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Herbicidal action of 2‐hydroxy‐3‐alkyl‐1,4‐naphthoquinones
Author(s) -
Jewess Philip J,
Higgins James,
Berry Kate J,
Moss Stephen R,
Boogaard Adrian B,
Khambay Bhupinder P S
Publication year - 2002
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.428
Subject(s) - substituent , chemistry , photosystem ii , stereochemistry , alkyl , partition coefficient , lipophilicity , biological activity , photosystem i , mode of action , enzyme , in vitro , biochemistry , organic chemistry , photosynthesis
Abstract The main mode of herbicidal activity of 2‐hydroxy‐3‐alkyl‐1,4‐naphthoquinones is shown to be inhibition of photosystem II (PSII). The herbicidal and in vitro activities have been measured and correlated with their (Log)octanol/water partition coefficients (Log K o/w ). The length of the 3‐ n ‐alkyl substituent for optimal activity differed between herbicidal and in vitro activity. The maximum in vitro activity was given by the nonyl to dodecyl homologues (Log K o/w between 6.54 and 8.12), whereas herbicidal activity peaked with the n ‐hexyl compound (Log K o/w = 4.95). The effect of chain branching was also investigated using isomeric pentyl analogues substituted at position 3. All exhibited similar levels of in vitro activities but herbicidal activities differed, albeit moderately, with the exception of one analogue that was much less phytotoxic. Other modes of action were also investigated using two representative compounds. They did not show any activity on photosystem I or mitochondrial complex I, or generate toxic oxygen radicals by redox cycling reactions. Only moderate activity was found against mitochondrial complex III from plants, in contrast to much higher corresponding activity using an insect enzyme. © 2002 Society of Chemical Industry