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1.
To clarify the biosynthesis of syringyl lignans and lignan formation by stereoselective coupling of monolignols, formation of (+)-syringaresinol and (+)-pinoresinol inLiriodendron tulipifera were investigated by means of feeding experiments. Following individual administration ofl-[U-14C]phenylalanine and [8-14C]sinapyl alcohol to excised shoots ofL. tulipifera and their subsequent metabolism for 3h, free [14C] lignans and [14C] lignan glucosides were extracted from both of the stems and leaves with methanol and divided into an ether fraction and an aqueous one, respectively. The glucosides were hydrolyzed by a combination of cellulase and-glucosidase to liberate [14C]lignans as aglycones.l-[U-14C]Phenylalanine was incorporated into free (+)-[14C]syringaresinol and its glucosides; the (+)-[14C]syringaresinols in the stems and leaves had 52% enantiomeric excess (% e.e.) and 42% e.e., respectively; and the (+)-[14C]syringaresinol aglycones from the glucosides in the stems and leaves had 20% e.e. and 22% e.e., respectively. Furthermore, [8-14C]sinapyl alcohol was incorporated into (+)-[14C]syringaresinol and its glucosides in the stems. These results suggest that the (+)-enantiomer of syringaresinol was enantioselectively formed from two molecules of sinapyl alcohol inL. tulipifera followed by transformation into the (+)-syringaresinol glucosides, accompanying the formation of racemic syringaresinol by nonselective coupling and the subsequent transformation of the racemate into their glucosides.l-[U-14C]Phenylalanine was incorporated also into free (+)-[14C]pinoresinol and its glucosides with 12%–42% e.e.Part of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society, Kochi, April 1997 相似文献
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Betulinic acid, isolated in substantial amounts from stem barks of five distinct species of Uapaca could be considered as an important chemotaxomic marker of the Uapaca genus. It inhibited Trypanosoma brucei GAPDH with an IC(50) value of 240 microM and has been shown to be a competitive reversible inhibitor (Ki=200+/-10 microM) of this enzyme with respect to its cofactor NAD(+). 相似文献
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运用双因素随机区组设计方案 ,研究了稀土、赤霉素 (GA3)和吲哚丁酸 (IBA)三种植物生长调节剂对三个锥栗品种无性系产量增加的影响。结果表明 :稀土微肥不同浓度喷施对产量有显著的影响 ,以 40 0 ppm (A1 )为最佳 ;两种生长调节剂中 ,则以 GA3的效果更好 (B1 ) ;AB因素两种组合的混合喷施对产量的促进有交互作用 ,各种组合中以A1 B1 ,即稀土浓度为 40 0 ppm ,GA3浓度为 5 0 ppm的交互效应对产量的提高最显著。 相似文献
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A. Krilov 《Wood Science and Technology》1976,10(3):199-208
Summary Examination of the bandsaw teeth (1) untreated, (2) swaged and (3) treated by thermal high-frequency surface hardening method has shown that their average microhardness is 473 DPN (<46 Rc), 502 DPN (<49 Rc) and 836 DPN (>62 Rc) respectively.Scanning electron microscopy revealed that no significant change occurred within the crystalline microstructure of untreated and swaged specimens. The high-frequency treated specimen, however, has shown a definite structural modification of a very finely grained martensitic type, extending from the apex for a distance of 0.24 mm.The relationship between DPN microhardness distribution throughout the bandsaw steel and the range of H.F. impulse times from 24/50 to 36/50 of a second was also investigated, and depth of the hardened zone determined.The optimal H.F. impulse time length corresponding to the optimal tooth hardness appears to lie between 32 and 33/50 of a second. Operating with 32/50 impulse time on a conventional 2.41 mm thick SANDVIK bandsaw with 0.73 mm side swage, it was found that the average hardness of a H.F. treated tooth apex is about 905 DPN (>64 Rc) to a depth of 415 m and in practical terms approaches the estimated optimum for high-speed cutting. 相似文献
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Dr. U. Skatulla 《Journal of pest science》1987,60(1):15-18
Gipsy moth-larvae from different geographical regions were infected with an NPV-virus. The susceptibility of the tested larvae populations to this virus was very different, this could be shown by the mortality and incubation-times (Lt50) of the observed populations. 相似文献
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Chris J. PengellyRalph V. Cartar 《Forest Ecology and Management》2011,261(11):2068-2074
The rate of floral nectar production, an important trait for supporting populations of pollinators, is known to be affected by local environment. This study examines the effect, 9 years after an anthropogenic disturbance—variable retention logging,—on the rate of daily nectar production of four common herbs (Chamerion angustifolium, Delphinium glaucum, Mertensia paniculata and Vicia americana) in the boreal forest of Alberta, Canada. We measured daily nectar production rates 9 years after experimental logging in three treatments: clear cuts (all merchantable trees removed), 50% of trees retained, and unlogged controls. Per-flower nectar production rate was unaffected by logging for C. angusifolium, D. glaucum, and M. paniculata, and lower in unlogged controls than in the 50% logging treatment for V. americana. Overall, we found a surprising robustness of nectar production of these herbaceous plants to the physical and environmental changes following logging. While other research has shown boreal forest logging to affect the densities of understory herbs, the per-flower nectar production in boreal forest understory herbs appears to be relatively insensitive to this disturbance. 相似文献
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《Forest Ecology and Management》1998,108(3):251-260
In East Kalimantan (Indonesia), impacts of conventional (CNV) and reduced-impact logging (RIL) on forest ecosystems were compared on the basis of pre- and post-harvesting stand inventories. There was a positive and significant correlation between the proportion of trees damaged by felling and the density of trees felled. Logging intensity ranged from 1 to 17 trees ha−1(9–247 m3 ha−1) and averaged 9 trees ha−1 (86.9 m3 ha−1). The study has shown that with RIL techniques, logging damage on the original stand can be significantly reduced by 50% compared with conventional logging. However, this 50% reduction in logging damage, was dependent on the felling intensity. With a felling intensity of 8 stems ha−1 or less, RIL techniques only damaged 25% of the original tree population whereas 48% were damaged with conventional techniques. Above this felling intensity (i.e. 8 stems ha−1), the effectiveness of RIL in limiting forest damage was significantly reduced, mainly because of the increasing felling damage. Moreover, the removal of all harvestable timber trees, leaving only few potential crop trees, will result in a seriously depleted residual stand. Because of the high damage involved by high felling intensity, leaving few potential crop trees, and the yield capacity of the remaining stand, acceptable harvesting volume will not be reached within the felling rotation of 35 years. It is concluded that silvicultural system based on diameter limit alone, as is the Indonesian system (TPTI), cannot be compatible with sustainability and more sophisticated harvested-selection rules are needed. 相似文献
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The essential oil of Artemisia annua aerial parts, consisting of camphor (44%), germacrene D (16%), trans-pinocarveol (11%), beta-selinene (9%), beta-caryophyllene (9%) and artemisia ketone (3%), was screened for its antimicrobial activity. The essential oil remarkably inhibited the growth of tested Gram-positive bacteria Enterococcus hirae and both tested fungi. This oil has shown an antioxidant activity equivalent to 18% of the reference compound (alpha-tocopherol). 相似文献
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MD. Atiar Rahman Takeshi Katayama Toshisada Suzuki Yuka Yoshihara Takashi Nakagawa 《Journal of Wood Science》2007,53(2):114-120
To clarify the biosynthetic pathway for syringyl lignans, especially syringyl tetrahydronaphthalene lignans and formation
of the C2–C7′ linkage, production of (+)-lyoniresinol (LYR) and its predicted intermediates [syringaresinol (SYR), 5,5′-dimethoxylariciresinol
(DMLR), and 5,5′-dimethoxysecoisolariciresinol (DMSLR)] in Lyonia ovalifolia var. elliptica was investigated by means of feeding experiments with radiolabeled precursors. Following individual administration of l-[U-14C]phenylalanine (Phe), [8-14C]sinapyl alcohol (SA), and [8,8′-14C]SYR to excised young shoots of L. ovalifolia and their subsequent metabolism, free [14C]lignans and [14C]lignan glycosides were extracted with methanol from stems and leaves and were divided into ethyl acetate-soluble fractions
(lignans) and aqueous fractions (lignan glycosides), respectively. Using a combination of xylanase, cellulase, and β-glucosidase, the glycosides were hydrolyzed to liberate [14C]lignans as aglycones. l-[U-14C]Phe was incorporated into (+)-[14C]SYR [stem 0.38%, 8% enantiomeric excess (e.e.)], (−)-[14C]SYR (leaves 2.75%, 72% e.e.), (+)-[14C]DMLR (stem 0.07%, 18% e.e. and leaves 0.009%, 58% e.e.), (−)-[14C]DMSLR (stem 0.03%, 46% e.e. and leaves 0.05%, 20% e.e.), (+)-[14C]LYR (leaves 0.013%, 22% e.e.) and glycosides of (+)-[14C]LYR (stem 0.036%, 50% e.e.) in 24h. Based on the percent incorporation and enantiomeric composition of the lignans, the
biosynthetic pathway of (8R,8′R)-(+)-LYR was proposed as follows: a nonselective dehydrogenative dimerization of sinapyl alcohol yields (±)-SYR, which is
reduced with low specificity to give (8R,8′R)-(+)-DMLR. This is cyclized to directly give (+)-LYR as well as reduced again to (8R,8′R)-(−)-DMSLR. Although further transformation of (−)-DMSLR also leads to the formation of (+)-LYR, cyclization could be a main
pathway for (+)-LYR biosynthesis.
This report was presented at the IAWPS 2005 International Symposium on Wood Science and Technology, Yokohama, November 2005 相似文献
11.
《Fitoterapia》2014
4-Hydroxyisoleucine (4-HIL) is an unusual amino acid isolated from fenugreek seeds (Trigonella foenum graecum L). Various studies have shown that it acts as an antidiabetic agent yet its mechanism of action is not clear. We therefore investigated the effect 4-HIL on the high fructose diet fed streptozotocin induced diabetic rats and L6 myotubes. 4-HIL (50 mg/kg) has improved blood lipid profile, glucose tolerance and insulin sensitivity in a diabetic rat model. It has increased the glucose uptake in L6 myotubes in AMPK-dependent manner and upregulated the expression of genes (PGC-1α, PGC-1β, CPT 1 and CPT 2), which have role in mitochondrial biogenesis and energy metabolism in the liver, skeletal muscles as well as in L6 myotubes. Interestingly, it also increased the AMPK and Akt expression along with their phosphorylated forms in the liver and muscle tissues of treated animals. Altogether we concluded that 4-HIL acts to improve insulin resistance by promoting mitochondrial biogenesis in high fructose diet fed STZ induced diabetic rats. 相似文献
12.
Recent studies have shown biological effects of heme oxygenase-1 (HO-1) induction and antioxidation in cardiovascular disorders. The ethanol extracts of leaves of 12 selected indigenous Taiwanese plants were investigated for their antioxidant activities, evaluated using assays of 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, and superoxide radicals scavenging and reducing power activities as well as the induction of heme oxygenase-1 (HO-1). Acer albopurpurascens, Cinnamomum kanehirai, Diospyros discolor, Excoecaria kawakamii, Koelreuteria henryi, and Syzygium formosanum showed better DPPH-scavenging activities than the other plants. IC(50) values ranged from 1.7 to 8.7 microg/mL. Excepting Millettia pulchra var. microphylla and Pittosporum moluccanum, the extracts displayed hydroxyl-scavenging activities (IC(50) of 0.16-0.67 microg/mL). A. albopurpurascens, D. discolor, K. henryi, and S. formosanum also showed good superoxide anion radical scavenging activities and IC(50) values ranged from 12.9 to 28.5 microg/mL. D. discolor, K. henryi, and S. formosanum showed potent reducing power and M. pulchra var. microphylla and S. formosanum exhibited potent HO-1 induced activity. These active plant extracts also contained abundant phenolic constituents. The present results provide candidates to isolate the active constituents and develop natural antioxidants. 相似文献
13.
In the search for new sources of sesquiterpene lactones, six Centaurea species have been analyzed. The activity against the fungus Cunninghamella echinulata of (+)-cnicin (1) and (+)-salonitenolide (2), isolated from the Centaurea plants, as well as that of (+)-costunolide (3), (-)-dehydrocostuslactone (4), (-)-lychnopholide (5) and (-)-eremantholide C (6), has been evaluated. Compounds 3 and 4 showed noticeable EC50 values, whilst more polar lactones were inactive. These results suggest that a relatively low polarity is one of the molecular requirements for the antifungal activity of sesquiterpene lactones. 相似文献
14.
提高昆虫病毒杀虫效果的荧光增白剂的研究 总被引：10，自引：0，他引：10
荧光增白剂是生物防治研究中最近发现的一类能显著提高昆虫病毒杀虫能力、加快病毒致死昆虫速度、提高昆虫病毒对紫外光的保护作用的化学因子。林间增加效果明显而稳定。荧光增白剂可发展成为有效提高和改善昆虫病毒制剂持续控制农林害虫的重要助剂。虽然荧光增白剂能显著增强昆虫病毒毒力的机理还不清楚，但该机理的阐明可以为生物防治农林害虫提供新的途径甚至理论。本文综述了近10a来国外在应用荧光增白剂提高昆虫病毒毒力和实际应用防治农林害虫的研究进展。并提出了荧光增白剂能扩大病毒的宿主范围，改变昆虫病毒感染宿主的途径和诱发昆虫病毒潜伏侵染的推论。对荧光增白剂应用中的问题也进行了讨论。 相似文献
15.
Lipoxygenase (LOX)-inhibiting compounds from the leaves of Chisocheton polyandrus Merr. were isolated in this study using a bioactivity-guided fractionation technique. Two dammarane triterpenoids, dammara-20,24-dien-3-one (1) (IC(50)=0.69±0.07 μM) and 24-hydroxydammara-20,25-dien-3-one (2) (IC(50)=1.11±0.38 μM), were isolated and identified based on the soybean LOX assay. Dammara-20,24-dien-3-one (1) exhibited dual inhibition of both human 5-LOX (IC(50)=24.27±2.92 μM) and cyclooxygenase-2 (COX-2) (IC(50)=3.17±0.90 μM), whereas 24-hydroxydammara-20,25-dien-3-one (2) did not exhibit any significant inhibitory effects. This report is the first to detail the inhibition of LOX and COX by both C. polyandrus and its isolated compounds. 相似文献
16.
植物生长调节剂处理对梨矮化砧木SPRB15快速成苗影响的研究 总被引：1，自引：0，他引：1
为了确立梨矮化砧木快速成苗技术,采用不同植物生长调节剂处理,研究了植物生长调节剂对梨矮化性砧木SPRB15快速成苗的影响。结果表明:间隔7天连续2次喷布GA4 7100 mg/L的处理4的地径生长量、苗高生长量均为最大,是本试验中的最佳处理。其次是2次喷布GA3100 mg/L的处理2,依次为2次喷布GA4 750 mg/L的处理3,2次喷布GA350 mg/L的处理1,2次喷布BA 250 mg/L的处理5。据此结果认为:GA4 7和GA3对于梨矮化性砧木SPRB15幼苗苗木的生长具有显著的促进效果;BA对于梨矮化砧木SPRB15苗木侧芽的萌发具有显著的促进效果。 相似文献
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《林业研究》2021,32(3)
Tropical forest cover change along with increasing fragmentation has detrimental effects on the global biodiversity. In the current study change in both forest cover and fragmentation of Koraput district have been assessed in the past three decades(1987-2017) and future decade(2017-2027), which has been modelled using logistic regression showing a gradual decrease in the forest cover and increase in fragmentation. The long term deforestation rates from 1987 to 2017(current period) and from 1987 to 2027(predicted period) were found to be-0.018 and-0.012, respectively. Out of the total geographical area, 2027 number of grids(1 km2) out of 8856 grids were found to have shown extinction of forest in the study period. The conversion of forested lands into other land uses has been one of the major causes of deforestation in Koraput, especially because of the increasing mining activities and establishment of three major industries namely National Aluminium Company(NALCO), Damanjodi, Hindustan Aeronautics Limited(HAL), Sunabeda and Ballarpur Industries Limited(BILT). The forest fragmentation reveals a negative trend, recording highest conversion from large core fragments to edge(191.33 km2) and the predicted period has also shown the same trend of negative change, which poses serious danger to the structure of the forests. Out of all the landscape matrices calculated, number of patches will increase to 214 in 2027 from 93 in 1987. In the test between geographically weighted regression(GWR) and ordinary least square regression(OLS), GWR was the better fit model for drawing a spatial relationship between forest cover and fragmentation changes. The study confirmed that the forest cover change has impacted the forest fragmentation in the study area. The programmes like REDD + should be implemented along with the experiences of Community Forest Management and the joint forest management should be intensified at community level in order to develop better management practices to conserve habitats in biodiversity rich areas. 相似文献