 and 7 in pyridine-d5 Position Aglycone moiety 1 2a 2b 3 5 6 7 8a 8b 9a 9b 11 13 130 14 15 150 Glucosyl moiety 10 20 30 40 50 60 600
1, dH, J (Hz)
7, dH, J (Hz)
2.68 d (6.9) e e 6.08 dd (1.5, 1.5) 3.07e3.13 ma 4.71 dd (10.0, 10.0) 2.36 ddd (10.8, 10.0, 10.0) e 4.12 ddd (11.2, 10.0, 3.5) 1.81 dd (14.7, 11.2) 3.07e3.13 ma 3.07e3.13 ma 1.90 d (7.0)
2.41 2.49 2.19 4.90 2.97 4.48 3.37 2.19 1.24 1.69 1.90 e 6.20 5.33 1.30 5.47 5.74
1.60 s 2.16 br s
5.04 d (7.7) 4.05 t-like m 4.22e4.23 ma 4.22e4.23 ma 3.97 m 4.54 br d (11.6) 4.36 dd (11.6, 5.6)
The signal assignments were made from 1He1H COSY and NOESY spectra. a Signals overlapped. b Partially obscured by the signal of H2O.
ddd (9.7, 8.7, 8.0) ddd (13.3, 8.0, 8.0) ma mb br dd (10.0, 8.7) dd (10.0, 10.0) m ma m ddd (14.5, 6.0, 6.0) ddd (14.5, 8.5, 6.5) d (3.5) d (3.2) s br s br s
5.11 d (7.7) 4.09 dd (7.7, 7.0) 4.23e4.29 ma 4.23e4.29 ma 3.98 m 4.57 br d (11.3) 4.38 dd (11.3, 5.6)
W. Kisiel, K. Michalska / Biochemical Systematics and Ecology 34 (2006) 356e359
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The guaianolides 5 and 6, involved in the allelopathic action of cultivar sunflowers (Macias et al., 1993), have also been found in Picris species of the tribe Lactuceae (Kisiel and Michalska, 2002). Although the occurrence of the germacranolide taraxinic acid b-glucopyranosyl ester is common and characteristic of Taraxacum species, the compound has not been found in the examined roots. The roots produce, similarly to T. platycarpum, T. obovatum and T. hondoense, matricarin-type guaianolide aglycones and glycosides. The aglycones, e.g. 2 and 3, are particularly characteristic for plants of the tribe Anthemideae of the Asteraceae, among the better known of which are the medicinal herbs C. recutita and Achillea millefolium (Seaman, 1982). The glycosides, including 4, have been found in T. obovatum, T. hondoense and T. bessarabicum. The guaianolides 3 and 4 co-occurring with the germacranolide 8 are major sesquiterpene lactone constituents of the three plant species. The appearance of matricarin-type guaianolides in Taraxacum species has no precedent although compound 3 and/or its 11,13-dehydro derivatives have been reported from Lactuca (Sessa et al., 2000) and Reichardia (Daniewski et al., 1988; Abdel-Mogib et al., 1993) species of the tribe Lactuceae. The existing chemical data suggest that sesquiterpene lactones may be used individually or in combination to authenticate Taraxacum species. Acknowledgement The authors wish to thank the State Committee for Scientific Research (KBN) of Poland for financial support (project: 2P05F 047 27). References Abdel-Mogib, M., Ayyad, S.N., Abou-Elzahab, M.M., Dawidar, A.M., 1993. Phytochemistry 34, 1434. Asada, H., Miyase, T., Fukushima, S., 1984. Chem. Pharm. Bull. 32, 3036. Cheong, H., Choi, E.J., Yoo, G.S., Kim, K.-M., Ryu, S.Y., 1998. Planta Med. 64, 577. Daniewski, W.M., Skibicki, P., Gumulka, M., Drozdz, B., Grabarczyk, H., Bloszyk, E., 1988. Acta Soc. Bot. Pol. 57, 539. Gao, F., Wang, H., Mabry, T.J., 1987. J. Nat. Prod. 50, 23. Kisiel, W., Michalska, K., 2002. Phytochemistry 61, 891. Kisiel, W., Michalska, K., 2005. Fitoterapia 76, 520. Macias, F.A., Varela, R.M., Torres, A., Molinillo, J.M.G., 1993. Phytochemistry 34, 669. Martinez, M.V., Munoz-Zamora, A., Joseph-Nathan, P., 1988. J. Nat. Prod. 51, 221. Michalska, K., Kisiel, W., 2003. Planta Med. 69, 181. Michalska, K., Kisiel, W., 2004. Biochem. Syst. Ecol. 32, 765. Seaman, F.C., 1982. Bot. Rev. 48, 121. Sessa, R.A., Bennett, M.H., Lewis, M.J., Mansfield, J.W., Beale, M.H., 2000. J. Biol. Chem. 275, 26877. Seto, M., Miyase, T., Umehara, K., Ueno, A., Hirano, Y., Otani, N., 1988. Chem. Pharm. Bull. 36, 2423. Sosa, V.E., Oberti, J.C., Gil, R.R., Ruveda, E.A., Goedken, V.L., Gutierez, A.B., Herz, W., 1989. Phytochemistry 28, 1925. Zielin´ska, K., Kisiel, W., 2000. Phytochemistry 54, 791.