ANALGESIC, ANTI-INFLAMMATORY AND TOXICITY STUDIES ON METHANOLIC LEAF EXTRACT OF ROTHMANNIA LONGIFLORA SALISB (RUBIACEAE) IN RATS AND MICE

ABSTRACT

The herbalists in several African Countries have used Rothmannia longiflora decoctions as febrifugal and analgesic agent. The present study examined the analgesic, anti-inflammatory and toxicological profile of the methanolic extract of the plant in experimental animals.

The preliminary phytochemical screening of the methanolic leaf extract of R.longiflora was carried out and revealed the presence of cardiac glycoside, steroids/terpenoids, tannins, saponins, flavonoids and carbohydrates.

The acute toxic effect (median lethal dose values (LD50) of methanolic leaf extract of Rothmannia longiflora was carried out using Lork’s method in intraperitoneal and oral routes in mice and rats and were found to be above 5000mg/kg body weight.

The anti-nociceptive effects of the extract was studied using acetic acid induced writhing test in mice, hot plate test in mice and formalin induced pain in rats. The anti-inflammatory effect was studied using Carrageenan induced paw oedema in rats.

The extract at doses of 50-1000mg/kg significantly (P<0.05) inhibited the number of acetic acid-induced abdominal writhes in mice dose dependently. The highest inhibition of abdominal constriction (64.9%) observed at 1000mg/kg was greater than that of piroxicam (61.5%), the standard non-steroidal analgesic and anti-inflammatory drug used in the study.

The methanolic leaf extract at doses of 250-1000mg/kg R. longiflora significantly (P<0.05) and dose-dependently protected the mice against thermally induced pain stimulus in mice but there was no significant thermal protection with the dose of 50mg/kg.

The 500 and 1000mg/kg doses of R.longiflora extract offered more than 100 and 200% respectively while the standard drug (Morphine sulphate) offered more than 300% protection against thermally induced pain stimulus in mice.

There was no significant inhibition of both the neurogenic pain (early phase) and inflammatory pain (late phase) at 50mg/kg and 250mg/kg doses of the extract.

However, there was significant (P<0.05) inhibition of both the neurogenic (early phase) and inflammatory (late phase) pain dose dependently at 500mg/kg and 1000mg/kg with highest inhibition at 1000mg/kg (53.33%). The significant (P<0.05) inhibition of the standard drug (Morphine sulphate) at the late phase was 46.67%; this doubled that of the early phase which was 20%.