Pharmacological assessment of lupinus arboreus sims (fabaceae) methanol extract and three active constituents for antinociceptive and anti-inflammatory effects

Project Abstract

<p> The methanol extract and chemical constituents of Lupinus arboreus leaf were investigated<br>for antinociceptive and anti-inflammatory activities. The study was by experimental design.<br>the extract was partitioned to yield hexane, ethylacetate, and methanol fractions.<br>Phytochemical tests were done on the extract and fractions. Acute toxicity test (LD50) was<br>carried out on crude methanol leaf extract (CME). Extract hexane fraction (HEF),<br>ethylacetate fraction (EAF) and methanol fraction (MEF) were subjected to bioactivity<br>guided fractionation using mice tail immersion, hot plate, acetic acid- induced tests and<br>formaldehyde- and, egg albumin-induced rat paw oedema, as activity guide for<br>antinociceptive and anti-inflammatory studies respectively. The active constituents were<br>isolated by bioactivity-guided silica gel column chromatography eluted with gradient<br>mixtures. The isolated active compounds were characterized using a combination of<br>phytochemical analysis, m.p. determination, UV, IR, NMR and GC/MS spectral analyses.<br>The intraperitoneal (i.p) LD50 of the crude methanol extract was 84.85 mg/kg. Phytochemical<br>analysis of the methanol extract indicated the presence of steroids, flavonoids, glycosides,<br>terpenes and saponins. Tannin, resin, reducing sugar and protein were moderately present.<br>The hexane fraction contained steroids and terpenes while ethylacetate fraction contained<br>flavonoids and glycosides. Two active compounds AHF1 and AHF2 were obtained from the<br>hexane fraction while AEF1 was obtained from the ethyl acetate fraction. The AHF1<br>contained steroids. while AHF2 contained terpenes; AEF1 contained flavonoids. The crude<br>methanol extract (CME) (30 and 60 mg/kg,) i.p produced dose-related resistance against<br>thermal pain and significant (p&lt; 0.01) inhibition of pain. On acetic-induced writhing test<br>CME exhibited a dose- related antinociceptive activity with 71.13 and 47.80 % at 60 and 30<br>mg/kg respectively. Fractions HEF, and EAF exhibited significant (p &lt; 0.05) pain inhibition<br>of 73 and 64 % respectively while MEF produced 24 percent pain inhibition. AHF1 and<br>AHF2 fractionated from HEF significantly (p&lt; 0.05) exhibited pain inhibition of 75 and 71 %<br>respectively at 30 mg/kg. AEF1 (30 mg/kg) also significantly (p&lt; 0.05) inhibited pain reflex<br>by 71 %. In egg albumin-induced (acute) oedema in rats, CME (30 and 60 mg/kg) produced<br>a dose-related oedema inhibition of 81.10 and 91.50 % respectively at the 4th hour.<br>Similarly, the hexane fraction (HEF) and ethylacetate (EAF) at 60 mg/kg produced a<br>significant (p&lt; 0.05) oedema inhibition of 79 and 40 % respectively at 4th hour. The effect of<br>methanol fraction (MEF) (60 mg/kg) was not significant (p&gt; 0.05). The oedema inhibition<br>recorded by HEF and EAF were higher than the inhibition by aspirin (100 mg/kg). The CME<br>(30 and 60 mg/kg) significantly inhibited formaldehyde- induced arthritis, in a dose-related,<br>manner over a period of 4 hours (p&lt; 0.05) (68 and 69 % inhibition respectively). Both HEF<br>and EAF at 60 mg/kg i.p, significantly (p&lt; 0.05) inhibited the oedematous response to<br>formaldehyde-induced arthritis, causing 85.7 and 64.2 % inhibition respectively. The<br>inhibitory effects of the isolates AHF1, AHF2 and AEF1 on egg albumin-induced (acute)<br>oedema in rats (78; 72, and 66 % respectively) were significant and better than that of aspirin<br>(100 mg/kg) (46 %). The effect of AHF1, AHF2 and AEF1, (30 mg/kg i.p) on formaldehydeinduced<br>(chronic) oedema in rats were 79 %, 72 % and 65 % respectively. The isolated active<br>compounds were identified as stigmastene 3, 6-dione (AHF1), ursolic acid (AHF 2),<br>tetrahydroxyflavone-3a- rhamnoside (AEF1), and ellagic acid (AEF 2). In this study, the<br>extract and fractions of L. arboreus leaves exhibited antinociceptive effect in different<br>models of pain; and anti-inflammatory effects against both acute and chronic models of<br>inflammation. The isolated compounds AHF1, AHF2 and AEF 1 appear to be responsible for<br>the antinociceptive and anti-inflammatory effects. The compound AEF2 identified as ellagic<br>acid, known for its antimicrobial activity, was concomitantly isolated. These compounds<br>were isolated and characterized for the first time from L. arboreus. <br></p>

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