Mario R. Tellez

The inhibitory activity of natural products on plant p-hydroxyphenylpyruvate dioxygenase.

The inhibitory activity of 34 natural products of various structural classes on hydroxyphenylpyruvate dioxygenase (HPPD), the target site for triketone herbicides, and the mode of interaction of selected natural products were investigated. Recombinant HPPD from arabidopsis is sensitive to several classes of natural compounds including, in decreasing order of sensitivity, triketones, benzoquinones, naphthoquinones and anthraquinones. The triketone natural products acted as competitive tight-binding inhibitors, whereas the benzoquinones and naphthoquinones did not appear to bind tightly to HPPD. While these natural products may not have optimal structural features required for in vivo herbicidal activity, the differences in their kinetic behavior suggest that novel classes of HPPD inhibitors may be developed based on their structural backbones.

Differential accumulation of isoprenoids in glanded and glandless Artemisia annua L

Abstract The relative abundance of steam-distillable isoprenoids and other volatile compounds in leaves of glanded and glandless Artemisia annua L. was investigated. Steam distillation of leaves bearing glandular trichomes yielded 0.24% essential oil on a fresh weight basis. Monoterpenes were predominant in this essential oil, of which α -pinene (26.7%), pinocarvone (15.8%), and artemisia ketone (11.0%) were the major constituents. The essential oil distilled from glandless leaves amounted to 0.06% of fresh weight, and consisted mostly of sesquiterpenes, of which germacrene- D (49.8%) and β -caryophyllene (25.1%) were the major components. Only one monoterpene, β -ocimene, present in trace amounts, was detected in the oil distilled from the glandless tissue. The sesquiterpene artemisinin, found only in the glanded biotype, is heat-labile and cannot be extracted by steam distillation, during which it decomposes into non-distillable products.

Dehydrozaluzanin C, a natural sesquiterpenolide, causes rapid plasma membrane leakage

Abstract Dehydrozaluzanin C, a natural sesquiterpene lactone, is a weak plant growth inhibitor with an I50 of about 0.5 mM for lettuce root growth. It also causes rapid plasma membrane leakage in cucumber cotyledon discs. Dehydrozaluzanin C is more active at 50 μM than the same concentration of the herbicide acifluorfen. Symptoms include plasmolysis and the disruption of membrane integrity is not light dependent. Reversal of its effects on root growth was obtained with treatment by various amino acids, with histidine and glycine providing ca. 40% reversion. The strong reversal effect obtained with reduced glutathione is due to cross-reactivity with DHZ and the formation of mono- and di-adducts. Photosynthetic, respiratory and mitotic processes, as well as NADH oxidase activity appear to be unaffected by this compound. Our results indicate that dehydrozaluzanin C exerts its effects on plants through two different mechanisms, only one of which is related to the disruption of plasma membrane function.

Distribution and concentration of total phenolics, condensed tannins, and nordihydroguaiaretic acid (NDGA) in creosotebush (Larrea tridentata)

This paper focuses on the presence and distribution of secondary phenolic compounds found within creosotebush [Larrea tridentata (Sess. & Moc. ex DC.) Cov.]. Total phenolics, condensed tannins and nordihydroguaiaretic acid (NDGA) were measured in nine categories of tissue within creosotebush. Total phenolic and condensed tannin concentrations were determined using colorimetric methods while NDGA content was determined with high performance liquid chromatography (HPLC). Phenolics were present throughout the plant with the highest concentrations in leaves (36.2 mg/g), green stems (40.8 mg/g) and roots (mean for all root categories=28.6 mg/g). Condensed tannins were found in all tissues with highest concentrations in flowers (1.7 mg/g), seeds (1.1 mg/g), and roots less than 5 mm in diameter (1.1 mg/g). Flowers, leaves, green stems and small woody stems (<5 mm in diameter) all contained NDGA with highest concentrations in leaves (38.3 mg/g) and green stems (32.5 mg/g).This is the first report we are aware of giving secondary chemical characteristics of creosotebush roots. Data reported here will be used to support further research into the dynamics of shrub replacement and dominance of arid grasslands.

Extracts of Flourensia cernua (L): volatile constituents and antifungal, antialgal, and antitermite bioactivities.

The chemical components of tarbush (Flourensia cernua) leaves were fractionated by extracting successively with hexanes, diethyl ether, and ethanol. Volatile profiles of each fraction were identified by using GC-MS. The hexanes fraction contained mostly monoterpenoids, while the ethanol fraction volatiles were primarily sesquiterpenoids. Crude fractions were tested for activity against fungi, algae, and termites. Application of as little as 1 μg of the essential oil from the hexanes fraction was sufficient to provide visible antifungal activity in bioautography assays. The diethyl ether fraction showed selective activity against the cyanobacterium responsible for the 2-methylisoborneol-induced off-flavor sometimes associated with catfish farming operations. All three fractions exhibited a high degree of antitermite activity.

Composition of the essential oil of Lepidium meyenii (Walp).

The essential oil profile of maca (Lepidium meyenii) obtained from Lima, Peru, was examined. Steam distillates of the aerial parts of L. meyenii were continuously extracted with pentane and the pentane extracts analyzed by GC/MS. Retention indices and mass spectral data were used to identify 53 oil components. Phenyl acetonitrile (85.9%), benzaldehyde (3.1%), and 3-methoxyphenylacetonitrile (2.1%) were the major components of the steam distilled oil. The oil of L. meyenii was tested for phytotoxic, cyanobactericidal, and antitermite activity. The oil was selectively toxic towards the cyanobacterium Oscillatoria perornata compared to the green alga Selenastrum capricornutum, with complete growth inhibition at 100 microg/ml. Mortality of the Formosan subterranean termite, Coptotermes formosanus, was numerically, but not significantly, higher when held on filter paper treated with maca oil. At 1% (w/w), maca oil also appeared to act as a feeding deterrent to termites. Several minor components of the essential oil of maca including 3-methoxyphenylacetonitrile and benzylthiocyanate were significantly active against the Formosan termite. This is the first report on the essential oil composition of L. meyenii.

Phytotoxicity and volatile constituents from leaves of Callicarpa japonica Thunb.

The essential oil from the leaves of Callicarpa japonica was analyzed by GC-MS, and 84 compounds were identified. The main constituents of the essential oil were spathulenol (18.1%), germacrene B (13.0%), bicyclogermacrene (11.0%), globulol (3.3%), viridiflorol (2.6%), alpha-guaiene (2.3%), and gamma-elemene (2.0%). The essential oil constituents of C. japonica were significantly different from those found in our previous work on Callicarpa americana. The oil of C. japonica was selectively phytotoxic to bentgrass compared to lettuce seeds, with 80-100% growth reduction observed at 0.3 mg/ml.

Essential Oil of Flourensia cernua DC.

Abstract The leaf oil of Flourensia cernua DC. collected from the Jomada Experimental Range in southcentral New Mexico was analyzed. GC/MS and retention indices were used to identify 89 components. β-Eudesmol (24.5%), α-eudesmol (6.9%), limonene (6.6%), γ-eudesmol (4.6%), myrcene (3.8%), borneol (3.3%), and δ-3-carene (3.0%) were the major components of the steam distilled oil. In an ethanol extract of intact leaves, flourensadiol (44.6%), artemisia alcohol (5.5%), viridiflorol (2.7%), and borneol (2.0%) were the main components.

Composition and phytotoxic activity of Nepeta pannonica L. essential oil

Abstract The chemical composition of the essential oil of the aerial part of Nepeta pannonica L. from Kazakhstan was investigated by GC and GC/MS. Sixty components were characterized from N. pannonica with 1,8-cineole (28.9%), and 4aa,7β,7aα-nepetalactone (14.3%) as the major constituents. The oil of N. pannonica was more phytotoxic to bentgrass compared to lettuce seeds, with 100% growth inhibition observed at 0.3, and 1.0 mg/mL, respectively.

Extracts of Flourensia cernua Reduce Consumption of Alfalfa Pellets by Sheep

Effects of three extracts (hexanes, ether, and ethanol) from tarbush (Flourensia cernua) on intake of alfalfa pellets by lambs were examined. Forty-five ewe lambs were fed one of five treatments for five days (randomized complete block, three lambs per block on each treatment). Treatments were alfalfa pellets (CON) or alfalfa pellets plus ethanol carrier (CAR), hexanes extract (HEX), ether extract (ETH), or ethanol extract (ETOH). Extracts were applied to alfalfa pellets at the same concentration as in an equivalent amount of tarbush (as fed basis) in experiment 1 and at 10-fold dilutions of that concentration in experiment 2. Treatments were isolated from tarbush leaves by using a sequential extraction with hexanes, diethyl ether, and 100% ethanol. Lambs received 640 g of alfalfa pellets (dry matter basis) each morning and intake was monitored during a 20-min interval. Lambs were maintained and fed alfalfa pellets (4.7% of body weight) as one group except during this interval. In experiment 1, mean intake by lambs during the 20-min interval was 361, 393, 204, 212, and 228 g for CON, CAR, HEX, ETH, and ETOH, respectively (SEM = 28.9). All three extracts decreased intake (P < 0.001) compared to CON or CAR. Intake did not differ among the three extracts (HEX, ETH, and ETOH) or between the two controls (CON and CAR). Mean intake did not differ among treatments in experiment 2 (468, 455, 389, 381, and 431 g for CON, CAR, HEX, ETH, and ETOH, respectively; SEM = 30.5; P = 0.187). Several compounds are probably responsible for the low palatability and differential use of tarbush typically exhibited by livestock.