Methanol extract of Cola nitida ameliorates inflammation and nociception in experimental animals

Abstract

Methanol extract of Cola nitida (MECN) was evaluated for its anti-inflammatory and analgesic activities using rats and mice. Inflammatory activity of MECN was assessed by carrageenan-induced paw oedema while analgesic activity was evaluated by acetic acid -induced writhing and formalin paw lick test. Histological analyses of the paws were also carried out. There was evaluation of the mechanism(s) of action of MECN using naloxone, a blocker of opioid receptors; atropine, blocker of muscarinic receptors; and propranolol, blocker of beta adrenergic receptors. Findings from the study revealed that MECN has both anti-inflammatory and analgesic properties. These properties were found to be dose dependent with 200 mg/kg of MECN discovered to be the most potent dose. 200 mg/kg was able to cause statistically significant reduction in paw size (p < 0.001) when compared with the carrageenan group. Histological analysis revealed that rats treated with 200 mg/kg of MECN showed no inflammatory cells in the left paw compared to other groups treated with carrageenan. In the formalin test, the number of paw licking was significantly reduced by MECN at 50 mg/kg, 100 mg/kg and 200 mg/kg in both neurogenic and inflammatory pain responses (p < 0.001) even as 200 mg/kg showed the highest percentage inhibition of 98.17% while 100 mg/kg of aspirin showed percentage inhibition of 93.66%. In acetic acid-induced writhing test, 50 mg/kg, 100 mg/kg and 200 mg/kg of MECN produced significant inhibition of writhes when compared with control as highest inhibition is observed in mice that received 200 mg/kg which is similar to aspirin. Administration of propranolol and naloxone was unable to reverse the analgesic function of MECN. However, atropine administration blocked the analgesic function of MECN. This shows that MECN exhibits its analgesic property through cholinergic pathway and not opioid and adrenergic pathways. Phytochemical screening revealed that MECN contains flavonoids, steroids, saponins, tannins, anthraquinines, terpenoids, and alkanoids. These phytochemical contents may thus be responsible for its analgesic and anti-inflammatory properties.

Keywords: Analgesic; Anti-inflammation; Carrageenan; Cola nitida.

Graphical abstract

Fig. 1

Carrageenan group received 10 ml of normal saline and 0.1 ml of 1% carrageenan (n = 6). 50 mg/kg MECN group received 50 mg/kg of MECN and 0.1 ml of 1% carrageenan (n = 6). 100 mg/kg MECN group received 100 mg/kg of MECN and 0.1 ml of 1% carrageenan (n = 6). 200 mg/kg MECN group received 200 mg/kg of MECN and 0.1 ml of 1% carrageenan (n = 6). Ibuprofen group received 10 mg/kg of ibuprofen and 0.1 ml of 1% carrageenan (n = 6). Carrageenan group showed presence of inflammatory edema (red arrows) and necrotic cells (black cells) (H & E, 400×). 50 mg/kg MECN group shows paw tissue with moderate amounts of mononuclear inflammatory cells enmeshed between the dense connective tissue of the dermis with mild inflammatory edema (red arrow) (H & E, 400×). 100 mg/kg MECN group have paw tissue with moderate amounts of polymorphonuclear inflammatory cells just below the dermis are perifollicular regions (H & E, 400×). 200 mg/kg MECN group have dermis consisting of closely-packed dense connective tissue with the absence of inflammatory cells (H&E, 400×). The ibuprofen group have paw tissue closely-packed dense fibrous connective tissue with no inflammatory cells (H & E, 400×).(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Effect of doses of MECN on formalin-induced paw licking time in mice. Values were expressed as mean ± SEM, N = 6 in each group. ^****p < 0.001, compared to control group. Control group received 10 ml of normal saline and 20 μl of 1% formalin (n = 6). 50 mg/kg MECN group received 50 mg/kg of MECN and 20 μl of 1% formalin (n = 6). 100 mg/kg MECN group received 100 mg/kg of MECN and 20 μl of 1% formalin (n = 6). 200 mg/kg MECN group received 200 mg/kg of MECN and 20 μl of 1% formalin (n = 6). Aspirin group received 100 mg/kg aspirin and 20 μl of 1% formalin (n = 6).

Fig. 3

Effect of Atropine on anti-nociceptive action of Cola nitida methanol extract. Values are expressed as mean ± SEM, n = 6 in each group. ^****P < 0.001, compared with the control. Group 1 received 10 ml/kg of distilled water and 20 μl of 1% formalin (n = 6). Group 2 received 200 mg/kg of MECN and 20 μl of 1% formalin (n = 6). Group 3 received 10 ml/kg distilled water, 200 mg/kg of MECN and 20 μl of 1% formalin (n = 6). Group 4 received 2 mg/kg of atropine, 200 mg/kg of MECN and 20 μl of 1% formalin (n = 6). Aspirin group received 200 mg/kg aspirin and 20 μl of 1% formalin (n = 6).