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Chemical composition, antioxidant and anticholinesterase potentials of essential oil of Rumex hastatus D. Don collected from the North West of Pakistan
© Ahmad et al. 2016
Received: 1 October 2015
Accepted: 12 January 2016
Published: 25 January 2016
Ethnomedicinally Rumex hastatus D. Don has been used since long for various ailments especially in neurological disorders. The reported data and the importance of Rumex genus demonstrate the vital medicinal value of R. hastatus.
In the current investigational study, isolation of essential oil and its antioxidant and anticholinesterase assays were performed. The essential oil of R. hastatus was analyzed by GC-MS for the first time. The essential oil was evaluated for anticholinesterase and antioxidant assays. The anticholinesterase assay was conducted at various concentrations (62.5 to 1000 μg/ml) against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Similarly, the antioxidant potential was determined using DPPH and ABTS free radicals.
The GC-MS analysis of essential oil showed 123 components. The result recorded for the anticholinesterase assays demonstrated a marked potential against AChE and BChE with IC50 values of 32.54 and 97.38 μg/ml respectively which were comparable with the positive control i.e., galanthamine (AChE, IC50 = 4.73 μg/ml and BChE, IC50 = 11.09 μg/ml). The antioxidant assays against DPPH and ABTS free radicals also exhibited significant scavenging potential with IC50 values of 3.71 and 6.29 μg/ml respectively, while for ascorbic acid the IC50 value was <0.1 μg/ml against both free radicals.
Based on the current investigational studies, it may be concluded that R. hastatus is an effective source of essential oil's components having anticholinesterase and antioxidant potentials, which after subjecting to drug development may lead to novel drug candidates against neurodegenerative disorders.
KeywordsEssential oil Acetylcholinesterase Butyrylcholinesterase Antioxidant GC-MS Free radicals Rumex hastatus
A brief history of medicine demonstrates the use of herbal medicine for the effective treatment of various ailments. Herbal medicine has been used since long in various forms including the decoction, powdered sample, oleoresins, crude extracts, fixed oil, essential oil etc . Various plants have been used in multiple types of food items for preservation and therapeutic effects . In this regards, essential oils have been manifested by several reporters to play a major role. Essential oils have the property to attenuate the effects of free radicals, e.g, reactive oxygen species (ROS) which are derived from metabolism of oxygen and exogenous agents . ROS are responsible for wide variety of diseased conditions including oxidative stress and nervous disorders . Essential oils are well-known for their radicals scavenging properties and amelioration of various cognitive disorders. Among the cognitive disorders, Alzheimer’s disease (AD) is the most common in elderly people . One of the best therapeutic approaches for AD is to increase the concentration of the neurotransmitter (Acetylcholine) by inhibiting the enzyme (acetylcholinesterase) responsible for its breakdown. Various drugs originated either from natural or synthetic sources are being used for the management of AD and other nervous disorders . Similarly, it has also been reported that oxidative stress are responsible for wide variety of mental diseases due to neuronal degeneration and other factors. Oxidative stress is mainly developed due to increase in concentration of free radicals within the body. The free radicals have been reported by numerous researchers to possess multiple destructive properties, due to which interest has been focused to scavenge the free radicals somehow and avoid their deteriorating effects . In this context, investigators are trying to explore more and more sources of natural and synthetic bioactive principles . The natural drugs are being preferred over the synthetic due to their negligible harmful and deleterious effects . That’s why researchers are trying to explore novel sources of natural medicine [10–18]. Among the natural sources, herbal medicines have been shown promising results due to the presence of numerous secondary metabolites and essential oils. Essential oils isolated from various plants have been reported to possess marked acetylcholinesterase inhibitory and radicals scavenging potential [19–21]. Traditional knowledge also demonstrates the use of essential oils for various nervous system disorders .
R. hastatus D. Don belongs to the family Polygonaceae. Various members of this family have been reported to be used against paralysis, headache and other nervous system disorders [23–26]. Various solvent samples of R. hastatus have recently been reported to possess strong anticholinesterase and antioxidant potentials . To date, the chemical composition of essential oil of R. hastatus has not been reported or evaluated for any pharmacological activity. Based on the literature survey and medicinal importance of R. hastatus, the current investigational study is arranged to isolate the essential oil, analyze the chemical composition and to evaluate for the anticholinesterase and antioxidant potentials, which may be a possible remedy for oxidative stress and nervous system disorder.
Plant sample collection
The aerial parts of R. hastatus were collected from the proximity of University of Malakand. The plant was identified by plant taxonomist Ali Hazrat and deposited with voucher number (1015SJ) in the herbarium of Department of Botany, Shaheed Benazir Bhutto University Sheringal, Dir (U), KPK, Pakistan. Extraction of essential oil of R. hastatus was performed by hydrodistillation using clevenger type apparatus . The essential oil obtained was stored at -20 °C until required.
Chemicals and drugs
DPPH (Sigma Aldrich CHEMIE GmbH USA, code 101341986), K2S2O4 (Riedel-de Haen Germany), ABTS (Sigma Aldrich USA, code 1001551916), Gallic acid (GmbH USA), Folin Ciocalteu reagent (Merck Co. Germany). AChE (Electric eel type-VI-S, Sigma-Aldrich GmbH USA, code 1001596210), BChE (Equine serum Lyophilized Sigma-Aldrich GmbH USA, code 101292670), Acetylthiocholine iodide (Sigma-Aldrich UK, code 101303874), Butyrylthiocholine Iodide (Sigma-Aldrich Switzerland, code 101334643), DTNB (Sigma-Aldrich Germany, code 101261619), Galanthamine hydrobromide Lycoris Sp. (Sigma-Aldrich France, code G1660). K2HPO4, KH2PO4, KOH. All the chemical used were of analytical grade.
Gas Chromatography (GC) analysis
The GC analysis of essential oil was carried out via gas chromatograph Agilent USB-393752 (Agilent Technologies, Palo Alto, CA, USA) with HHP-5MS 5 % phenylmethyl siloxane capillary column (30 m × 0.25 mm × 0.25 μm film thickness; Restek, Bellefonte, PA) connected with FID detector. The oven was set at temperature of 70 °C for one minute and then increased to 180 °C at the rate of 6 °C/min for 5 min and lastly to 280 °C at the rate of 5 °C/min for 20 min. The temperature of injector and detector were maintained at 220 °C and 290 °C correspondingly. The flow rate of carrier gas i.e., Helium was 1 ml/min and the diluted samples (1/1000 in n-pentane, v/v) of 1 μl were manually injected in the split-less mode.
Gas Chromatography–Mass Spectrometry (GC-MS) analysis
The GC/MS of the essential oil was performed via USB-393752 gas chromatograph (Agilent Technologies, Palo Alto, CA, USA) with a HHP-5MS 5 % phenylmethyl siloxane capillary column (30 m × 0.25 mm × 0.25 μm film thickness; Restek, Bellefonte, PA) outfitted with an Agilent HP-5973 mass selective detector in the electron impact mode (Ionization energy: 70 eV) working under the experimental conditions as those maintained for GC.
Identification of components
The recognition of all the major constituents of oil was performed by comparing their retention times with the authentic compounds in the literature. Identification of compounds was further processed through the spectral data obtained from the Wiley and NIST libraries as well as fragmentation patterns’ comparisons of the mass spectra with data reported in literature or with those of mass spectra from literature [28, 29]. Each determination was processed in duplicate.
(Where V symbolizes the rate of reaction in the presence of inhibitor and Vmax stands for rate of reaction without inhibitor)
DPPH radical scavenging assay
ABTS radical scavenging assay
Estimation of IC50 values
The median inhibitory concentration i.e., IC50 values of AChE, BChE, DPPH and ABTS were determined by a linear regression analysis of the percent inhibition versus the concentrations of test samples through MS Excel program.
Statistical data analysis
All the tests were conducted in triplicate and the values were tabulated as mean ± S.E.M. Significant difference of the percent inhibition of various test samples was analyzed via two way ANOVA following Bonferroni’s post test using GraphPad Prism software in which the P < 0.05 were considered significant.
Results and discussion
In the current investigational study the radical scavenging potential of volatile oil was studied based on spectrophotometric analysis. The sources of free radicals employed were DPPH and ABTS, which have maximum absorbance values at 517 nm and 745 nm respectively. After getting scavenged by antioxidant compounds the colors of DPPH (violet) and ABTS (blue) solution change into yellow. Change in the color results in decrease of absorbance values which is directly proportional to the amount of radical scavenging compounds in the solution [32, 33].
Similarly, the anticholinesterase activity is based on the hydrolysis of acetylthiocholine iodide and butyrylcholine iodide by the formation of the yellow 5-thio-2- nitrobenzoate anion as a result of the reaction of DTNB with thiocholines, catalyzed by enzymes at a wavelength of 412 nm using spectrophotometer or microplate reader. Acetylthiocholine iodide and butyrylthiocholine iodide work as substrate of the reaction, while the DTNB is utilized for the measurement of cholinesterase activity. The percent inhibition of enzymatic activity is calculated from the rate of change in absorption of the reaction mixture .
Anticholinesterase activity of essential oil of Rumex hastatus at various concentrations
54.32 ± 1.33
61.64 ± 1.60
67.26 ± 1.24
71.70 ± 1.63
74.90 ± 0.52
46.32 ± 3.50
52.73 ± 0.78
57.00 ± 2.80
66.33 ± 0.49
71.32 ± 4.8
72.08 ± 1.04
78.58 ± 1.12
83.70 ± 1.60
89.00 ± 1.15
96.65 ± 1.34
66.87 ± 1.27
73.67 ± 0.88
79.95 ± 2.01
86.62 ± 1.67
91.61 ± 0.43
Parameters of various components of essential oil of Rumex hastatus
Area Sum %
Base Peak m/z
1E + 06
3E + 06
List of components of essential oil of Rumexhastatus
Pentanoic acid, 4-oxo
Ethanethioic acid, S-(2-methylpropyl) ester
1-Decyne (CAS) $$ Octylacetylene
ETHYL AMYL CARBINOL
2-Pentenoic acid, 4-hydroxy
Nonanoic acid, 9-oxo-, methyl ester
Octanoic acid, 8-hydroxy
3-Hexen-1-ol, benzoate, (Z)
Nonanedioic acid, monomethyl ester
(. + -.)-2-Methyl-6-p-tolyl-4-heptanol (diastereoisomer II)
Octanoic acid, 6,6-dimethoxy-, methyl ester
1,3-Dioxolane-4,5-dicarboxylic acid, 2,2-dimethyl-, dimethyl ester
Farnesyl Acetone C
9,19-Cycloergost-24(28)-en-3-ol, 4,14-dimethyl-, acetate
Hexadecanoic acid, methyl ester
Cyclobutanecarboxylic acid, 2-methyloct-5-yn-4-yl ester
beta.-Ionol $$ 3-Buten-2-ol, 4-(2,6,6-trimethyl-1-cyclohexen-1-yl)-
1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester
4-Allyl-1-ethoxy-3-phenylbenzo[c]-(1,2)-oxaphosphinine - 1-Oxide
4-Methyl-7-ethylizidine $$ 8-Methyl-5-ethylindolizidine
Essential oil isolated for the first time from the R. hastatus and its chemical composition demonstrates that R. hastatus is a source of valuable volatile components. Based on the anticholinesterase and antioxidant results of essential oil, it can be concluded that R. hastatus plant may be an effective source of compounds which may lead to possible palliative therapy and cure of oxidative stresses and neurodegenerative diseases.
All authors are thankful to Dr. Ali Hazrat, Department of Botany, Shaheed Benazir Bhutto University Sheringal, Dir (U), Pakistan for the identification of plant.
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