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M. Mazza, T. Modena / Il Farmaco 54 (1999) 339–345
10, 12), Citrullus 6ulgaris (water melon) (6, 7, 12),
Cucumis melo (melon) (5, 9), Fragaria chiloensis (straw-
berry) (5, 9), Gossypium hirsutum (cotton) (1–3, 6, 7, 9,
10, 12–15), Heliantus annuus (sunflower) (6, 7, 10, 12),
Hordeum 6ulgare (barley) (6, 7, 10, 12), Oryza sati6a (rice)
(1, 2, 4, 6–15), Pisum sati6um (pea) (6, 7, 12), Solanum
lycopersicum (tomato) (6, 7, 10, 12), Glycine max (soy-
bean) (1–15), Sorghum (sorghum) (6, 7, 12), Triticum
aesti6um (wheat) (1–15), Vigna unguiculata (green dwarf
bean) (6, 7, 12) and Zea mais (maize) (4–12).
The herbicidal activities were evaluated in comparison
with those of the commercially available products used
as the reference standards: Trifluralin or Pendimethalin
for pre-seeding application, Linuron for pre-emergence
application and Glyphosate for post-emergence applica-
tion.
The results of the herbicidal activity and of the
phytotoxicity are not reported. The activities of the
compounds (see Tables 2 and 3) are expressed in a
simplified approach, in terms of compounds which were
more active or phytotoxic, as active or phytotoxic as, or
less active than the standards against each weed or crop
and the dose of each assay. Compounds that were
completely inactive or non-phytotoxic in each assay are
not reported.
3.2.2. Pre-emergence assay
The 6, 7, 10, 12, 14 derivatives at the lowest dose of
the assay showed activities higher or of the same order
as the reference standard against most weeds; A.
theophrasti, A. retroflexus, C. bursa-pastoris, M.
chamomilla and S. media were sensitive to the same
compounds at higher doses. Moreover, the 2, 2,3-Me2-
phenyl 4, 5, 8, 9 and 11 derivatives at the highest doses
of the assay were active against A. retroflexus, C.
bursa-pastoris, C. album, G. aparine, M. chamomilla, S.
nigrum and V. tricolor.
3.2.3. Post-emergence assay
Derivatives 6, 7, 10 and 14 showed higher or similar
activities as the reference standard at the lowest dose of
the assay against A. theophrasti, A. majus, C. bursa-pas-
toris, G. aparine, S. media; moreover, the same deriva-
tives, as well as compounds 2, 5, 9, 11 and 12, were
effective at higher doses against A. retroflexus, C. album,
M. chamomilla, S. nigrum and V. tricolor.
3.3. Crops
As far as phytotoxicity is concerned, results on the
most sensitive crops, reported in Table 3, show that many
compounds possessing herbicidal activity are also phyto-
toxic and, in many cases, the derivatives examined
possess toxicities of the same order or higher than the
reference standards. The derivatives 6, 7, 10 and 12
exhibited higher or the same phytotoxicity as the stan-
dards against most crops at low doses, except for T.
aesti6um. At higher doses, the same compounds, as well
as the derivatives 2, 9 and 14, were phytotoxic. Some
selectivity was shown by derivatives 6 and 12 against G.
herbaceum, by 6, 10 and 12 against H. 6ulgare, by 6, 7,
10, 12 against G. max and by 6, 10 and 12 against T.
aesti6um (unreported data).
3. Results
3.1. Monocotyledons
Monocotyledonous weeds generally show little sensi-
tivity to the compounds under examination. Only A.
myosuroides, A. ludo6iciana and E. crus-galli are affected,
as shown by their growth in the pre-emergence assay. The
most active compounds are the 3,4-Cl2-phenyl (6), 3,5-
Cl2-phenyl (7), 3-Br-4-Cl-phenyl (10) and 2-naphthyl (12)
derivatives. In pre-seeding assays, at the highest dose,
compounds 7 and 11 were as active as the reference
standard against A. ludo6iciana and E. crus-galli.
Higher persistence of the herbicidal effect was ob-
served for the more active compounds (halogenated 5–10
and naphthyl 11, 12 derivatives) in greenhouse than in
field tests.
3.2. Dicotyledons
4. Conclusions
Dicotyledonous weeds are generally much more af-
fected in their growth than monocotyledonous ones by
the compounds under examination.
The results reported in Tables 2 and 3 show that the
class of 2-substituted 1,3,4-(2H)-isoquinolinetriones pos-
sesses remarkable herbicidal activity. The compounds
examined may act by their intrinsic activity or as
pro-drugs giving either compounds C and D or com-
pounds E and F by a metabolic pathway.
The highest activities are related to the halogenated
and naphthyl derivatives.
The herbicidal activity is particularly remarkable
against dicotyledons, while monocotyledons are affected
in a lesser extent by treatment in pre- and post-emer-
gence. High sensitivity to the compounds tested was
3.2.1. Pre-seeding assay
Compounds 6, 7, 10, 12, as well as the 3-Cl-4-Me-
phenyl (9) and 3,4-Cl2-phenylmethyl (14) derivatives,
showed herbicidal activities higher or of the same order
as the reference standard against any weeds at the
minimal dose of the assay. At higher doses the 3-CF3-
phenyl 2, 2,3-Cl2-phenyl (5), 3-Cl-2-Me-phenyl (8) and
(11) derivatives were active against A. retroflexus, C.
bursa-pastoris, M. chamomilla and V. tricolor.