α-Lapachone has antineoplastic activity, it shows an approximately trypanocidal activity against Trypanosoma cruzi.

The photophysical and photochemical reactions of β-lapachone were studied using femtosecond transient absorption, nanosecond transient absorption, and nanosecond time-resolved resonance Raman spectroscopy techniques and density functional theory calculations. In acetonitrile, β-lapachone underwent an efficient intersystem crossing to form the triplet state of β-lapachone. However, in water-rich solutions, the singlet state of β-lapachone was predominantly quenched by the photoinduced protonation of the carbonyl group at the β position (O9). After protonation, a series of fast reaction steps occurred to eventually generate the triplet state α±-lapachone intermediate. This triplet state of α±-lapachone then underwent intersystem crossing to produce the ground singlet state of α±-lapachone as the final product. 1,2-Naphthoquinone is examined in acetonitrile and water solutions in order to elucidate the important roles that water and the pyran ring play during the photoconversion from β-lapachone to α±-lapachone. β-Lapachone can also be converted to α±-lapachone in the ground state when a strong acid is added to an aqueous solution[1]