Photosynthesis-Inhibiting Activity of Methoxy-substituted 3-Hydroxynaphthalene-2-carboxanilides

In this study a series of six 3-hydroxynaphthalene-2-carboxanilides, substituted on the anilide ring by combinations of methoxy-methoxy, methoxy-fluoro and methoxy-chloro groups at different positions, was prepared by microwave-assisted synthesis and characterized. The compounds were tested for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. The PET-inhibiting activity of the compounds was within a wide range, but rather moderate; the highest activity within the series of the compounds was determined for N-(3,5-dimehoxyphenyl)-3-hydroxynaphthalene-2-carboxamide (IC₅₀ = 24.5 µM). The compounds were found to inhibit PET in photosystem II.