Beta-lapachone, a quinone, is derived from lapachol (a naphthoquinone) which can be isolated from the lapacho tree (Tabebuia avellanedae), a member of the catalpa family (Bignoniaceae). Like camptothecin and topotecan, Β-lapachone inhibits DNA topoisomerase I. Researchers have found that this compound has promising anticancer and antiviral properties.

Topoisomerase inhibitors, including beta-lapachone, seem to be effective against several types of cancer, including lung, breast, colon and prostate cancers and malignant melanoma. The use of beta-lapachone in humans has been limited due to its toxicity. However, 3-allyl-beta-lapachone (a close chemical relative) has been found to have lower toxicity in cell culture tests, and therefore may prove to be more useful than beta-lapachone.

Beta-lapachone works by disrupting DNA replication. Topoisomerase I is an enzyme that unwinds the DNA that makes up the chromosomes. The chromosomes must be unwound in order for the cell to use the genetic information to synthesize proteins; beta-lapachone keeps the chromosomes wound tight, and so the cell can't make proteins. As a result, the cell stops growing. Because cancer cells grow and reproduce at a much faster rate than normal cells, they are more vulnerable to topoisomerase inhibition than are normal cells. Beta-lapachone also interferes with the replication of HIV-1, a virus that causes AIDS, thereby slowing the advancement of the disease.

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