• The Korean Journal of Pesticide Science
• /
• v.6 no.2
• /
• pp.58-63
• /
• 2002

New photodynamic herbicidal 2,3-dihydro-2,2,4,5,6-pentamethylbenzofuran-5-yl, (I) and 2,3-dihydro-2-ethyl-2,4,5,6-tetramethylbenzofuran-5-yl, (II) substituents in 6-benzofury-2-[1-( alkoxyimino )alkyl]-3 hydroxycyclohex-2-en-1-one derivatives were synthesized and their herbicidal activities against rice plant (Oryza sativa L.), barnyard grass (Echinochloa crus-galli) and pickerel weed (Monochoria vaginalis presl.) were measured under submerged pre and post-emergence conditions. Particularly, a series of (I) compounds showed good selective herbicidal activities between the 3 leaf stage of rice plant and barnyard grass at rates of $0.25{\sim}0.0007kg/ha$. The structure activity relationships (SAR) on the herbicidal activity with changing N-alkoxy groups were discussed quantitatively. According to the SAR results, it was expected that the selectivity factor between seed of rice plant and barnyard grass should be rely on the N-alkoxy groups with bigger dipole moment and bigger (or smaller) $B_3$ constant than optimal value $(B_3)_{opt.}=4.41{\AA}$. Compared with (I), the (II) substituents showed more superior herbicidal activities.

• Korean Journal of Weed Science
• /
• v.30 no.2
• /
• pp.143-152
• /
• 2010

Herbicidal characterisitcs of natural product chrysophanic acid were investigated in a greenhouse condition. At early- and middle-stage post-emergence treatments, several grasses and broadleaf weeds appeared to be very susceptible to chrysophanic acid. However, any significant herbicidal activity treated by pre-emergence did not occur at concentration ranges from 31.3 to 1,000 ug $mL^{-1}$. Herbicidal activity of chrysophanic acid estimated by visual injury for large crabgrass was much higher when applied at 7 to 14 days after seeding than at 21 and 28 days after seeding. By post-emergence treatment, chrysophanic acid caused very considerable phytotoxicity on several grasses and broadleaf crops. In herbicidal interaction experiments determined by Colby's method, the effect of chrysophanic acid and caryophyllene oxide tank-mixture showed very high synergistic activity. Although chrysophanic acid did not give any pre-emergence effect, herbicidal spectrum tended to be very wide and strong when treated by post-emergence. These results suggest that chrysophanic acid possesses a possible potential to develop as a natural herbicide.

• Applied Biological Chemistry
• /
• v.49 no.3
• /
• pp.238-242
• /
• 2006

The herbicidal activities against the pre-emergence of rice plant (Oryza sativa L.) and barnyard grass (Echinochloa crus-gall) with changing substituents $(R_1-R_4)$ of new 5-benzofuryl-2-[1-(alkoxyimino) alkyl]-3-hydroxycyclohex-2-en-1-one derivatives as substrate molecules were studied quantitatively using comparative molecular field analyses (CoMFA). The optimized CoMFA models (rice plant: A5 & barnyard grass: B3) were derived from atom based fit alignment and a combination of CoMFA fields. The two models for herbicidal activity against two plants showed the best predictability and fitness ($q^2$>0.6 & ${r^2}_{ncv.}$>0.94) for the herbicidal activities. Also, CoMFA-HINT contour maps showed that the selective herbicidal activity between rice plant and barnyard grass depends on the hydrophobicity of $R_2\;and\;R_3$ groups in molecule. Therefore, it is expected that the herbicidal activity against barnyard grass will be improved by the introduction of the steric bulk small and hydrophobic group.

• Applied Biological Chemistry
• /
• v.36 no.5
• /
• pp.381-386
• /
• 1993

New twenty five Imazethapyr derivatives, [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin -2-yl)-3-(N-methyl-N-X(sub.)-phenylaminooxoacetyl)-5-methylpyridine] were synthesized. and The quantitative structure activity relationships (QSARs) between their post-emergence herbicidal activity$(pI_{50})$ values in vivo against Barnyard grass (Echinochloa crus-galli) and physicochemical parameters of substituents(X) of 3-(N-methyl-N-X(sub.)-phenylaminooxoacetyl) group have been studied. From the basis on the findings, in case of post-emergence, the activities were dependent on the steric constant$(E_s<0)$ and electron donating $(\sigma<0)$ effect by subsitituents(X) of 3-(N-methyl-N-X(sub.)phenylaminooxoacetyl) group. Therefore, The most effective compound,15 (4-t-butyl group) and 20 (3,5-dimethyl group) were examined in this study. And the conditions on the compounds predicted to show higher herbicidal activity were also discussed.

• Applied Biological Chemistry
• /
• v.37 no.6
• /
• pp.516-521
• /
• 1994

New seventeen imazapyr derivatives, 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-3-(N-methyl-N-X(sub.)-phenylaminooxoacetyl)pyridine, 6 were synthesized and their pre-emergence herbicidal activity$(pI_{50})$ in vivo against Corn (Zea mays L.) and Pigweed (Amaranthus viridis L.) were studied by the pot test under paddly conditions. Quantitative structure activity relationships (QSARs) were analyzed using the physicochemical parameters of substituent(X) on the phenyl ring of 3-(N-methyl-N-X(sub.)-phenylaminooxoacetyl) group and regression analysis. The herbicidal activities were related to the steric effect of X-substituent. The effect was rationalized by paraholic function of MR and $L_1$, where the optimal values were MR=5.56 (Zea mays L.) and $L_1=3.34\;{{\AA}}$ (Amaranthus viridis L.). Among them, 2,5-difluoro substituted compound, 6i showed good herbicidal activity against Pigweed with excellent tolerance to Corn.

• The Korean Journal of Pesticide Science
• /
• v.4 no.2
• /
• pp.32-36
• /
• 2000

A series of synthesized N-(2-fluoro-4-chloro-5-alkyloxyphenyl)-3,4-dimethyl-2-arylthio-5-oxo-2,5-dihydropyrrole derivatives as substrates were found to selectivity significantly with both rice plant (Oryza sativa L.) and weeds, barnyard grass (Echinochloa crus-galli) and bulrush (Scriptus juncoides) for those herbicidal activities at a rate of 0.1 kg/ha with post emergence under submerged conditions. The structure activity relationships (SARs) on herbicidal activity of $SR_{2}$=2-arylthio substituents on the pyrrole ring were analysized. From the results, the relative contribute orders of the $SR_{2}$ with phenyl group on the activity are meta > para > ortho-substituents. Among these compounds, the $R_{1}=propargyl$ (IA) subsrituents, $1{\sim}12$ showed higher activity than the $R_{1}$=2-chloro-2-propenyl (IB) substituents, $13{\sim}16$. The $SR_{2}$ groups of IA substituents shown that the optimal steric constant, $(Es)_{opt.}=3.25$ and m-phenylthio substituents were found to be -contribute the activity against barnyard grass. But the herbicidal activity of IB substituents against bulrush would depend upon the molar refractivity, $M_{R}$ constant of $SR_{2}$ group.

• The Korean Journal of Pesticide Science
• /
• v.9 no.2
• /
• pp.173-180
• /
• 2005

This study was conducted of Korean native plants to screen herbicidal activity which could be used for the development of new natural herbicides. Eighty-one plants were collected from Wan and Juju islands in Korea and their methanol extracts were obtained. Heibicidal activities of the methanol extracts were determined by seed bioassay using rapeseed (Brassica napus L.) seedlings. Among eighty-one species, eleven plants were highly herbicidal ($GR_{50}$ < 1,000 ${\mu}g\;g^{-1}$): Abies koreana WILS., Anthemis nobilis L., Callicarpa mollis SIEB. et ZUCC., Cirsium setidens, Euonymus maackii RUPR., Euphorbia jolkini BOISS., Kadsura japonica DUNAL, Paeonia aliflora Pall var. tricocarpa BUNGE, Philadelphus tenuifolius RUPR. et MAXIM., Sapium sebiferum, Vicia angustifolia var. segetilis K. KOCH. Fifty plants were shown moderate herbicidal activity (1,000 ${\mu}g\;g^{-1}$ < $GR_{50}$ < 2,000 ${\mu}g\;g^{-1}$), however, twenty plants were not shown any herbicidal activity.

• The Korean Journal of Pesticide Science
• /
• v.9 no.4
• /
• pp.279-286
• /
• 2005

The herbicidal activities against pre-emergence barnyard grass (Echinochloa crus-galli) by a series of new 2-(4-(6-chloro-2-benzoxazolyloxy)phenoxy)-N-phenylpopionamide derivatives as substrate molecule were studied using molecular holographic (H) quantitative structure activity relationships (HQSAR) methodology. From the based on the findings, the higher herbicidal active compounds are predicted by the derived HQSAR model. The best HQSAR model (VI-1) was derived from fragment distinction combination of atoms/bonds in fragment size, $7{\sim}10$bin. The herbicidal activities from atomic contribution maps showed that the activity will be able to increased according to the R-substituents variation of the N-phenyl ring and change of 6-chloro-2-benzoxazolyloxy group. Based on the results, the statistical results of the best HQSAR model (VI-1) exhibited the best pedictability and fitness for the herbicidal activities based on the cross-validated value ($q^2=0.646$) and non cross-validated value ($r^2_{ncv.}=0.917$), respectively. From the graphical analyses of atomic contribution maps, it was revealed that the lowest herbicidal activitics depends upon the 4-(6-chloro-2-benzoxazolyloxy)phenoxy group ($pred.pI_{50}=-3.20$). Particularly, the R=4-fluoro, X=isobutoxy substituent (P2) of (X)-phenoxy-N-(R)-phenylpropionamide derivative is predicted as the highest active compound ($pred.pI_{50}=9.12$).

• Weed & Turfgrass Science
• /
• v.1 no.4
• /
• pp.44-49
• /
• 2012

The objective of this study was to know the herbicidal activity of the essential oil from amyris (Amyris balsamifera). In a seed bioassay experiment, the amyris essential oil inhibited the growth of rapeseed (Brassica napus) by fifty percent at 8.8 ${\mu}g\;g^{-1}$. And in a greenhouse experiment, sorghum, barnyard grass and Indian jointvetch, which was applied in above-ground parts, with the amyris essential oil at 4,000 ${\mu}g\;ml^{-1}$ showed visual injuries of 90, 70, and 70, respectively (0, no damage; 100, total damage). However, soil application of the essential oil did not show such herbicidal injuries. In a field experiment, foliar application of the amyris essential oil at 5% controlled effectively weeds such as barnyardgrass, shepherd's purse, and clover in 24 hours. Our results indicated that the amyris essential oil had herbicidal activity. To understand the composition of the amyris essential oil, the oil was analyzed by gas chromatography-mass spectometry with solid-phase micro-extraction apparatus. There were 15 organic chemicals in the oil and the major constituents were calarene, elemol, ${\gamma}$-eudesmol, curcumene, ${\beta}$-sesquiphellandrene, zingiberene, selina-3,7(11)-diene, 1,3-diisopropenyl-6-methyl-cyclohexene, ${\beta}$-bisabolene, and ${\beta}$-maaliene. Overall results suggest that the amyris essential oil had a herbicidal activity with fast, contact, and non-selective mechanism.

• The Korean Journal of Pesticide Science
• /
• v.4 no.3
• /
• pp.89-92
• /
• 2000

A series of 5-(2-metllyl-2-alkylindallyl)cyclohexane-1,3-diones were synthesized and evaluated for herbicidal activities in a green house. Under submerged paddy conditions, those compounds showed high herbicidal activity against barnyardgrass with good tolerance on rice.