玉米苗中DIMBOA与几种酚酸类物质抑菌活性比较

本文从室内培养的7日龄玉米幼苗中提取、分离、鉴定了抗性次生化合物丁布(2,4-d ihydroxy-7-m ethoxy-2H-1,4-benzoxazin-3(4H)-one,D IMBOA),并就该物质对玉米纹枯病病原菌立枯丝核菌(Rhizoctonia solani)的活性与三种酚酸类物质(阿魏酸、对羟基肉桂酸和咖啡酸)进行了离体比较研究。结果表明,丁布(D IMBOA),对立枯丝核菌有很强的生物活性,在浓度为50μg/mL时即可抑制立枯丝核菌菌丝的生长,抑制率为18.52%。阿魏酸、对羟基肉桂酸和咖啡酸,这三种酚酸在浓度250μg/mL时对立枯丝核菌菌丝的生长有抑制作用,抑制率分别为26.30%、8.50%和6.30%。不仅如此,丁布与对羟基肉桂酸之间、以及三种酚酸两两组合之间还存在一定的协同作用。在浓度相等的情况下,丁布与对羟基肉桂酸的等量混合液的抑菌率显著高于这两种物质单独存在时的抑菌率之和;同样,对羟基肉桂酸与阿魏酸的等量混合液的抑菌率比单一的对羟基肉桂酸溶液的抑菌率高18.89%,比单一的阿魏酸溶液的抑菌率高13.33%;对羟基肉桂酸与咖啡酸的等量混合液,抑菌率比两者单独试验时分别高9.63%和14.83%;阿魏酸与咖啡酸的混合液,抑菌率比两酸单独试验时分别高11.48%和22.23%。这一结果提示植物体内产生适当比例不同次生化合物的组合对植物抗病性的提高是至关重要的。     

The reduction of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one by thiols

2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), a naturally occurring hydroxamic acid involved in pest resistance of cereals, was reduced by thiols to the corresponding lactam. Kinetic studies showed that the reactive species are undissociated DIMBOA and thiolate anion. Possible mechanisms for the reaction are discussed in the light of relative reactivities of DIMBOA and a compound lacking the 7-methoxy substituent, and results from molecular orbital calculations.     

Quantitation of 1,4-Benzoxazin-3-ones in Maize by Gas-Liquid Chromatography

A gas-liquid chromatographic (GLC) procedure is reported for the quantitation of the trimethylsilyl (TMS) derivatives of substituted 2-hydroxy-2H-1,4-benzoxazin-3(4H)-ones (2-hydroxy-2H-1,4-benzoxazin-3(4H)-one[HBOA]; 2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one[HMBOA];2,4- dihydroxy-2H-1,4-benzoxazin-3(4H)-one[DIBOA]; 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one[DIMBOA]; and 2,4-dihydroxy-7,8-dimethoxy-2H-1,4-benzoxazin-3(4H)-one[DIM ₂BOA]) found in maize (Zea mays L.) extracts. Derivatized samples were chromatographed on columns with liquid phases of 2% DC-11 and 3% OV-17 and detected by flame ionization. Internal standards were methyl palmitate and methyl stearate on DC-11 and methyl behenate on OV-17. Detector response was linear to at least 5 nanomoles for TMS₂-HBOA and TMS₂-DIBOA and to 19 nanomoles for TMS₂-DIMBOA. Standard errors of 2% or less were obtained when four replicate samples were analyzed. For each of the 15 maize lines examined, the amount of DIMBOA determined by GLC was directly proportional to the amount of ferric chloride-reactive material determined colorimetrically.     

Auxin-induced elongation of short maize coleoptile segments is supported by 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one

Endogenous extractable factors associated with auxin action in plant tissues were investigated, especially their effects on elongation of 1-mm coleoptile segments of maize (Zea mays L.), in the presence of saturating 10 μM indole-3-acetic acid (IAA). The relative growth response, to auxin alone, was much smaller in segments shorter than 2–3 mm compared to 10-mm segments. Fusicoccin-induced elongation, however, was less affected by shortening the segments. A reduced auxin response may result from the depletion through cut surfaces of a substance required for IAA-mediated growth. Sucrose, phenolics like flavonoids, and vitamins were ruled out as the causal factors. A partially purified methanol extract of maize coleoptiles supported long-term, auxin-controlled elongation. The active material was also found among substances bleeding from scrubbed maize coleoptiles. The active factor from maize was further purified by HPLC and characterised by the UV spectrum and its pH shift. This factor was identified as 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) by mass spectroscopy. Activity tests confirmed that pure DIMBOA from other sources sustained auxin-induced elongation of short maize coleoptile segments. However, DIMBOA only partially restored the activity lost from short segments. This indicates that an additional factor, other than DIMBOA, is required. Extracts from Avena or Cucurbita did not contain the factor DIMBOA; it was active on maize elongation, but not on Avena coleoptiles or Cucurbita hypocotyls. This narrow specificity and the lack of DIMBOA action in short-term tests with maize indicate that DIMBOA is not the general auxin cofactor but may specifically “spare” the co-auxin in maize. Received: 27 June 2000 / Accepted: 16 October 2000     

Terpenoids of Pinus strobus cortex tissue

The diterpenes, strobol, strobal, manoyl oxide, and cis- and trans-abienols, were isolated as major constituents of the extract of Pinus strobus L. cortex tissue. The known triterpene, 3β-methoxy-14-serraten-21-one, was also found. A polyprenol was isolated from the needle extractives.     

The effect of pH on the transformation of syringic and vanillic acids by the laccases of Rhizoctonia praticola and Trametes versicolor

Laccases (benzenediol: oxygen oxidoreductases, EC 1.10.3.2) from Rhizoctonia praticola and Trametes versicolor formed different products from syringic and vanillic acids at different pH values, but both enzymes generated the same chemicals at a particular pH. The products were separated by thin-layer and high-performance liquid chromatography. Four compounds were determined from syringic acid (m/z 168, 334, 350 and 486) at pH 6.9, but only two of these (m/z 168 and 334) were found at pH 3.5. In the case of vanillic acid two isomeric dimers (m/z 304) and 2-methoxy-1,4-benzoquinone (m/z 138) were identified. The dimers were formed at both pH values (pH 3.5 and 6.9), but 2-methoxy-1,4-benzoquinone appeared only at pH 3.5.     

<Emphasis Type="Italic">ScBx</Emphasis> gene based association analysis of hydroxamate content in rye (<Emphasis Type="Italic">Secale cereale</Emphasis> L.)

Hydroxamates (HX) are major secondary metabolites synthesized by rye and are responsible for some of the unique properties of this cereal, including good tolerance of biotic and abiotic stresses and allelopathy. Recently, five genes encoding enzymes taking part in HX biosynthesis have been sequenced and characterized, which was the starting point to undertake the present study. Association analysis of the content of six HX–HBOA (2-hydroxy-1,4-benzoxazin-3-one), GDIBOA (2,4-dihydroxy-1,4-benzoxazin-3(4H)-one glucoside), DIBOA (2,4-dihydroxy-1,4-benzoxazin-3(4H)-one), GDIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3(4H)-one glucoside), DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3(4H)-one) and MBOA (6-methoxy-benzoxazolin-2(3H)-one) in the above-ground parts of plants and roots was performed on a population consisting of 102 and 121 diverse inbred lines, in 2013 and 2014, respectively. Altogether, 48 single nucleotide polymorphisms (SNPs) were found to be associated with the content of at least one HX: 20 SNPs were associated with HX synthesized in the above-ground parts of rye plants (AG-SNP), and 28 were associated with HX synthesized in the roots (R-SNP). The highest number of SNPs was present in genes ScBx1 (9) and ScBx5 (11). The majority of SNPs were affected by environmental factors, except for two: ScBx4_1702 associated with GDIBOA and MBOA contents, and ScBx5_1105 associated with HBOA content in roots.     

Role of hydroxamic acids in the resistance of cereals to aphids

Hydroxamic acid concentration in Gramineae, both natural and incorporated, correlates with resistance to the aphid Metopolophium dirhodum. 2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one, a hydroxamic acid isolated from corn extracts, is deleterious to aphids fed on artificial diets. It is proposed that hydroxamic acids act as naturally-occurring protective factors against M. dirhodum.     

Enantiomers of 2-methyl- and 2,4-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid: Preparation by resolution,determination of absolute configuration,and Curtius rearrangement

Both enantiomers of 2-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid 2 and 2,4-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid 3 were prepared via resolution of the corresponding racemic carboxylic acids with (R)- and (S)-1-phenylethylamine, respectively. Absolute configuration of (−)-(R)-2-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylic acid was determined by X-ray crystallography. Curtius rearrangement of acyl azides prepared from enantiomers of these heterocyclic carboxylic acids carried out in benzyl alcohol afforded enantiomers of the corresponding benzyl carbamates, which upon hydrogenolysis gave racemic 2-amino-2-methyl-3,4-dihydro-2H-1,4-benzoxazin-3-one 4 and 2-amino-2,4-dimethyl-3,4-dihydro-2H-1,4h-benzoxazin-3-one 5. Chirality 10:791–799, 1998. © 1998 Wiley-Liss, Inc.     

Identification of 1,4-Benzoxazin-3-ones in Maize Extracts by Gas-Liquid Chromatography and Mass Spectrometry

Gas-liquid chromatography-mass spectrometry (GLC-MS) has been used for the separation, detection, and identification of 1,4-benzoxazin-3-ones (hydroxamic acids and lactams) and benzoxazolinones found in maize (Zea mays L.) extracts. Compounds of interest were partitioned into ethyl acetate from aqueous maize seedling extracts. For analysis by GLC-MS, trimethylsilyl derivatives were prepared, chromatographed on a column of 3% OV-1, and detected in the mass spectrometer. Mass spectra were obtained for all peaks present in extracts of four maize lines. A data comparison system was developed for relating unidentified spectra to the spectra of the reference compounds. Based on spectral comparisons, three hydroxamic acids (2,4-dihydroxy-2H-1, 4-benzoxazin-3(4H)-one; 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one; and 2,4-dihydroxy-7,8-dimethoxy-2H-1,4-benzoxazin-3(4H)-one), three lactams (2-hydroxy-2H-1,4-benzoxazin-3(4H)-one; 2,7-dihydroxy-2H-1,4-benzoxazin-3(4H)-one; and 2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one), one benzoxazolinone (6-methoxybenzoxazolinone), and two organic acids (malic and aconitic) were identified in the extracts. In addition, one other hydroxamic acid and one other related compound were tentatively identified based on mass spectral evidence.     

Near-isogenic lines for measuring phenotypic effects of DIMBOA-Glc methyltransferase activity in maize

Three O-methyltransferases (BX10a, b, c) catalyze the conversion of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc) to 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) in maize (Zea mays). Variation in benzoxazinoid accumulation and resistance to Rhopalosiphum maidis (corn leaf aphid) was attributed to a natural CACTA family transposon insertion that inactivates Bx10c. Whereas maize inbred line B73 has this transposon insertion, line CML277 does not. To characterize the phenotypic effects of DIMBOA-Glc methyltransferase activity, we created near-isogenic lines derived from B73 and CML277 that do or do not contain the transposon insertion. Bx10c inactivation causes high DIMBOA-Glc, low HDMBOA-Glc, and decreased aphid reproduction relative to near-isogenic lines that have a functional Bx10c gene. These results confirm the importance of this locus in maize aphid resistance. The availability of Bx10c near-isogenic lines will facilitate further research on the function of different benzoxazinoids and DIMBOA-Glc methyltransferase activity in maize defense against herbivores and pathogens.     

Hydroxamic acids affecting barley yellow dwarf virus transmission by the aphid Rhopalosiphum padi

2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), a hydroxamic acid (Hx) occurring in wheat, was shown to deter feeding by the aphid Rhopalosiphum padi (L.), and to reduce BYDV transmission to the plant. Dual choice tests with wheat leaves showed the preferential settlement of aphids on leaves with lower levels of DIMBOA. Electric monitoring of aphid feeding behaviour showed that in seedlings with higher DIMBOA levels fewer aphids reached the phloem and they needed longer times to contact a phloem vessel than in those with lower levels. When aphids carrying BYDV were allowed to feed on wheat cultivars with different DIMBOA levels, fewer plants were infected with BYDV in the higher DIMBOA cultivars than in the lower ones. Preliminary field experiments showed a tendency for wheat cultivars with higher Hx levels to be more tolerant to infection by BYDV than lower Hx level ones.     

2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one, an Inhibitor from Zea mays with Differential Activity against Soft Rotting Erwinia Species

[2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one] DIMBOA was extracted with ethyl acetate from acidified water homogenates of corn (Zea mays L.) seedlings. Pure DIMBOA or ethyl acetate extracts of corn tissue were added to bacterial growth medium at five concentrations (measured as hydroxamates). DIMBOA and corn extracts were more inhibitory to soft rot bacteria (Erwinia spp.) that are nonpathogenic to corn than to soft rot bacteria that are corn pathogens. The inhibitory activity of DIMBOA was similar to that of the ethyl acetate extracts. Both corn extracts and DIMBOA prolonged the lag phase of bacterial growth without significantly changing log phase growth rates. At various concentrations of the inhibitor, 50 to 100% of the activity of corn extracts inhibitory to different bacterial isolates was attributable to DIMBOA. Extracts of DIMBOA-deficient plants (genotype bxbx) were not inhibitory to Erwinia spp. It was concluded that DIMBOA is the major active component in those corn extracts which are inhibitory to soft rot Erwinia species.     

Copper(II) complexes of a hydroxamic acid from maize

The thermodynamics of formation for DIMBOA-Cu(II) complexes (where DIMBOA = 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-4H-one, a hydroxamic acid from maize) has been investigated in aqueous solutions by a potentiometric method. DIMBOA forms 1:1 and 1:2 chelates with Cu(II) at ionic strength 0.05 M (NaCl04). The stability constants measured were about 10⁵ and 10⁴ for the 1:1 and 1:2 complexes respectively, determined at 10, 20 and 30°. The contribution of ΔH and ΔS to the stability of complexes is examined and the pK values are compared with other ligands found in maize. Although DIMBOA has similar or higher constants to form copper complexes than other plant ligands, its possible role as a transport agent in maize remains to be established.     

Effects of DIMBOA on detoxification enzymes of the aphid Rhopalosiphum padi (Homoptera: aphididae)

The presence of glutathione transferases and esterase activity was investigated in Rhopalosiphum padi and the effects of the cereal hydroxamic acid, 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) on these detoxification enzymes was studied. Activity of glutathione S-transferases and general esterases was determined for adult aphids feeding on a natural diet lacking DIMBOA and on an artificial DIMBOA-containing diet for 48 hours. In vivo, DIMBOA in the diet inhibited the activities of esterases by 50-75% at all concentrations tested (0.5-4 mM). The activity of glutathione transferase was inhibited to a lesser extent (30%) at the higher concentrations of DIMBOA. In vitro, DIMBOA generally inhibited the activity of esterases with an IC(50) of 33 micro M, and had a slight inhibitory effect on glutathione S-transferases. These effects of DIMBOA could make the aphids vulnerable to electrophilic agents and insecticides which may be metabolized via esterases and GSTs. In cereals, therefore, DIMBOA may act by interfering with esterase- or GST-mediated detoxification of xenobiotics by aphids.     

Field Efficacy of Verticillium lecanii,Sex Pheromone,and Pheromone Analogs as Potential Management Agents for Soybean Cyst Nematode

A soybean cyst nematode sex pheromone (vanillic acid), chemical analogs of the pheromone, and the fungus Verticillium lecanii were applied in alginate prills (340 kg/ha) to microplots and small-scale field plots as potential management agents for Heterodera glycines on soybean. In 1991 microplot tests, treatment with V. lecanii, vanillic acid, syringic acid plus V. lecanii, or vanillic acid plus V. lecanii lowered midseason cyst numbers compared with the untreated susceptible cultivar control, autoclaved V. lecanii treatment, or aldicarb treatment, At-harvest cyst numbers were lowest with V. lecanii and with vanillic acid treatments. Aldicarb treatment reduced midseason cyst numbers in 1992. There were no differences among seed yields either year. In the field trials, numbers of cysts were reduced one or both years with aldicarb, ferulic acid, syringic acid, vanillic acid, or 4-hydroxy-3-methoxybenzonitfile treatments, or with a resistant cultivar, compared to an untreated susceptible cultivar. Highest yields were recorded after treatment with 4-hydroxy-3-methoxybenzonitrile (1991), methyl vanillate (1992), and aldicarb (1992). These studies indicate that some chemical analogs of vanillic acid have potential for use in soybean cyst nematode management schemes.     

3-methoxy-4,6-dihydroxymorphinandien-7-one,an alkaloid from Croton bonplandianum

A new alkaloid, 3-methoxy-4,6-dihydroxymorphinandien-7-one, and norsinoacutine have been isolated from extracts of Croton bonplandianum.     

Biotransformation of 2-Benzoxazolinone and 2-Hydroxy-1,4-Benzoxazin-3-one by Endophytic Fungi Isolated from Aphelandra tetragona

The biotransformation of the phytoanticipins 2-benzoxazolinone (BOA) and 2-hydroxy-1,4-benzoxazin-3-one (HBOA) by four endophytic fungi isolated from Aphelandra tetragona was studied. Using high-performance liquid chromatography-mass spectrometry, several new products of acylation, oxidation, reduction, hydrolysis, and nitration were identified. Fusarium sambucinum detoxified BOA and HBOA to N-(2-hydroxyphenyl)malonamic acid. Plectosporium tabacinum, Gliocladium cibotii, and Chaetosphaeria sp. transformed HBOA to 2-hydroxy-N-(2-hydroxyphenyl)acetamide, N-(2-hydroxyphenyl)acetamide, N-(2-hydroxy-5-nitrophenyl)acetamide, N-(2-hydroxy-3-nitrophenyl)acetamide, 2-amino-3H-phenoxazin-3-one, 2-acetylamino-3H-phenoxazin-3-one, and 2-(N-hydroxy)acetylamino-3H-phenoxazin-3-one. BOA was not degraded by these three fungal isolates. Using 2-hydroxy-N-(2-hydroxyphenyl)[¹³C₂]acetamide, it was shown that the metabolic pathway for HBOA and BOA degradation leads to o-aminophenol as a key intermediate.     

Alkaloids from Toddalia aculeata

Two alkaloids N-methyl-4-hydroxy-7-methoxy-3-(2,3-epoxy-3-methylbutyl)-1H-quinolin-2-one (1) and 3-(2,3-dihydroxy-3-methylbutyl)-4,7-dimethoxy-1-methyl-1H-quinolin-2-one (2a) have been isolated from CH(2)Cl(2):methanol (1:1) and methanol extracts of leaves and stems of Toddalia aculeata. Their structures along with that of 15 other compounds, of which three are isolated for the first time from genus Toddalia, were established by their detailed spectral studies including 2D NMR viz. (1)H-(1)H COSY, (1)H-(13)C COSY, and HMBC.     

Secondary metabolites from Mycosphaerella ligulicola

(+)-Epoxydon, together with the new (+)-epoxydon monoacetate, 3-methylidene-6-methoxy-1,4-benzodioxan-2-one and 2-(2-hydroxy-5-methoxyphenoxy)-acrylic acid, has been isolated and identified from the mycelium of Mycosphaerella ligulicola grown on Sabouraud-maltose 4 %-agar.