Horehound (Marrubium vulgare) and Respiratory support: evidence and sources

Pulmonary fibrosis (PF) remains one of the most serious pneumopathies whose diagnosis and physiopathogenesis are still poorly understood and no treatment has been shown to be effective. Recently, many studies have shown a renewed interest in plants thanks to their pharmacological potentials, like horehound, known, for its anti-inflammatory and antioxidant activities. The present study investigated the effects of the aqueous extract of horehound (Mae) on bleomycin (BLM)-induced PF in rats. Thirty rats were divided into three groups. The control group received no treatment, the BLM group received only intratracheally BLM (2 mg/kg), and the Mae group underwent administration of BLM+ Mae (2 mL/kg) daily for 20 days. Obtained results showed that Mae, rich in polyphenols, could significantly improve the damage caused by BLM by reducing the inflammatory index and the fibrosis score, bringing the lung structure of fibrotic rats close to that of control rats. As well, Mae obviously acted on the BLM inflammatory reaction, and the counting of bronchoalveolar lavage fluid (Balf) cells showed an increase in total cell number and a decrease in the infiltration of inflammatory cells in the bronchoalveolar space. In addition, the BLM instillation was accompanied by oxidative stress in the lung, liver, and kidney tissues, proven by an increase in lipid peroxidation, as well as through depletion of superoxide dismutase (SOD) and catalase (CAT). The Mae treatment reversed all disturbances of BLM-induced oxidative stress parameters promoting antioxidant and anti-inflammatory of the latter. These findings point to Mae as a promising candidate for the treatment of pulmonary fibrosis.

Aerial parts and the root of Marrubium vulgare L. (white horehound) have been traditionally used in Europe and in southern and eastern Mediterranean countries. During colonization, the plant was introduced in America to great levels of popularity because of the simplicity of its growing; it was especially popular in Mexico and Brazil, where it has been known as 'maromba', 'marroio' or 'marroio-branco'. Ethnopharmacological uses of M. vulgare include treating respiratory diseases such as acute or chronic bronchitis, colds and asthma. The plant is also used in cases where there is a lack of appetite or dyspepsia and for diagnosed type II diabetes. It has even been used for antihypertensive therapy. For decades, scientists have carried out extensive research trying to explain these and other pharmacologic actions. It is time to systematize and critically analyse the quality of results found to date. Copyright © 2016 John Wiley & Sons, Ltd.