Tropolone is a seven-membered non-benzenoid aromatic compound, which is the precursor of many Azulene derivatives. Tropolone is a potent mushroom tyrosinase inhibitor with an IC50 value of 0.4 μM. Its inhibitory effect can be achieved by dialysis or excess CU2+ Reversa. Tropolone exhibits broad anti-viral and anti-fungal activity and is synergistic upon co-treatment with nucleos (t) ide analog drugs. Tropolone is a promising candidate for research in osteosarcoma[1][2][3][4].