Background: Justicia pectoralis (fresh cut), family Acantheceae, is a herb that is native to central America and the Caribbean. A crude extract prepared from the leaves of Justicia pectoralis is commonly used in Jamaican ethnotraditional medicine to reduce difficulty in breathing and suppress wheezing in asthmatic individuals.
Objectives: To investigate the anti-inflammatory and antihistamine activity of an aqueous extract of Justicia pectoralis.
Method: In in vivo experiments, guinea pigs were sensitized by the method of Weinrich and Undem, 1987. The effect of water on the wheals was assessed in the control group, n = 4. The effect of 3.3 mg of the crude extract was noted in histamine-induced wheals over a period of three hours. The extract was injected via intraperitoneal injections. In in vitro experiments, 3.3 mg of crude sample was tested for its effectiveness against histamine-induced tracheal contraction caused by cumulative dosing of histamine.
Results: The crude extract was efficacious in reducing the formation of histamine-induced wheals (p < 0.05). Results obtained from in vitro studies indicated that the crude extract (3.3 mg) caused significant reduction in tracheal smooth muscle contraction resulting from cumulative doses of histamine (p < 0.05). However, as the histamine doses increased, fresh cut extract was not able to maintain inhibition of histamine-induced tracheal smooth muscle contraction. This is an indication that the extract showed competitive reversible antagonism, possibly at histamine receptors.
Conclusion: A crude extract of the leaves Justicia pectoralis reduced the formation of histamine-induced wheals in sensitized guinea pigs (p < 0.05) and also reduced histamine-induced tracheal smooth muscle contractions (p < 0.05). It blocked the effect of contraction produced by histamine in the airways; this property supports folklore claims for its use as an antihistamine.