The powder of sun-dried root barks of Dichrostachys cinerea is usually used in folk medicine for the treatment of asthma. The bark powder of Dichrostachys cinerea's root is used in nasal instillation.
In the present work, phytochemical investigation performed on the plant species collected in Libreville (Gabon) forest revealed the presence of bioactive compounds such as alkaloids, flavenoids, tannins, sterols and triterpenes, phenolic compounds. These results are in accordance with those showing the presence of terpenoids, sterols and tannins in the leaves and fruits. Pharmacological study showed a transient bronchoconstriction followed by a sustained bronchodilation in the airway smooth muscle. Similar results were demonstrated with Parquetina nigrescens (Periplocaceae) on smooth muscle preparations . These results suggest that constituents in the extract of D. cinerea may exert airways regulation.
It is well established that the salbutamol (β2-adrenergic receptor agonist) activity is due to the stimulation β-adrenergic receptors . The fact that D. cinerea-evoked biphasic action and mainly bronchodilatory effect was similar to that induced by salbutamol, allowed us to suggest that D. cinerea's active principles may act via β-adrenergic receptors to elicit the relaxation of the trachea smooth muscle. In the GPTPs, salbutamol produces more relaxant effect than salmeterol, suggesting that salmeterol is a partial beta-2 agonist. Very high concentrations of salmeterol as well of salbutamol may induce non-beta adrenoceptor mediated relaxation. There is no pronounced difference in the magnitude of antagonism against carbachol induced contractions between salmeterol and salbutamol . Since, the plant extract exhibited a direct relaxation of normal smooth muscles of the trachea  and in addition, it induced a concentration-dependent relaxation of the GPTPs pre-contracted with KCl or with histamine. However, D. cinerea hydro-alcoholic extract moderately reduced the bronchoconstriction evoked by acetylcholine. This result did not suggest a high inhibitory effect the plant extract actives principles on the cholinergic receptors. Since, ACh still induced a significant bronchoconstriction on the isolated trachea pre-treated with the plant extract; while atropine, an antagonist of cholinergic muscarinic receptors totally abolished the ACh-evoked at the same conditions. Indeed, the agonist of cholinergic receptors such as ACh evoked bronchospasm which is inhibited by anticholinergic drugs such as atropine . Anti-cholinergic drugs block muscarinic effect of ACh on the receptors of postjunctional membranes and so inhibit the answer of the post ganglionic parasympathetic nerve. The loss of M2 muscarinic receptor function occurs in asthmatics and it contributes to bronchial hyper -responsiveness and it is not a chronic feature of asthma, and instead it characterizes asthma exacerbation. The loss of M2 muscarinic receptor function in children and adults happens during antigen bronchoprovocation or during exposition of asthmatics to ozone. The research findings support the hypothesis that beta2-adrenoceptor agonist drugs, administered over time in vivo or in vitro, induce a transient hyperresponsiveness of airway smooth muscle to cholinergic bronchoconstrictor stimuli [29, 30]. Histamine-evoked broncho-constriction is due to the activation of H1-histaminergic receptors and is blocked by antihistaminergic drugs such as promethazine [31, 32]. Whereas, KCl-induced broncho-constriction results from the depolarization of cell membrane which causes the augmentation of calcium influx through voltage operated calcium channels leading to the rise of intracellular calcium level . Moreover, the acute and relatively refractory hyperkalemia can develop. In such situations, incorporating salbutamol with a conventional anti-hyperkalemia strategy can provide an effective therapeutic option to treat hyperkalemia, even during the anhepatic stage [34, 35]. Our study showed that, the plant extract, totally inhibited the KCl-evoked contractions and similarly to promethazine, it abolished histamine-evoked contractions suggesting the involvement of different possible mechanisms: a potassium channels opening effect, an inhibitory effect on calcium channels and/or an antagonistic effect on histaminergic receptors. Further studies are required to clarify the contribution of these mechanisms of action.
Pathophysiology of asthma is characterized by two phases, namely a bronchoconstriction followed by a special type inflammation ; the bronchoconstriction being the main component of the immediate phase of asthmatic response on multiple stimuli . Overall, the plant extract's actives principles-evoked relaxation on pre-contracted tracheal chains (pathological tissues) highlighted a bronchospasmolytic action that may support its potential usefulness in the treatment of bronchoconstrictive diseases. Regarding the phytochemical composition of the plant extract, active constituents in the plant extract such as terpenoids may be responsible for the bronchodilator action . In addition, flavonoids and polyphenols contents in plant extract may contribute for the biological activities of the extract and thus the therapeutic potential of D. cinerea for the management of asthma. Since, these phytoconstituents have spasmolytic action on smooth muscle [39, 40], antioxidant and anti-inflammatory activities [41, 42].
Promethazine or Edici associated to histamine induced a relaxation of the GPTPs smooth muscle. The Emax values were at half decrease. It is well known that promethazine is a phenothiazine used as an anti-histamine. Antihistamines such as promethazine compete with histamine for one of the receptors for histamine (the H1 receptor) on cells. Promethazine also blocks the action of acetylcholine (anticholinergic effect). The same observation was done with the interaction ACh-Atropine or ACh-Edici. The values of EC5 and EC50 were very influenced in the presence of our extract. Similar results were obtained with seeds aqueous extract from Acacia nilotica . Moreover, experiments with the stem bark of Mangifera indica Linn. showed similar results . Our experiments suggest that the aqueous extract of D. cinerea could block both the histaminic and muscarinic receptors on guinea-pig trachea.