Chemical constituent(s), anti-inflammatory, anti-oxidant and anti-nociceptive activities of the roots Of Palisota Hirsuta K.Schum (Commelinaceae).

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February, 2012
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The roots of Palisota hirsuta are used in Ghana and other West African countries where the plant grows for the treatment of various disease conditions such as rheumatoid arthritis (other painful and inflammatory conditions), infertility in females, anaemia, dysentery etc. The current study seeks to evaluate the anti-inflammatory, analgesic and anti-oxidant properties of the ethanolic root extract of P.hirsuta, the methanolic and petroleum ether fractions thereof and the constituents isolated from these fractions using animal models. The carrageenan-induced foot oedema test in 7-day old chicks was used to assess the anti-inflammatory effect of the ethanolic extract, methanolic and petroleum ether fractions and all the isolated constituents. Diclofenac and dexamethasone were used as reference drugs for these assessments. The effect before the induction of inflammation (pre-emptive) paradigm was used for the assessment of inflammation. The analgesic (anti-nociceptive) effect of the ethanolic extract methanolic and petroleum ether fractions as well as the isolated constituents was assessed using the formalin-induced nociception test in the mice paw. The in vitro antioxidant properties of the isolates PH I, II, III, IV, V and VI were evaluated by using the lipid peroxidation assay, 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH) radical scavenging assay and reducing power test. The standard antioxidant n-propyl gallate was used as the reference antioxidant in all the assays (the anti-oxidant assays were carried on the isolates following qualitative tests with DPPH). As part of the current study, the structures of the isolated constituents were evaluated using Gas Chromatography coupled with Mass Spectrometer (GC/MS) and Nuclear Magnetic Resonance. The crude extract PHC, methanolic fraction PHM and the petroleum ether fraction PHE of P.hirsuta (30-300mg/kg, p.o) dose dependently reduced oedema with maximal effects of 64.01±10.90%, 72.91±4.06%, and 57.86±11.89% (prophylactic) respectively. The extract PHC (30-300mg kg-1, p.o) caused a dose-related inhibition of both phases (i.e. phase 1 and phase 2) of the formalin-induced nociception. The highest dose caused maximal inhibitions of 40.89±24.10% and 66.25±32.08%. The methanolic fraction; PHM (30-300mgkg-1, p.o), also produced maximal inhibitions of both phases by 72.00±15% and 61.00±41.97%. PHE, which is the petroleum ether fraction dose-dependently, inhibited both phases of the formalin-induced nociception. Maximal inhibitions of 45.02±29.81% and 80.50±4.62% were respectively produced by PHE. For the isolates, PH I, II, III, IV, V and VI, the maximal inhibitions produced are as follows; PH I: 55.08±14.90% and 63.57±25.91%, PH II: 90.86±6.407% and 67.47±20.84%, PH III: 57.87±8.43% and 79.90±7.05%, PH IV: 71.39±9.19% and 89.19±3.81%, PH V: 61.34±11.07% and 82.89±3.97%, PH VI: 70.14±8.60% and 86.18±7.42% of the licking time in the early and late phases. Morphine as the reference drug (positive control) reduced the duration of formalin evoked nociceptive behaviour by a maximum percentage of 92.49±4.679% in the early phase and 95.16±5.49% in the late phase of the test. The isolates (0.5-3mgml-1) exhibited a lipid peroxidation activity as per the IC50 in the following corresponding manner; PH I 0.260, PH II 0.295, PH III 1.545, PH IV 0.007, PH V 1.769 and PHVI 1.453.The n-propyl gallate (0.001-0.3mgml-1) showed a lipid peroxidation activity by an IC50 of 0.015. The relative anti-oxidative activity in the DPPH decolourization assay (DPPH scavenging activity) of isolates as defined by the IC50 produced by the isolates (0.5-3mgml-1) were correspondingly PH I—3.304; PH II—3.636; PH III—0.241; PH IV—0.880, PH V--- 4.414 and PH VI—0.163. For n-propyl gallate (0.01-0.3mgml-1) the IC50 was found to be 0.058 in the DPPH decolourization assay. The isolates showed reducing power potential by their EC50 values corresponding to PH I—5.874; PH II —5.122; PH III—5.238; PHIV—0.524, PH V 4.501 and PH VI—1.723. The reference antioxidant n-propyl gallate showed a reducing power by an EC50 of 1.723. The findings in all three antioxidant activity assays show that the isolates have potent antioxidant properties which might partly account for the anti-inflammatory and anti-nociceptive/analgesic activities. Spectral analyses resolved PH IV to be 20-Hydroxyecdysone, PH I to contain the fatty acids eicosanoic acid and ethyl stearate, PH II to be a mixture of trimethyl benzene, cymene and ethyl hexadecanoate (ethyl palmitate) and PH III to be a mixture of methyl palmitate and octadecanoic acid. The roots extract PHC, the methanolic fraction PHM and ether fraction PHE exhibited anti-inflammatory activity as well as anti-nociceptive activity. The isolates PH I, II, III, IV, V and VI showed both anti-inflammatory and anti-nociceptive activities. The isolates also showed anti-oxidant action. 20-Hydroxyecdysone was isolated for the first time from the roots of Palisota hirsuta.
A Thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the Degree of Doctor of Philosophy,