Suk-Jin Koo

Methiozolin [5‐(2,6‐difluorobenzyl)oxymethyl‐5‐methyl‐3,3(3‐methylthiophen‐2‐yl)‐1,2‐isoxazoline], a new annual bluegrass (Poa annua L.) herbicide for turfgrasses

BACKGROUND Selective control of annual bluegrass (Poa annual L.) has been difficult in turfgrasses. The potential of methiozolin in this area was investigated. RESULTS Methiozolin was safe on established zoysiagrass (Zoysia japonica Steud.), creeping bentgrass (Agrostis palustris Huds.), Kentucky bluegrass (Poa pratensis L.), and perennial ryegrass (Lolium perenne L.) at 1000 g ha(-1) , and controlled annual bluegrass with GR50 values of 23, 52, 104, and 218 g ha(-1) at PRE, two-, four- and eight-leaf stage, respectively, in the greenhouse. When applied at early flowering, methiozolin suppressed >80% of annual bluegrass seed heads at 2000 g ha(-1) . (14) C-Methiozolin was readily absorbed by both leaves and roots, but translocation was mainly acropetal. No herbicidal activity resulted from application to the leaf only; however, application to the soil surface only showed equivalent herbicidal activity to that of broadcast application to the leaf and soil. Methiozolin at 500 to 1000 g ha(-1) provided 80 to 100% control of annual bluegrass when applied in the fall with acceptable and temporary injury to creeping bentgrass, and about 60% control when applied in the spring with no bentgrass injury in the field. CONCLUSION Methiozolin is an excellent candidate for annual bluegrass management in turfgrasses.

In Vivo Absorption, Distribution, Excretion, and Metabolism of a New Herbicide, Methiozolin, in Rats following Oral Administration

Methiozolin [5-(2,6-difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-1,2-isoxazoline] is a new turf herbicide that controls annual bluegrass in various cool- and warm-season turfgrasses. The present study is the first report elucidating absorption, tissue distribution, excretion, and metabolism of methiozolin in rats. The pharmacokinetic parameters in the blood were observed as follows: t(max) = 6 h, C(max) = 168.7 μg equiv/mL, t(½) = 49.4 h, AUC₁₂₀ = 9921.5 μg equiv·h/mL, and clearance = 39.2 mL/h/kg. Those parameters and the depletion curve for ¹⁴C in the plasma were very similar to those in the blood. Total excretion through urine and feces was 24.3 and 68.9%, respectively, during 120 h after administration; however, there was no excretion through expired air. The radioactivity excreted through bile was 40.1% of that administered. Excreted radioactivity peaked between 24 and 48 h, showing 51.0% of total excretion within 48 h. The orally administered ¹⁴C distributed across various tissues within 12 h after administration, showing 14.0% of the dosed, and was eliminated from all tissues without accumulation. Numerous minor metabolites (<4% of the dosed) in urine and fecal extract were detected within 72 h, and two of those were identified. The identified metabolites were Met-1 (glucuronic acid conjugate), 6-[5-(5-((2,6-difluorobenzyloxy)methyl)-4,5-dihydro-5-methylisoxazol-3-yl)-4-methylthiophen-2-yloxy]-tetrahydro-3,4,5-trihydroxy-2H-pyran-2-carboxylic acid, and Met-2, [2-(5-((2,6-difluorobenzyloxy)methyl)-4,5-dihydro-5-methylisoxazol-3-yl)thiophen-3-yl]methanol. Conclusively, methiozolin was shown to be readily absorbed in the gastrointestinal tract, distributed throughout the tissues within 12 h, metabolized extensively, and eliminated through urine and feces mostly within 48 h, without tissue accumulation.

Development of The New Turf Herbicide Methiozolin

Methiozolin (5-(2,6-difluoro-benzyloxymethyl)-5-methyl-3-(3-methyl- thiophen-2-yl)- 4,5-dihydro-isoxazole) is a new turf herbicide in isoxazoline chemistry. The herbicide controls grass weeds and has a high safety to various cool and warm season turfgrasses. This paper describes basic chemical, biological, and regulatory information of methiozolin.

Soil metabolism of [14C]methiozolin under aerobic and anaerobic flooded conditions.

Methiozolin is a new turf herbicide controlling annual bluegrass in various cool- and warm-season turfgrasses. This study was conducted to investigate the fate of methiozolin in soil under aerobic and anaerobic flooded conditions using two radiolabeled tracers, [benzyl-(14)C]- and [isoxazole-(14)C]methiozolin. The mass balance of applied radioactivity ranged from 91.7 to 104.5% in both soil conditions. In the soil under the aerobic condition, [(14)C]methiozolin degraded with time to remain by 17.9 and 15.9% of the applied in soil at 120 days after treatment (DAT). [(14)C]Carbon dioxide and the nonextractable radioactivity increased as the soil aged to reach up to 41.5 and 35.7% for [benzyl-(14)C]methiozolin at 120 DAT, respectively, but 36.1 and 39.8% for [isoxazole-(14)C]methiozolin, respectively, during the same period. The nonextractable residue was associated more with humin and fulvic acid fractions under the aerobic condition. No significant volatile products or metabolites were detected during this study. The half-life of [(14)C]methiozolin was approximately 49 days in the soil under the aerobic condition; however, it could not be estimated in the soil under the anaerobic flooded condition because [(14)C]methiozolin degradation was limited. On the basis of these results, methiozolin is considered to undergo fast degradation by aerobic microbes, but not by anaerobic microbes in soil.

Herbicidal Activity of d-Limonene to Burcucumber (Sciyos angulatus L.) with Potential as Natural Herbicide

The potential as natural herbicide of d-limonene natural agent was conducted on several weeds in a greenhouse and Sciyos angulatus in field condition. Herbicidal activity of foliar application at a concentration of 100 and 200 kg ai of d-limonene on seven weed species was completely killed in a greenhouse condition. Also, d-limonene at a concentration of 50 kg ai was completely killing on Abutilon theophrasti, Aeschynomene indica, Echinochloa crus-galli and Digitaria ciliaris 3 days after treatment. While pre-emergence treatment of d-limonene concentration of 12.5 to 200 kg ai showed not significant visible damages. Phytotoxic symptoms of d-limonene by foliar treatment were characterized by wilting and burn-down of leaves and stems followed by discoloration, finally, plant death. Crop selectivity at d-limonene concentration of 100 kg ai over to five main crops including Zea mays by foliar application was not at all. Field trial of foliar treatment with d-limonene 70 to 140 kg ai have effectively controled over 5~20 leaf stages of S. angulatus at the natural habitats. And herbicidal efficacy of foliar application on S. angulatus with carrier volume in field condition was increased with dose dependent manners. These results suggest that d-limonene is considered possible as herbicide, and may be further optimized for natural agent for environmental friendly natural herbicide.

Metabolism of a New Herbicide, [14C]Pyribenzoxim, in Rice

The in vivo metabolism of a new herbicide pyribenzoxim (benzophenone Ο-[2,6-bis(4,6-dimethoxypyrimidin-2-yloxy)benzoyl]oxime) in rice was carried out using container trials. Two radiolabeled forms of [carbonyl-(14)C]pyribenzoxim (P1) and [ring-(14)C(U)]pyribenzoxim (P2) were treated separately as formulations for foliar treatment by single applications of 50 g of active ingredient (ai)/ha at the 4-6 leaves stage. At 0, 7, 30, and 60 days after treatment (DAT), samples of panicle, foliage/rest of plant, and roots were taken for analysis. Upon harvest (120 DAT), rice plants were separated into grain, husk, straw, and root parts. Total radioactive residues (TRRs) at each sampling date were determined to show that the final radioactive residues at harvest were low in grain, husk, straw, and roots, accounting for <17 ppb. The concentration of final residues in the rice plant decreased rapidly, and less than 0.1% of initial TRRs remained at harvest. At 7 DAT, metabolite 1 [M1, 2,6-bis(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid] and two unknown compounds (other-1 and other-2) were detected in foliage extract, accounting for 3.5% TRRs (21.0 ppb), 3.1% TRRs (19.0 ppb), and 9.0% TRRs (54.3 ppb), respectively, while 26.1% of M1 was observed in solvent wash. Any other metabolites were not detected in the plant, including expected metabolite M3 (benzophenone oxime). On the basis of the results obtained, a metabolic pathway of pyribenzoxim in a rice plant was proposed.

Isolation of a New Herbicidal Compound Angelicin from Curly Dock (Rumex crispus L.)

인축 및 환경독성문제(Duke 1992)와 저항성 문제(Devine과 Shulka 2000)로 인한 수요둔화와 공급과잉으로부터 제초제 시장 확대의 어려움에 직면한 농약회사에서는 기개발된 제초제의 화학구조를 모방하는 me-too 방법, 유기화합물을 합성하고 살초검정을 통한 무작위 스크리닝 방법으로는 신물질을 개발하는데 한계가 있음을 인식하고 있으며(Benner 1993; Duke 등 2000; Pillmoore 등 1993), 이를 타개할 대안으로 천연물 유래 살초활성물질에서 찾고 있다(Vyvyan 2002). 우리나라에서도 2000년 초반부터 국내 자생식물로부터 살초활성식물을 탐색하는 실험이 진행되었고(김 2006) 애기수영(Rumex acetosella L.)으로부터 chrysophanic acid(김 등 2003a), 족도리(Asarum sieboldii Miq.)로부터 elemicin(김 등 2005), 삼지구엽초(Epimedium koreanum Nakai)로부터 methyl-p-hydroxybenzoate(임 등 2007), 할미꽃(Pulsatilla koreana Nakai)으로부터 anemonin(최 등 2003)과 5,6,7-trimethoxycoumarin (최 등 2008)이 분리된 바 있으나, 현재까지 이와 같은 식물기원 살초활성물질이 국내는 물론 국외의 농약회사에서 제초제 개발에 활용되고 있지는 않은 형편이다. 소리쟁이(Rumex crispus L.)는 우리나라 전역에서 자라는 마디풀과(Polygonaceae)의 다년생초본으로 높이 30-80cm이고 줄기는 곧추 자라며 줄기에서 달리는 잎은 호생하며 잎자루가 짧고 장타원상 피침형으로 양끝이 좁고 주름살이 있으며, 우리나라에는 소리쟁이와 형태학적으로 유사한 참소리쟁이(R. japonicus HOUTT), 묵밭소리쟁이(R. conglomeratus MURP.), 금소리쟁이(R. maritimus L.)도 서식하고 있다(이 2003). 민간에서는 잎을 식용으로 사용하고 있으며, 한방에서 소리쟁이의 잎과 뿌리는 우이대황엽, 우이대황이라하여 지혈, 통열, 해독, 통변, 기관지염, 변비 등의 다양한 처방제제로 활용되고 있다 (정과 신 1990). 최근에는 소리쟁이에 함유되어 있는 생리활성물질과 이의 생리작용에 대한 연구가 진행되고 있는데, 이 등(2007)은 소리쟁이 종자의 추출물이 소염진통작용 및 간보호 효과가 있는 것으로 보고한 바 있으며, 정 등(2006)은 소리쟁이 추출물이 Vivrio vulificus와 Saccaromyces cerevisiae에 대하여 항균활성을 나타내는 것으로 보고하였다. 그리고 소리쟁이에는 2,6-dichloro-4- nitrophenol, 2-isopropyl-5-methylphenol, 4-vinyl-2- methoxy-phenol, 2,3-dihydrobenzofuran와 같은 항산화물질이 존재하여(신 2001) BHA나 아스코르브산과 유사한 항산화활성을 나타내는 것으로 보고되기도 하였다. 소리쟁이 추출물은 살균 및 제초활성이 있어서 농약개발을 위한 선도화합물(mother compounds)을 제공할 수 있음이 보고되었는데 조 등(2002)은 소리쟁이에 함유된 chrysophanol, parietin, nepodin이 식물흰가루병 방제에 효과를 나타내는 것으로 보고하였다. 그리고 김 등(2003b)은 소리쟁이 MeOH 추출물이 유채에 대하여 살초활성을 나타내는 것으로 보고하였으나 현재까지 이에 함유된 살초활성물질에 대해서는 보고된 바가 없다. 본 연구의 목적은 소리쟁이에 함유된 살초활성물질을 분리하고, 그 화학구조를 밝히는데 있다.

Evaluation of Herbicidal Potential of Essential Oils and their Components under In vitro and Greenhouse Experiments

The present study aimed to evaluate the phytotoxic potential of essential oils. For this purpose, 18 essential oil samples extracted from Korean plants and 64 commercial essential oils were screened for their phytotoxic potential against the seedling growth of Brassica napus L. (rapeseed). Among the 82 samples, 11 commercial oils (cinnamon, citronella, clove, cumin seed, geranium, jasmine, lemongrass, palmarosa, pimento, rose otto and spearmint) strongly inhibited the seedling growth with GR 50 value −1 . Major components from these effective essential oils were identified by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS). GC-MS analyses revealed that the effective samples mainly consist of benzyl benzoate, carvone, citral, citronellol, eugenol, geraniol, D-limonene and terpinene. Subsequently, bioactivity of these individual components was evaluated against the seedling growth of B. napus, Echinochloa crus-galli and Aeschynomene indica. The components from different chemical groups exhibited different potency in inhibiting the seedling growth with varied GR 50 values ranged from 29 μg mL −1 to >1,000 μg mL − 1. In the greenhouse experiment, citral and geraniol completely suppressed the growth of all the tested 10 plants at 100 kg ha −1 . In conclusion, the individual essential oil components geraniol and citral could be used as natural herbicides for weed management.

Developmental toxicity assessment of the new turf herbicide, methiozolin ([5-(2,6-difluorobenzyl)oxymethyl-5-methyl-3,3(3-methylthiophen-2-yl)-1,2-isoxazoline]), in rabbits.

Methiozolin is a new herbicide to control annual bluegrass (Poa annua L.) and large crabgrass (Digitaria sanguinalis (L.) Scop.) in various turfgrasses. The potential of methiozolin to induce maternal and developmental toxicity was investigated in the pregnant New Zealand White Rabbits. Methiozolin was, at dose levels of 0, 125, 250 and 500 mg/kg/day, administered by oral gavage to artificially inseminated rabbits (25 females per group) from days 6 to 28 of gestation. All does were subjected to Cesarean section on day 29 of gestation. At 500 mg/kg/day, treatment-related toxicities including abortion (10/22), decreased mean body weight, weight gain, net body weight change, reduced food consumption and decreased fetal weight were observed. At 125 and 250 mg/kg/day, no signs of maternal and developmental toxicity were observed. There were no treatment-related external, visceral and skeletal abnormalities of fetuses at all doses tested. In the current experimental conditions, the no observed adverse effect levels (NOAELs) of methiozolin are considered to be 250 mg/kg/day for does and prenatal development.