Thymoquinone: Major Molecular Targets, Prominent Pharmacological Actions and Drug Delivery Concerns

The oil of black seed (Nigella sativa) has been used as a folk medicine to treat a number of physiological disorders such as epilepsy, gastric problems, allergic conditions and various hepato-biliary ailments. Despite being unaware of the underlying phenomena for the cure of these diseases, people especially in the Mediterranean region have been using this ancient herb since ages. Researches in the 20th century conducted with the aim of tracking molecular pathways of anti-oxidant and anti-inflammatory mechanisms disclosed a great deal of information pertaining to the structural-activity relationships. Rigorous studies revealed that the major active constituent of Nigella sativa oil (NSO) is Thymoquinone (THQ) which exerts the majority of pharmacological actions observed by the essential oil. Since then, a large number of investigator groups have identified numerous molecular pathways of almost all major diseases which can be cured by THQ. Being a phytochemical, THQ has a high lipophilicity which makes it a poorly soluble agent in aqueous fluids restricting its systemic bioavailability. Also, THQ is highly light and heat-sensitive which further complicates its successful formulation for drug delivery. This review thus offers an insight to adequately comprehend the large number of pharmacological actions along with general mechanisms and major molecular targets pertaining to THQ. Additionally, a section dealing with the application of nanotechnological approaches to appropriately deliver the drug to its intended site of action has been elaborated.