Anti-Inflammatory, Analgesic and Antioxidant Activities of the Methanol Extract and Solvent Fractions of Psychotria vogeliana Benth. (Rubiaceae) in Wistar Rats and Mice
Angela Odanibe Okpor, Chinonyelum Emmanuel Agbo, Collins Azubuike Onyeto, Chukwuemeka Sylvester Nworu*
- Department of Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Enugu State, Nigeria
| Key words:
Psychotria vogeliana; Rubiaceae; anti-inflammatory; analgesic; antioxidant; DPPH; arthritis.s
*Corresponding Author: chukwuemeka.nworu@unn.edu.ng
Page No: 375-387
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AbstractInflammation and pain remain leading causes of morbidity globally. Non-steroidal anti-inflammatory drugs and opioids, though widely used, are constrained by gastrointestinal, cardiovascular and dependence-related adverse effects. Psychotria vogeliana Benth. (Rubiaceae) is employed in Nigerian ethnomedicine for pain, bruises and inflammatory swellings. This traditional use, coupled with evidence of anti-inflammatory phytoconstituents within the genus, prompted its systematic pharmacological evaluation. This study therefore evaluated the analgesic, anti-inflammatory and antioxidant activities of the methanol extract and solvent fractions of the aerial parts of P. vogeliana. The methanol extract (ME) was obtained by cold maceration and sequentially partitioned into n-hexane (HF), ethyl acetate (EF) and methanol (MF) fractions. Acute oral toxicity was determined by Lorke’s method. Analgesic activity was assessed using the hot-water tail-immersion and acetic acid-induced writhing models in mice. Anti-inflammatory activity was evaluated via egg albumin-induced paw oedema, formaldehyde-induced arthritis and cotton pellet-induced granuloma models in rats. Antioxidant potential of the most active fraction (EF) was quantified by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferrous ion chelating assays. ME contained tannins, flavonoids, steroids, terpenoids, saponins, carbohydrates, resins, proteins and phenolics; alkaloids were detected only in EF. The median lethal dose (LD₅₀) exceeded 5000 mg/kg. ME (100–400 mg/kg) produced dose-related but statistically non-significant increases in tail-flick latency, whereas acetic acid-induced writhing was reduced significantly and dose-dependently at 200 and 400 mg/kg (35.6% and 47.6% inhibition, respectively; P < 0.05). ME did not significantly suppress acute egg albumin-induced oedema. In formaldehyde-induced chronic arthritis, ME and EF at 400 mg/kg significantly reduced paw thickness at discrete time points (P < 0.05), with EF producing the greatest cumulative inhibition (9.5%) among the fractions. HF significantly and dose-dependently reduced granuloma dry weight (P < 0.05), although EF and ME produced numerically larger, non-significant reductions at 400 mg/kg. EF demonstrated potent antioxidant activity, with DPPH scavenging > 88% and Fe²⁺ chelation > 80% across 15.63–500 μg/mL, surpassing ascorbic acid at all concentrations. The extract and particularly its ethyl acetate fraction exhibit peripherally mediated analgesic, appreciable chronic anti-inflammatory and marked antioxidant activities, plausibly attributable to flavonoids, tannins and terpenoids constituents, thereby providing pharmacological credence for the ethnomedicinal use of P. vogeliana.
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