Anti-inflammatory, antioxidant, and immunomodulatory aspects of Nigella sativa for its preventive and bronchodilatory effects on obstructive respiratory diseases: A review of basic and clinical evidence

Nigella sativa (N. sativa) is one of the most widely used medicinal plants. It has been used as food additive, preservative, and an herbal remedy for different diseases from ancient time. In traditional medicine, many astonishing effects such as treatment and prevention of many diseases related to the respiratory, gastrointestinal, immune, and nervous system had been mentioned for N. sativa. In the last three decades, numerous research has been done to substantiate such folk properties, identifying plant-derived natural substances, and understanding their mechanisms of action in the body. N. sativa improves the action of antioxidant enzymes (catalase, glutathione peroxidase, and glutathione-S-transferase) and acts as a free radical scavenger. As an anti-cancer agent, its modulatory activity on molecular targets, including p53, p73, PTEN, STAT3, PPAR-g, activation of caspases, and generation of ROS had been demonstrated. As an anti-inflammatory and immunomodulatory agent, it suppresses inflammatory mediators, leukotrienes, prostaglandins, and B cell-mediated immune response while it balances Th1/Th2 ratio and potentiates T cell and natural killer cell-mediated immune response. We aimed to review literature and experimental data of scientific research about the basic and clinical evidence of N. sativa and its constituents on preventive (anti-inflammatory, antioxidant, and immunomodulatory) and relieving (bronchodilatory) effects on obstructive respiratory diseases.