Antiproliferative activity of naphthoquinones and indane carboxylic acids from lapachol against a panel of human cancer cell lines

Lapachol (1) is a well-studied natural product isolated from plants of the Bignoniaceae family and demonstrates diverse biological effects. Historically, chemical transformation of the lapachol scaffold has yielded new derivatives with impressive biological activity and rich chemical diversity. β-lapachone (2), α-lapachone (3), and 2-acetylfuronaphthoquinone (4) are examples of analogs derived from lapachol that show superior antitumor activity compared with the natural product. In the present study, novel indane carboxylic acid: 2,2-dimethyl-2,3-dihydroindeno[1,2-b]pyran-4,5-dione (9) and methyl 5-hydroxy-2,2-dimethyl-2,3,4,5-tetrahydroindeno[1,2-b]pyran-5-carboxylate (10) and naphthoquinone derivatives were synthesized from lapachol with structural similarities to the antitumor lapachol derivatives. The synthesized compounds were evaluated for antiproliferative activities against a panel of human cancer cell lines including in vitro models for neuroblastoma, melanoma, glioblastoma, and non-small cell lung cancer. As expected, the most potent derivatives were those incorporating β-naphthoquinone and α-naphthoquinono[2,3-b]furan skeletons. Many of these compounds possessed nanomolar to single digit micromolar antiproliferative potency. However, the most interesting analog evaluated was the dione 9 with an indeno[1,2-b]pyran skeleton, which demonstrated potent cytotoxic activity. The current investigation identified several new lead compounds that could be used as starting points for anticancer drug discovery.