An Evidence-Based Review of Antitussive Herbs Containing Essential Oils in Traditional Persian Medicine

BACKGROUND: Cough is one of the most common medical symptoms for which medical advice is sought. Although cough is a protective reflex responsible for clearing the airways from secretions and foreign bodies, it can be a troublesome symptom that causes discomfort to patients. Due to the increasing interest in herbal remedies in both developed and developing countries, in the current study, we aimed to overview medicinal herbs containing essential oils used as antitussive agents according to Traditional Persian Medicine (TPM) textbooks. We summarized the relevant scientific evidence on their possible pharmacological effects. METHODS: To collect the evidence for the treatment of cough or "seaal" (cough in ancient books) from TPM sources, five main medicinal Persian manuscripts were studied. The antitussive herbs were listed and their scientific names were identified and authenticated following botanical reference books. ScienceDirect and PubMed online databases were searched for related mechanisms of action of the reported medicinal plants. RESULTS: Forty-nine herbs containing essential oils have been recommended in TPM for the treatment of cough; 21 of them had at least one known mechanism of action for cough suppression in the scientific literature. According to this review, most of the cited medicinal plants were assessed for either nitric oxide inhibitory or antitussive/expectorant activities. CONCLUSION: In addition to advantageous effects of antitussive herbs recommended by TPM, the present review highlighted some recent evidence-based data on these promising herbs that could be used as an outline for future research on their medicinal use.