Thymoquinone

Thymoquinone (TQ) is a naturally occurring benzoquinone and the principal bioactive constituent of Nigella sativa seed oil, commonly known as black seed or black cumin. It is a substituted 1,4-benzoquinone; its molecular formula is C10H12O2 and a molecular weight of about 164.2 g/mol. The IUPAC name is 2-isopropyl-5-methyl-1,4-benzoquinone.

Natural occurrence and isolation: TQ is one of the major phenolic compounds in Nigella sativa seeds and their oil. It is typically isolated and purified using chromatographic methods.

Biological activities: In preclinical studies, thymoquinone exhibits antioxidant, anti-inflammatory, and anti-neoplastic properties. Proposed mechanisms include scavenging of reactive oxygen species, inhibition of NF-kB signaling, downregulation of pro-inflammatory enzymes such as COX-2 and iNOS, and induction of mitochondrial-mediated apoptosis in certain cancer cell lines. Some work suggests potential neuroprotective and hepatoprotective effects as well.

Pharmacokinetics and safety: Thymoquinone is lipophilic with limited water solubility, leading to variable bioavailability; human pharmacokinetics are not fully characterized. Most evidence comes from in vitro or animal studies, and clinical data are limited and inconclusive. Reported adverse effects at high doses in animals highlight the need for caution; thymoquinone is not approved as a drug or as a therapy with established efficacy.

Research status: Thymoquinone remains an active area of exploratory research for cancer, inflammatory, neurodegenerative, and metabolic conditions. Well-designed clinical trials are needed to define safety, dosing, and potential therapeutic value.