Isolation and identification of cytotoxic compounds from the rhizomes of Paris quadrifolia L.

Abstract

Background:

Paris quadrifolia L. is a medicinal plant which contains steroidal saponins. The present study reports isolation and structural identification of six pennogenyl saponins obtained from P. quadrifolia rhizomes. The four spirostan saponins were obtained from P. quadrifolia for the first time. The cytotoxic effects of the sub-fractions and six compounds isolated from the plant extract were evaluated on tumour cells.

Materials and Methods:

Ethanol extract from the rhizomes of P. quadrifolia were partinioned using column chromatography. The saponins were isolated from the obtained sub-fractions by isocratic RP HPLC and their structures were determined by means of 1D and 2D NMR spectroscopy and MALDI TOF MS. The cytotoxic effects of the sub-fractions and the isolated compounds were tested against human promyelocytic leukaemia cells (HL-60), human cervical adenocarcinoma cells (HeLa) and human breast cancer cells (MCF-7) using the [(3-(4,5-dimethylthiazol-2-yl)]-2,5-diphenyltetrazolium bromide (MTT) assay.

Results:

Six pennogenyl saponins were isolated from P. quadrifolia rhizomes: pennogenin 3-O-β-D-glucopyranoside (1), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (2), pennogenin 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (3), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (4), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (5), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (6). Pennogenyl saponins 5 and 6 exhibited cytotoxic activity against HL-60, HeLa and MCF-7 tumour cells with IC₅₀ values of 1.0 ± 0.04 μg/ml, 1.8 ± 0.072 μg/ml and 2.4 ± 0.096 μg/ml respectively, and 2.0 ± 0.08 μg/ml, 2.5 ± 0.125 μg/ml and 3.2 ± 0.128 μg/ml respectively.

Conclusion:

Compounds 1-4 were isolated from this species for the first time.

INTRODUCTION

The genus Paris (Melanthiaceae) includes 24 species of plants, which grow in an extensive area from Europe to Asia. Apart from the European Paris quadrifolia and the Caucasian P. incompleta, the other 22 species of Paris grow in western Asia, western Siberia and the Himalayas.[1] The plant occurs in deciduous forests in Poland and studies of this species are conducted at present.[2,3]

The Paris species contain a wide range of steroidal compounds which are potential cytotoxic agents. Many articles describe species of Paris widespread in the Far East as plants of traditional Chinese medicine. The objects of those studies were mainly P. polyphylla var. chinensis and P. polyphylla var. yunnanensis.[4,5,6,7,8]

In this work, we present isolation of six pennogenyl saponins from P. quadrifolia rhizomes and determination of their structures: pennogenin 3-O-β-D-glucopyranoside (1), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (2), pennogenin 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (3), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (4), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (5), pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (6). Earlier, these substances had been identified in other species of Paris[9,10,11] and other genera/species: Trillium,[12,13,14,15,16,17,18] Heloniopsis orientalis,[19,20] Polygonatum kingianum,[21] Trachycarpus wagnerianus,[22] Dioscorea,[23,24] Triteleia lactea,[25] Majanthemum dilatatum,[26] Ophiopogon japonicus,[27] Dracaena mannii,[28] Ypsilandra thibetica.[29] But the six saponins mentioned above have not been isolated at the same time from one species of Paris. Except saponins 5 and 6,[30,31] the spirostan saponins 1, 2, 3, 4 from P. quadrifolia rhizomes were obtained from this plant for the first time.

The cytotoxic effects of fractions obtained from P. quadrifolia extract and the six mentioned compounds were examined in vitro on HL-60, HeLa and MCF-7 tumour cells. Saponins 5 and 6 showed significant cytotoxic activity against the cells.

MATERIALS AND METHODS

General experimental procedures

Column chromatography was performed on a column (35 × 4.8 cm) with silica gel (Kieselgel 60; 0.05-0.2 mm; Macherey-Nagel). Thin layer chromatography (TLC) was carried out on precoated Kieselgel 60 (Merck). Semi-preparative high-performance liquid chromatography (HPLC), isocratic separations were run with the use of a Gradient Pump (Pharmacia LKB), Econosil C18 column (250 × 10 mm; 10 μm; Alltech) connected to a VYDAC C18 guard column; KNAUER injector with a loop of 200 μl. The elution profile was monitored with a differential refraction detector RIDK 102 (Laboratorni Pristroje Praha).

D and L configurations of sugar components were assigned as previously described.[32,33,34]

Gas liquid chromatography (GLC) analyses were performed on a TOP GC 8000 (CE Instruments) gas chromatograph equipped with a flame ionization detector (FID) and a DB-23 fused-silica capillary column (60 m, 0.3 mm I.D., 0.15 μm film thickness, JandW scientific).

Mass spectra of all saponins were recorded in ethanol solutions on a Bruker BIFLEX III MALDI TOF mass spectrometer equipped with a nitrogen laser (λ = 337 nm) in a DHB matrix (2,5-dihydroxybenzoic acid). The spectra were recorded in positive mode in range of m/z 400-2500 amu (averages of 250 to 450 acquisitions) with a pulse width of 3ns, and an energy density of 10⁶ to 10⁷ W cm^-2. A mixture of peptides was used as the calibration standard. All nuclear magnetic resonance (NMR) spectra were acquired on a Bruker Avance III 700 MHz spectrometer at 27°C in C₆D₅N, and calibrated according to Transcranial magnetic stimulation tetramethylsilane (TMS).

Plant material

P. quadrifolia L. was collected at Gdańsk (Poland, 54° 21’69”N, 18° 33’24”E). The fresh rhizomes of the plant were dried at room temperature. A voucher specimen has been deposited in the Herbarium of the Medical University of Gdańsk (GDMA herbarium).

Extraction and isolation

Dried plant rhizomes (410 g) were incubated with distilled water at 40°C for 24 h, extracted with 96% ethanol for 25 h at room temperature, then ethanol was evaporated using a vacuum evaporator (40°C). Next, water was added to the residue and the whole was frozen and lyophilised yielding 80.1 g of extract. Obtained sample was defatted by petroleum ether yielding 78.2 g of degreased material. n-Butanol/water extraction was performed for part of this material (71 g). Each 10 g of lyophilisate were mixed with 250 ml of distilled water and extracted with 80 ml of n-butanol three times. Butanol layers were collected and n-butanol was removed at low pressure using a rotatory evaporator at 35°C. The extract was placed in water, frozen, and lyophilised giving 7.5 g of material. A solution of the extract (40 ml) in a mixture of CHCl₃/CH₃OH/H₂O (72 v: 18 v:1.8 v) was transferred to the silica gel Kieselgel 60 column and separated into fractions by gradient flash chromatography. Elution was conducted with a mixture of CHCl₃/CH₃OH/H₂O with gradually increasing volumes of methanol (72v: 18v: 1.8v; 63v: 27v: 2v; 54v: 36v: 2.5v; 45v: 45V: 3v; 27v: 63v: 4v; 0v: 100v: 0v respectively) with the flow rate of the mobile phase 15-18 ml/min.

The presence of saponins in the eluents was monitored by TLC on precoated Kieselgel 60 plates developed with CHCl₃/MeOH/H₂O (7v/3v/0.5v). The chromatograms were visualised with Liebermann-Burchard reagent (Ac₂O/CHCl₃/H₂SO₄ at 20v/50v/1v) and heated at 90°C for 10 min.

Single eluents of 10 ml from the column chromatography of similar composition were combined, which resulted in 11 sub-fractions. Organic solvents were removed at low pressure in a rotatory evaporator at 35°C. Distilled water was added to each sub-fraction and the aqueous suspensions obtained were frozen and freeze-dried, which yielded the following: 7-25-954.3 mg, 26-71-1934.1 mg, 72-85-247 mg, 86-92-129.7 mg, 93-103-415.8 mg, 104-109-149.1 mg, 110-117-86.5 mg, 118-136-15.2 mg, 137-159-100.5 mg, 160-186-288.3 mg, 187-198-96.8 mg. The saponins from each fraction were isolated by isocratic reversed-phase high-performance liquid chromatography (RP HPLC) using mobile phase MeOH/CH₃CN/H₂O 32v: 25v: 25v and flow rate 3.8 ml/min. The mobile phase was removed (low pressure evaporation at 40°C), then the saponins were suspended in water, frozen and lyophilised. No pennogenyl saponins were found in the last four sub-fractions. MALDI TOF and NMR spectra of all saponins were recorded [Figures A.1. and B.1. Appendix].

Figure A.1.

Maldi toff ms spectra of the saponins isolated from rhizomes of Paris quadrifolia L.: a)-1, b)-2, c)-3, d)-4, e)-5, f)-6

Figure B.1.

1H NMR spectra of the saponins isolated from rhizomes of Paris quadrifolia L.: a)-1, b)-2, c)-3, d)-4, e)-5, f)-6

Pennogenin 3-O-β-D-glucopyranoside (1): White powder; MALDI TOF MS m/z: 593 [M + 1]⁺, 575 [M + 1-18]⁺, 615 [M + 23]⁺, 631 [M + 39]⁺, molecular formula C₃₃H₅₂O₉.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (2): White powder; MALDI TOF MS m/z: 739 [M + 1]⁺, 721 [M + 1-18]⁺, 761 [M + 23]⁺, 777 [M + 39]⁺, molecular formula C₃₉H₆₂O₁₃.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1 →2)-β-D-glucopyranoside (3): White powder; MALDI TOF MS m/z: 739 [M + 1]⁺, 721 [M + 1-18]⁺, 761 [M + 23]⁺, 777 [M + 39]⁺, molecular formula C₃₉H₆₂O₁₃.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (4): White powder; MALDI TOF MS m/z: 885 [M + 1]⁺, 867 [M + 1-18]⁺, 907 [M + 23]⁺, 923 [M + 39]⁺, molecular formula C₄₅H₇₂O₁₇.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (5): White powder; MALDI TOF MS m/z: 885 [M + 1]⁺, 867 [M + 1-18]⁺, 907 [M + 23]⁺, 923 [M + 39]⁺, molecular formula C₄₅H₇₂O₁₇.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (6): White powder; MALDI TOF MS m/z: 1031 [M + 1]⁺, 1013 [M + 1-18]⁺, 1053 [M + 23]⁺, 1069 [M + 39]⁺, molecular formula C₅₁H₈₂O₂₁.

Cytotoxicity assay

Cell culture

The HL-60 human promyelocytic leukaemia cell line was cultured in RPMI 1640 medium supplemented with 10% foetal bovine serum, 2 mM glutamine, 100 units/ml penicillin and 100 μg/ml streptomycin. The HeLa human cervical adenocarcinoma and MCF-7 human breast cancer cell lines were cultured in Dulbecco's Modified Eagle's Medium (DMEM) supplemented with 10% foetal bovine serum, 2 mM glutamine, 100 units/ml penicillin and 100 μg/ml streptomycin. Cultures were maintained in an incubator in a humidified atmosphere with 5% of CO₂ at 37°C (Heraceus, Hera cell).

Evaluation of cytotoxicity

Cell viability was determined using the MTT ((3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.[35,36,37] Cells were seeded in 96-well plates at a density of 5 × 10³ cells/well and treated for 24 h with the isolated pennogenyl saponins in the concentration range 0-50 μg/ml. Next, MTT (0.5 mg/ml) was added directly to the medium and cells were further incubated for 3 h at 37°C. The optical density of the formazan solution was measured at 550 nm with a plate reader (Victor, 1420 multilabel counter). Results are expressed as IC₅₀ values. ± SD was calculated from at least three independent experiments.

RESULTS AND DISCUSSION

The isolation of pennogenyl saponins from P. quadrifolia rhizomes was completed in a few steps described in the experimental part. The procedure involved drying, ethanol extraction, degreasing and n-butanol/water extraction. The n-Bu-OH soluble fraction was subjected to column chromatography on silica gel in the eluent mixture ingredients gradient mode concentration (with growing concentration of MeOH). Eluates were monitored by TLC and 11 sub-fractions were obtained. Six pennogenyl saponins 1-6 (0.002, 0.019, 0.005, 0.194, 0.017 and 0.158% of the rhizome dry mass respectively) were isolated from 1-7 sub-fractions by semi-preparative isocratic RP HPLC. An especially large amount of saponin 6 was found in three sub-fractions: 93-103 (74.17%), 104-109 (62.42%) and 86-92 (61.27%) [Table 2].

Table 2.

Contents of pennogenyl saponins in P. quadrifolia L. fractions

Structural studies

The structures of pennogenyl saponins 1-6 [Figure 1] were elucidated by analyses of their molecular mass (MALDI TOF MS) and 1D and 2D NMR spectra (¹H, COSY, TOCSY, ROESY, HMQC, HMBC).

Figure 1.

The structures of the saponins isolated from rhizomes of P. quadrifolia L.

The following cationised ions of the saponins under study were observed in the MALDI TOF MS spectra: [M + H]⁺ (quasimolecular), [M + Na]⁺, [M + K]⁺ and [M + H-H₂O]⁺, which are consistent with their molecular formulae and molecular weights for the following compounds: 1-C₃₃H₅₂O₉, 592 Da, 2-C₃₉H₆₂O₁₃, 738 Da, 3-C₃₉H₆₂O₁₃, 738 Da, 4-C₄₅H₇₂O₁₇, 884 Da, 5-C₄₅H₇₂O₁₇, 884 Da, 6-C₅₁H₈₂O₂₁, 1030 Da [Figure 1 and Figure A.1-Appendix].

All ¹H and ¹³C chemical shifts of compounds 1-6 were assigned using ¹H, DQF-COSY, TOCSY, and HMQC experiments [Table 1]. Detailed analysis of the ¹H and ¹³C NMR data of all the isolated compounds [Table 1] enabled the saponins to be identified: they consisted of a pennogenin residue as an aglycone part and sugar moieties.[4,30,31,38] Since our elucidations of all the aglycone parts were in very good agreement with the literature data, only the analysis of the sugar part of the saponins is described in detail here. The constituent monosaccharides of all six saponins possessed six-membered rings: They were assigned by the lack of carbon atom signals in the δ ~83-88 region of the ¹³C NMR spectrum [Table 1].[39,40]

Table 1.

¹H and ¹³C NMR data of compounds 1.6 (700 MHz, C₆D₅N)

L configurations of all rhamnose residues and D configuration of glucose were identified by GLC of their (S)-(+)- and (±)-2-butyl glycosides.

Pennogenin 3-O-β-D-glucopyranoside (1): Examination of the ¹H NMR spectrum [Figure B.1.A- Appendix] revealed the presence of only one anomeric proton signal at δ 5.041, which was identified on the basis of the HMQC cross peak at δ 5.041/102.68. The gluco configuration of this residue was assigned on the basis of the ³J_{H, H} coupling constant pattern. Moreover, ³J_{H-1, H-2} = 8.2 Hz clearly revealed a β-configured Glc residue. The HMBC experiment (not shown) identified the linkage between Glc and pennogenin residues as 1→3. Strong cross-peaks H-1 of Glc/C-3 of pennogenin (δ 5.041/78.19), as well as of H-3 of pennogenin/C-1 of Glc (δ 3.919/102.68) were observed in the spectrum.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (2): The ¹H NMR spectrum of compound 2 [Figure B.1.B-Appendix] was very similar to one described above. The spectrum contained two anomeric proton signals at δ 4.947 and 5.911. The first residue was identified as β-Glc (³J_{H-1, H-2} = 8.1 Hz) substituted at C-4 (δ 78.45), and the second one as terminal α-Rha (I). The α configuration of the rhamnopyranosyl unit (³J_{H1, H2} < = 1.5Hz) was deduced from the absence of strong intraresidual ROESY correlations between protons H-1 and H-3/H-5. This was also confirmed by ¹J_{H1, C1} = 169 Hz, measured from the residual direct correlation observed in the HMBC spectrum, which is in agreement with that reported for the alpha anomer of rhamnopyranose.[41] The HMBC experiment confirmed the 1→3 linkage of Glc to pennogenin (H-1 of Glc/C-3 of pennogenin at δ 4.947/78.28, and H-3 of pennogenin/C-1 of Glc at δ 3.863/102.64). Furthermore, the substitution of Glc by the Rha (I) residue at C-4 (H-1 of Rha (I)/C-4 of Glc at δ 5.911/78.45, and H-4 of Glc/C-1 of Rha (I) at δ 4.485/102.81) was demonstrated.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (3): The ¹H NMR spectrum of compound 3 [Figure B.1.C- Appendix] also showed two anomeric proton signals (δ 5.059, and 6.412). The first one belonged to β-Glc (³J_{H-1, H-2} = 7.3 Hz) substituted at C-2 (δ 78.43), and the second to a terminal α-Rha (II) (¹J_{H1, C1} = 171 Hz). The HMBC spectrum revealed the 1→3 linkage of Glc to pennogenin (H-1 of Glc/C-3 of pennogenin at δ 5.059/78.60, and H-3 of pennogenin/C-1 of Glc at δ 3.946/100.97), as well as the substitution of Glc by the Rha (II) residue at C-2 (H-1 of Rha (II)/C-2 of Glc at δ 6.412/78.43, and H-2 of Glc/C-1 of Rha (II) at δ 4.297/102.69).

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranoside (4): Three anomeric signals were identified in the anomeric region of the ¹H NMR spectrum of compound 4 [Figure B.1.D - Appendix]. The signal with the lowest chemical shift (δ 4.949) was identified as H-1 of β-Glc (³J_{H-1, H-2} = 7.7Hz) substituted at C-4 (δ 77.79), then the signal at δ 5.890 belonging to α-Rha (I) (¹J_{H1, C1} = 170Hz) substituted at C-4 (δ 80.53), and finally the signal at δ 6.336 represented the terminal α-Rha (III) (¹J_{H1, C1} = 171Hz). In the HMBC spectrum, the cross-peaks at δ 4.949/78.37 (H-1 of Glc/C-3 of pennogenin) and at δ 3.854/102.64 (H-3 of pennogenin/C-1 of Glc) indicated glycosylation of the aglycone at the C-3 position. Another cross-peak between the second anomeric proton at δ 5.890 and the carbon at δ 77.79 (H-1 of Rha (I)/C-4 of Glc), and the cross-peak at δ 4.483/102.32 (H-4 of Glc/C-1 of Rha (I)) revealed the 1→4 linkage of Rha (I) to Glc. Finally, the cross-peak between the third anomeric proton at δ 6.336 and the carbon at δ 80.53 (H-1 of Rha (III)/C-4 of Rha (I)), and the cross-peak at δ 4.483/103.33 (H-4 of Rha (I)/C-1 of Rha (III)) revealed the 1→4 linkage of Rha (III) to Rha (I).

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (5): The ¹H NMR spectrum of compound 5 [Figure B.1.E - Appendix] also showed three anomeric proton signals (δ 4.944, 5.872, and 6.415). The first one belonged to β-Glc (³J_{H-1, H-2} = 6.9 Hz) substituted at C-2 (δ 77.98) and C-4 (δ 78.76), as well as two other signals of two terminal α-Rha residues (¹J_{H1, C1} = 169 Hz, and ¹J_{H1, C1} = 171 Hz respectively). The HMBC spectrum confirmed the 1→3 linkage of Glc to pennogenin (H-1 of Glc/C-3 of pennogenin at δ 4.944/78.06, and H-3 of pennogenin/C-1 of Glc at δ 3.861/100.31). Moreover, the cross-peaks at δ 5.872/78.76 (H-1 of Rha (I)/C-4 of Glc) and at δ 4.399/103.36 (H-4 of Glc/C-1 of Rha (I)) revealed the linkage 1→4 between Rha (I) and Glc, and the cross-peaks at δ 6.415/77.98 (H-1 of Rha (II)/C-2 of Glc) and at δ 4.399/102.25 (H-2 of Glc/C-1 of Rha (II)) revealed the linkage 1→2 between Rha (II) and Glc.

Pennogenin 3-O-α-L-rhamnopyranosyl-(1→4)-α-L-rhamnopyranosyl-(1 →4)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranoside (6): Four anomeric signals were identified in the anomeric region of the ¹H NMR spectrum of compound 6 [Figure B.1.F - Appendix]. The signal with the lowest chemical shift (δ 4.946) was identified as H-1 of β-Glc (³J_{H-1, H-2} = 7.0 Hz) substituted at C-2 (δ 77.95) and at C-4 (δ 77.82), then the signal at δ 5.848 belonging to α-Rha (¹J_{H1, C1} = 169 Hz) substituted at C-4 (δ 80.59), and finally two signals at δ 6.297 and 6.413 representing terminal α-Rha residues (¹J_{H1, C1} = 171 Hz, and ¹JH1, C1 = 172 respectively).

In the HMBC spectrum, the cross-peaks at δ 4.946/78.21 (H-1 of Glc/C-3 of pennogenin) and at δ 3.858/100.38 (H-3 of pennogenin/C-1 of Glc) indicated glycosylation of the aglycone at C-3. Another cross-peak at δ 5.848/77.82 (H-1 of Rha (I)/C-4 of Glc) and the cross-peak at δ 4.418/102.28 (H-4 of Glc/C-1 of Rha (I)) revealed the 1→4 linkage of Rha (I) to Glc. Finally, the position of glycosylation by the two remaining terminal Rha residues was identified. The cross-peak at δ 6.297/80.59 (H-1 of Rha (III)/C-4 of Rha (I)) and the cross-peak at δ 4.457/103.28 (H-4 of Rha (I)/C-1 of Rha (III)) revealed the 1→4 linkage of Rha (III) to Rha (I), while the cross-peak at δ 6.413/77.95 (H-1 of Rha (II)/C-2 of Glc) and the cross-peak at δ 4.226/102.15 (H-2 of Glc/C-1 of Rha (II)) revealed the 1→2 linkage of Rha (II) to Glc.

Bioassay studies

The isolated eleven sub-fractions were evaluated for their cytotoxic activity against HL-60 and HeLa cells. The seven sub-fractions (7-25, 26-71, 72-85, 86-92, 93-103, 104-109, 110-117) showed cytotoxicity below 100 μg/ml [Table 3]. The fractions 86-92, 93-103, 104-109 with large amount of compound 6 [Table 2] were the most potent [Table 3].

Table 3.

Cytotoxic activity of sub-fractions from P. quadrifolia L. extract

The six compounds isolated from the all sub-fractions were tested on HL-60, HeLa and MCF-7 cells. Pennogenyl saponins 5 and 6 exhibited cytotoxic activity against HL-60, HeLa and MCF-7 tumour cells with IC₅₀ values of 1.0 ± 0.04 μg/ml, 1.8 ± 0.072 μg/ml and 2.4 ± 0.096 μg/ml respectively, and 2.0 ± 0.08 μg/ml, 2.5 ± 0.125 μg/ml and 3.2 ± 0.128 μg/ml respectively. Saponins 1, 2 and 4 or without the ramnosyl residue or without the terminal ramnosyl residue linked to C-2 of the glucosyl group did not show any cytotoxic activity [Table 4].

Table 4.

Cytotoxic activity of pennogenyl saponins from P. quadrifolia L. rhizomes

CONCLUSION

The six saponins studied in this paper have been isolated at the same time from rhizomes of one species of Paris and fully structurally characterised using spectroscopic and chemical methods. The spirostan saponins 1, 2, 3 and 4 were obtained from P. quadrifolia rhizomes for the first time. The isolation and the identification of six pennogenyl saponins from P. quadrifolia rhizomes constitute significant contribution into the general knowledge of chemical composition of the Paris family, particularly in the field of saponin substances and P. quadrifolia L. itself.