Year : 2009 | Volume
: 5 | Issue : 17 | Page : 28--36
Chemical Composition and Hepato-protective activity of Imperata cylindrica Beauv
Gamal A Mohamed1, Ahmed Abdel-Lateff2, Mostafa A Fouad2, Sabrin R.M Ibrahim3, Ehab S Elkhayat1, Tatsufumi Okino4,
1 Department of Pharmacognosy, Faculty of Pharmacy, Al-Azhar University, Assiut 71524, Egypt
2 Department of Pharmacognosy, Faculty of Pharmacy, Minia University, 61519 Minia, Egypt
3 Department of Pharmacognosy, Faculty of Pharmacy, Assiut University, Assiut 71526, Egypt
4 Faculty of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan
Ehab S Elkhayat
Department of Pharmacognosy, Faculty of Pharmacy, Al-Azhar University, Assiut 71524
Phytochemical study of the aerial parts of Imperata cylindrica Beauv. (Graminae), growing in Egypt afforded four methoxylated flavonoids 1-4 , β-sitosterol-3-0-β-D-glucopyranosyl-6 «SQ» -tetradecanoate 5 , 3-hydroxy-4-methoxybenzaldehyde 6 , together with daucosterol, β-sitosterol and α-amyrin 7-9. To the best of our knowledge, this is the first isolation of compounds 1-5 from the genus Imperata. A significant hepato-protective activity had been observed upon co-administration of the methanolic extracts of I. cylindrica with CCl 4 . The structures were determined using spectroscopic data; 1D ( 1 H and 13 C), 2D (HSQC, and HMBC) NMR; MS; UV and IR.
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Mohamed GA, Abdel-Lateff A, Fouad MA, Ibrahim SR, Elkhayat ES, Okino T. Chemical Composition and Hepato-protective activity of Imperata cylindrica Beauv.Phcog Mag 2009;5:28-36
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Mohamed GA, Abdel-Lateff A, Fouad MA, Ibrahim SR, Elkhayat ES, Okino T. Chemical Composition and Hepato-protective activity of Imperata cylindrica Beauv. Phcog Mag [serial online] 2009 [cited 2021 Apr 23 ];5:28-36
Available from: http://www.phcog.com/text.asp?2009/5/17/28/57982
Imperata cylindrica Beauv. is widely distributed in tropical regions. The Korean folk medicine has described the rhizomes as diuretic, anti-inflammatory, and antipyretic  . Previous phytochemical studies of the rhizomes of I. cylindrica have resulted in the isolation of neuro-protective chromones  , several arborane compounds such as arundoin, cylindrin and fernenol  , in addition to cylindol  , cylindrene  , graminones  and imperarene  .
This study is a phytochemical and biological evaluation of I. cylindrica Beauv. growing in Egypt, we describe the isolation and structural elucidation of several compounds: four methoxylated flavonoids 1-4, tetradecanoyl ester of sitosterol glucoside 5, and an aldehyde 6. These compounds are reported for the first time from genus Imperata. In addition to daucosterol, B-sitostrol and a-amyrin. More over, the total methanolic extract showed potent hepatoprotective activity and the compounds 1-5 showed cytotoxic activity elicited by the brine shrimp lethality assay.
Materials and Methods
The fresh aerial parts of I. cylindrica Beauv. were collected in September 2006 from the wild plants around the campus of Al-Azhar University, Assiut, Egypt. The plant material was kindly identified by Prof. Dr. A. Fayed, Professor of Plant Taxonomy, Faculty of Science, Assiut University, Egypt. A voucher specimen was deposited in the Department of Pharmacognosy herbarium, Faculty of Pharmacy, AlAzhar University, Assiut (Registration code WAz-006 IM).
Pre-coated silica gel 60 F 254 plates (Merck) were used for TLC. Vacuum liquid chromatography (VLC) was carried out using silica gel 60, 0.04-0.063 mm mesh size (Merck). The solvent systems used for TLC analyses were n-hexane-EtOAc (95:5, solvent system I), CHCl 3 -Me0H (90:10, solvent system II) and CHCl3-Me0H (85:15, solvent system III). The TLC plates were visualized by UV light at λmax 255 and 366 nm followed by spraying with p-anisaldehyde/H 2 SO 4 reagent and heating at 110°C for 1-2 min. HPLC was performed on semi-preparative RP-18 column (Cosmosil 5C18 ARII, 250 x 10 mm) with a UV detector at λmax 220 nm and flow rate of 2.5 ml/min. Melting points were carried out in electrothermal 9100 Digital Melting Point (England). UV spectra were recorded on a Hitachi 300 spectrometer. 1 H and 13 C-NMR spectra were recorded on a JEOL-JNM-EX-400 spectrometer (400 MHz for 1H and 100 MHz for 13 C, respectively). El-MS data were obtained with a JEOL JMS-700T mass spectrometer. All solvents were distilled prior to use. NMR grade solvents (Merck), were used for NMR analysis.
Extraction and Isolation
The air-dried powdered aerial parts of I. cylindrica (1.2 kg) were extracted with 70 % MeOH (6 x 5 L) at room temperature; evaporation of the methanol extract under reduced pressure affords a dark brown residue (34.1 g). The residue was suspended in 500 ml water and was successively partitioned with n-hexane, CHCl3 and ethyl acetate to yield residues of 4.15, 8.74 and 8.4 g respectively, and an aqueous residue of 12.3 g. Preliminary cytotoxicity assay on the crude fractions showed that the n-hexane and ethyl acetate fractions possess cytotoxic activity as elicited by brine shrimp assay. The ethyl acetate residue (8.4 g) was subjected to VLC on silica gel using CHCl 3 : MeOH gradients and afforded 8 fractions. Fraction 4 (225 mg) was chromatographed on silica gel and eluted with EtOAc: MeOH gradient followed by final purification on semi-preparative RP-18 HPLC column using 25% MeCN in H2O to afford compounds 1 (20.2 mg) and 2 (13.7 mg). Meanwhile, fraction 5 (238 mg) was chromatographed on silica gel and eluted with EtOAc: MeOH gradient, followed by semi-preparative RP-18 HPLC [MeOH: H2O (40:60)], to afford 3 (8.3 mg) and 4 (6.5 mg). On the other hand, the n-hexane fraction was subjected to VLC on silica gel column eluted with n-hexane:Et0Ac gradient to yield 7 fractions. Fractions 4 (112 mg), 5 (188 mg), 6 (224 mg), and 7 (118 mg) were separately chromatographed on silica gel eluted with CH2Cl2: EtOAc gradient to afford compounds 5 (38.2 mg), 6 (7.3 mg), 7 (12.4 mg), 8 (15.9 mg) and 9 (21.0 mg), respectively.
Alkaline treatment of compound 5 (8)
Alkaline treatment of compound 5 described by Nakano et al, afforded sitosteryl-B-glucopyranoside (5a) and a methyl ester of fatty acid which was identified as tetradecanoic acid methyl ester by El-MS analysis. Aliquot of 5a was subjected to acid hydrolysis to afford D-glucose that was identified by comparison with authentic sugar samples [TLC paper-chromatography using n-butanol: acetic acid: water (4:1:5)], in addition to B-sitosteryl moiety by direct comparison with authentic sample (IR, TLC and mixed melting point).
Tricin 1 . Yellow crystals (20.2 mg); R f = 0.62 (solvent system II); HRESI-MS (Neg. mode) m/z 329.0661 [M+ - H] - , calculated for C 17 H 13 0 7 . UV λmax (MeOH): 270, 352; +NaOMe 279, 413; +AlCl 3 276, 368 sh, 394; +AlCl 3 /HCl 277, 389; +NaOAc 268, 411.
Jaceidin 2 : Yellow sticky residue (13.7 mg); R f = 0.71 (solvent system II); HRESI-MS (Neg. mode) m/z 359.0767 [M + - H] - , calculated for C 18 H 15 0 8 . UV λmax nm (MeOH): 272, 354; +NaOMe 274, 412; +AlCl 3 285 sh, 391; +AlCl 3 /HCl 283 sh, 390; +NaOAc 274, 330 sh, 362.
Quercetagetin-3,5,6,3.'-tetramethyl ether 3 : Yellow amorphous powder (8.3 mg); R f = 0.79 (solvent system II); HRESI-MS (Neg. mode) m/z 373.0923 [M+- H]-, calculated for C19H1708. UV λmax nm (MeOH): 269, 345; +NaOMe 270, 405; +AlCl 3 269, 344; +AlCl3/HCl 269, 344; +NaOAc 275, 388.
3,5-Di-O-methyl-kaempferol 4 ,,,: Yellow amorphous powder (6.5 mg); R 1 = 0.65 (solvent system II); UV λmax nm (MeOH): 275, 339; +NaOMe 282, 391; +AlCl 3 275, 341; +AlCl 3 /HCl 276, 340; +NaOAc 290, 372; HRESI-MS (Neg. mode) m/z 313.0712 [M + - H] - , calculated for C 17 E 13 0 6
β-Sitosterol-3-0-β-D-glucopyranosy1-6"- tetradecanoate 5 : White greasy substance (38.2 mg); R f = 0.78 (solvent system III); HRESI-MS (Neg. mode) m/z 785.6295 calculated for C49H8507.
3-Hydroxy-4-methoxy benzaldehyde 6 : White needles (7.3 mg); R f = 0.52 (solvent system II); mp 117-118°C; HR ESI-MS, mlz 152 (M + , 100%). HRESI-MS (Neg. mode) mlz 151.0395 [M+ - H], caculated for C8H703.
Brine shrimp lethality test
The test was performed using 5 and 10 pg of the obtained fractions and isolated compounds as published by Mayer and Edrada et al. ,. The test was done in triplicate.
1.Experimental animals : Adult male albino rats of Charles River strain weighing 120-150g were obtained from Assiut University animal house.
2.CCl 4-induced hepatotoxicity : The animals were divided into four groups of six animals each.
Group I: Normal control received distilled water (1 ml/kg) daily for 5 days and olive oil (1 ml/kg, intraperitoneal) on days 2 and 3.
Group II: CCl 4 control received distilled water (1 ml/kg) daily for 5 days and CCl 4 : olive oil (1:1, 1ml/kg, intraperitoneal) on days 2 and 3.
Group III: Treated with I. cylindrica extract orally through intragastric feeding tube at dose of 100 mg/kg, the extract dose was fixed after trying out different doses (25, 50, 100 and 150 mg/kg).
Groups IV: Treated with I. cylindrica extract doses of 100 mg/kg, for 5 days and 30 mins after administration of extract the rats received CCl 4 : olive oil (1:1, lml/kg, intraperitoneal) on days 2 and 3.
3. Biochemical estimations : The rats were sacrificed on the sixth day and blood was collected from orbital sinus in plain tubes. The serum was obtained by centrifugation and serum samples were taken for biochemical assays; namely glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) .
Results and Discussion
Compound 1 .
The HR ESI-MS identified a molecular formula of C 17 H 14 0 7 . 1 H NMR spectrum showed the presence of two methoxyl groups as a singlet peak at δH 3.91 (6H, s). A singlet proton at δH 6.96 (1H, s) which showed HSQC correlation to the carbon at do 103.5 indicated a flavone structure  . Two doublet signals at δH 6.21 (1H, d, J = 1.7 Hz, H-6) and 6.55 (1H, d, J = 1.7 Hz, H8) revealed meta-disubstituted ring A as confirmed by the carbon resonances at δc 98.7 and 94.0, respectively. Furthermore, a singlet signal at δH 7.31 (2H, s, H-2', 6') revealed trisubstituted ring B which was confirmed by the carbon resonances at δc 104.2, 147.9 and 139.6 , . The downfield proton at δH 12.95 afforded the presence of a hydrogen bonded hydroxyl group at C-5 and confirmed by the carbon atom resonated at δc 161.0. The HMBC experiment afforded the attachment of two methoxyl groups at C3' and C-5', which identified a tricin structure  . It is the first isolation of this compound from the genus lmperata.
Compound 2 .
The HR ESI-MS identified a molecular formula of C 1$ H 16 0 8 . The 1 H NMR spectrum, showed resonances for three methoxyl groups at δH 3.92, 3.87, and 3.78 which were correlated to the carbons resonated at δc 54.3, 58.3 and 58.7, respectively as shown by the HSQC experiment. More over, three proton signals at δH 6.91 (1H, d, J = 8.3 Hz), 7.61 (1H, dd, J = 8.3, 1.7 Hz) and 7.69 (1H, d, J = 1.7 Hz) were assigned to H-5', H-6' and H-2', respectively. On comparison to 1, absence of the singlet proton signal at δH 6.96 and its carbon at δc 103.5, suggested a flavonol structure , . The HMBC experiment afforded the attachment of the methoxyl groups at C-3', 3 and 6[Figure 1], [Figure 2]. The compound was identified as jaceidin  , which was isolated for the first time from the genus Imperata.
Compound 3 .
The HR ESI-MS spectrum revealed a molecular formula of C 19 H 18 0 8 . The 1 H and 13 C NMR spectral data of 3 [Table 1], [Table 2] and [Table 3] afforded a similar structure to 2 except in presence of additional singlet proton signal at δH 3.35 assigned to another methoxyl group. This was confirmed by the carbon resonance at δc 61.5. The HMBC experiment afforded the attachment of the additional methoxyl group at C-5 [Figure 2]. Accordingly, compound 3 was identified as quercetagetin-3,5,6,3'-tetramethyl ether  , it is isolated for the first time from the genus lmperata.
Compound 4 .
HR ESI-MS revealed a molecular formula of C17H1406. The 1 H and 13 C-NMR indicated a similar structure to 2 . The 1 H and 13 C -NMR spectra of 4 [Table 1] and [Table 2], showed the presence of a meta-disubstituted ring A and para-disubstituted ring-B. The HMBC experiment afforded the attachment of the methoxyl groups at 6H 3.4 and 3.96 (3H, s), to C-3 and C-5, respectively [Figure 2]. Compound 4 was identified as 3, 5-di-0methyl-kaempferol ,,,,, it is isolated for the first time from the genus lmperata.
Compound 5 .
The HRESI-MS spectrum identified a molecular formula of C 49 H 86 0 7 . 1 H NMR (400 MHz, C 5 D 5 N): showed the presence of a triplet methyl group at δH 1.1 (3H, t), in addition to six methyl groups at δH 0.66 (3H,~) , 0.91 (3H,~), 0.97 (3H,d, J = 6.4 Hz ), 0.89 (3H,d, J = 6.4 Hz), 0.93 (3H,d, J = 6.5 Hz ) and 0.87 (3H, t). More over, a β-anomeric sugar proton at δH 457(1H, d, J = 7.2 Hz), indicated a gluco-steroidal structure. 1 H and 13 C-NMR spectral data of 5 indicated signals for sitosteryl  and glucopyranosyl moieties  in addition to an ester carbonyl carbon at δc 174.1, a methyl group at δC 14.1 in addition to a cluster of methylene groups at do 22.7-34.3. The downfield shift of C-6' (63.7) and an upfield shift of C-5' (73.8) in the 13 C-NMR spectrum revealed the attachment of the fatty acid at C-6' of the glucose moiety  that was confirmed by the HMBC experiment. Alkaline treatment of compound 5 afforded sitosteryl-Dglucopyranoside and tetradecanoic acid methyl ester that was identified by [I-MS analysis. Acid hydrolysis revealed the presence of D-glucose and sitosterol. Accordingly, compound 5 was identified as β-sitosterol-3-0-β-D-Blucopyranosyl-6 ' -tetradecanoate
, it is isolated for the first time from the genus lmperata. Compounds ( ,,, ) were identified as 3-hydroxy-4- methoxy-benzaldehyde , daucosterol ,, β-sitoststerol  and a-amyrin , respectively on comparing their physical and spectral data with literatures. These compounds were isolated for the first time from I. cylindrical.
All the isolated compounds were evaluated for their cytoxic activity using brine shrimp assay [Table 4]. Compounds 2, 3 and 5 showed strong activity while compounds 1 and 4 showed moderate activity.
Liver injury in rats was induced through intraperitoneal administration of CCI 4 that was manifested by significant elevation in the level of serum hepatic marker enzymes; namely glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) as shown in [Table 5]. The activities of the GOT and GPT enzymes in the serum of control and experimental groups showed marked elevation (p 4 administered rats) when compared with group 1 (Control rats). Activities of these enzymes in serum were maintained at near normal levels (p cylindrica and CCI 4 co-administrated group). Group 3, rats treated with I. cylindrica extract alone, show minor changes when compared with group 1 (control rats), which revealed the non toxic effect of the I. cylindrica extract.
The authors are grateful to Professor A. Fayed (Plant Taxonomy Department, Faculty of Science Assuit University, Egypt) for the identification of the plant material and Mr. Hiroshi Matsuura, Faculty of Graduate School of Environmental Science, Hokkaido University, for his help in measuring the NMR and mass spectra. This work is a part of the DAAD project (Code 134.104401. 212).
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