Thymoquinone (FR-1185, CAS 490-91-5) or 2-isopropyl-5-methylbenzoquinone is a bright yellow, crystalline powder melting at about 44°C. It is readily available in small to medium quantities from Frinton Laboratories, Inc.

Thymoquinone represents the synthetic equivalent of the active ingredient of the plant Nigella sativa.  It is native to Asia and has been used since ancient times for the treatment of neural diseases such as epilepsy and also in some cases of cancer. Thymoquinone is mainly found in the seeds of N. sativa. There is evidence that extracts of the seeds have a temporary effect in reducing blood pressure and of lowering levels of triglycerides and LDL. More clear evidence is its effect in boosting the immune system. Animal studies have shown that N. sativa seed can stop the growth of tumor cells and reduce the incidence of tumors. However, the effects in humans are unclear.

There has been some evidence that these plant seeds and also thymoquinone itself have been effective in cases of asthma, rheumatoid arthritis and damage from radiation therapy. Thymoquinone itself has been given to children with epilepsy and has been shown to cause apoptosis in cancer cells.