Phytotoxic studies of naphthoquinone intermediates from the synthesis of the natural product Naphthotectone

1,4-Naphthoquinones exhibit strong activity as antimalarial, antibacterial, antifungal and anticancer agents. These kinds of compounds have also shown phytotoxic activity. The first example of an allelochemical to be described was naphthoquinone juglone (5-hydroxy-1,4-naphthoquinone). This fact led us to conduct a study of the phytotoxic activity and structure–activity relationships of 26 naphthazarin derivatives. The compounds belong to two main groups, 5,8-dioxygenated-1,4-naphthoquinones and 1,4,5,8-tetraoxygenated naphthalenes with different functionalizations and chains at positions 2, 4, 6 and 7. The results show that substitution with halogens and modification of the hydroxyl groups on the aromatic ring with methoxy or acetate groups seems to play an important role in enhancing the activity.