“Azadirachtin”的意思、由来-开放百科全书

Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen-bearing functional groups, including an enol ether, acetal, hemiacetal, tetra-substituted epoxide and a variety of carboxylic esters.

Chemical synthesis

Azadirachtin has a complex molecular structure; it presents both secondary and tertiary hydroxyl groups and a tetrahydrofuran ether in its molecular structure, alongside 16 stereogenic centres, 7 of which are tetrasubstituted. These characteristics explain the great difficulty encountered when trying to prepare this compound from simple precursors, using methods of synthetic organic chemistry.

Hence, the first total synthesis was published over 22 years after the compound's discovery: this first synthesis was completed by the research group of Steven Ley at the University of Cambridge in 2007.^[1]^[2] The described synthesis was a relay approach, with the required, heavily functionalized decalin intermediate being made by total synthesis on a small scale, but being derived from the natural product itself for the gram-scale operations required to complete the synthesis.

Occurrence and use

Initially found to be active as a feeding inhibitor towards the desert locust (Schistocerca gregaria),^[3] it is now known to affect over 200 species of insects, by acting mainly as an antifeedant and growth disruptor. It was recently found that azadirachitin possesses considerable toxicity towards African cotton leafworm (Spodoptera littarolis), which are resistant to a commonly used biological pesticide, Bacillus thuringiensis. Azadirachtin fulfills many of the criteria needed for a good insecticide. Azadirachtin is biodegradable (it degrades within 100 hours when exposed to light and water) and shows very low toxicity to mammals (the {{LD50}} in rats is > 3,540 mg/kg making it practically non-toxic).

This compound is found in the seeds (0.2 to 0.8 percent by weight) of the neem tree, Azadirachta indica (hence the prefix aza does not imply an aza compound, but refers to the scientific species name). Many more compounds, related to azadirachtin, are present in the seeds as well as in the leaves and the bark of the neem tree which also show strong biological activities among various pest insects ^[4]^[5] Effects of these preparations on beneficial arthropods are generally considered to be minimal. Some laboratory and field studies have found neem extracts to be compatible with biological control. Because pure neem oil contains other insecticidal and fungicidal compounds in addition to azadirachtin, it is generally mixed at a rate of 1 ounce per gallon (7.8 ml/l) of water when used as a pesticide.

Azadirachtin is the active ingredient in many pesticides including TreeAzin,^[6] AzaMax,^[7] BioNEEM,^[8] AzaGuard,^[9] and AzaSol^[10], Terramera Proof ^[11] and Terramera Cirkil ^[12].

Azadirachtin has a synergistic effect with the biocontrol agent Beauveria.^[13]

Biosynthesis

Azadirachtin is formed via an elaborate biosynthetic pathway, but is believed that the steroid tirucallol is the precursor to the neem triterpenoid secondary metabolites. Tirucallol is formed from two units of farnesyl diphosphate (FPP) to form a C₃₀ triterpene, but then loses three methyl groups to become a C₂₇ steroid. Tirucallol undergoes an allylic isomerization to form butyrospermol, which is then oxidized. The oxidized butyrospermol subsequently rearranges via a Wagner-Meerwein 1,2-methyl shift to form apotirucallol.

Apotirucallol becomes a tetranortriterpenoid when the four terminal carbons from the side chain are cleaved off. The remaining carbons on the side chain cyclize to form a furan ring and the molecule is oxidized further to form azadirone and azadiradione. The third ring is then opened and oxidized to form the C-seco-limonoids such as nimbin, nimbidinin and salannin, which has been esterified with a molecule of tiglic acid, which is derived from L-isoleucine. It is currently proposed that the target molecule is arrived at by biosynthetically converting azadirone into salanin, which is then heavily oxidized and cyclized to reach azadirachtin.

See also

References

1. ^{{cite journal |vauthors=Veitch GE, Beckmann E, Burke BJ, Boyer A, Maslen SL, Ley SV | title = Synthesis of azadirachtin: a long but successful journey | journal = Angew. Chem. Int. Ed. Engl. | volume = 46 | issue = 40 | pages = 7629–32 | year = 2007 | pmid = 17665403 | doi = 10.1002/anie.200703027 | url = }}
2. ^{{cite journal | author = Sanderson K | title = Chemists synthesize a natural-born killer | journal = Nature | volume = 448 | issue = 7154 | pages = 630–1 |date=August 2007 | pmid = 17687288 | doi = 10.1038/448630a }}
3. ^{{cite journal | title = Isolation of a Substance that suppresses Feeding in Locusts | last1 = Butterworth | first1 = J | last2 = Morgan | first2 = E | journal = Chemical Communications (London) | year = 1968 | issue = 1 | pages = 23 | doi = 10.1039/C19680000023 }}
4. ^{{cite journal | author = Senthil-Nathan, S. | author2 = Kalaivani, K. | author3 = Murugan, K. | author4 = Chung, G. | year = 2005 | title = The toxicity and physiological effect of neem limonoids on Cnaphalocrocis medinalis (Guenée) the rice leaffolder | doi = 10.1016/j.pestbp.2004.10.004 | journal = Pesticide Biochemistry and Physiology | volume = 81 | issue = 2 | pages = 113}}
5. ^{{cite journal | author = Senthil-Nathan, S. | author2 = Kalaivani, K. | author3 = Murugan, K. | author4 = Chung, P.G. | year = 2005 | title = Effects of neem limonoids on malarial vector Anopheles stephensi Liston (Diptera: Culicidae) | doi = 10.1016/j.actatropica.2005.07.002 | journal = Acta Tropica | volume = 96 | pages = 47–55 | pmid = 16112073 | issue = 1}}
6. ^{{cite web |url=http://www.bioforest.ca/index.cfm?fuseaction=content&menuid=12&pageid=1012 |title=TreeAzin Systemic Insecticide |publisher=BioForest Technologies |accessdate=2014-06-03}}
7. ^{{cite web |url=http://www.parryamerica.com/our-productsp2.html |title=Our Products |publisher=ParryAmerica, Inc. |accessdate=2015-02-18}}
8. ^{{Cite web|url=http://www.saferbrand.com/safer-brand-bioneem-insecticide-with-neem-oil-concentrate-16-oz-5612|title=Insecticide With Neem Oil Concentrate 16oz {{!}} Safer® Brand 5612|website=www.saferbrand.com|access-date=2016-09-28}}
9. ^{{cite web |url=http://www.biosafesystems.com/assets/azaguard-specimen.pdf |title=AzaGuard Botanical Insecticide Nematacide Specimen Label |publisher=Biosafe Systems, LLC |accessdate=2015-02-18}}
10. ^{{Cite web|url=http://arborjet.com/product/azasol/|title=AzaSol – Arborjet|website=arborjet.com|language=en-US|access-date=2017-06-16}}
11. ^{{Cite web|url=https://www.terramera.com/products/|title=Terramera – Proof|website=terramera.com|language=en-US|access-date=2018-09-20}}
12. ^{{Cite web|url=https://www.terramera.com/products/|title=Terramera – Cirkil|website=terramera.com|language=en-US|access-date=2018-09-20}}
13. ^Vyas, R. V., et al. (1992). [https://www.ncbi.nlm.nih.gov/pubmed/1459622 Effect of some natural pesticides on entomogenous muscardine fungi.] Indian J Exp Biol. 30(5) 435-6.

词条	Azadirachtin
释义	Chemical synthesis Occurrence and use Biosynthesis See also References External links {{chembox \| Watchedfields = changed \| verifiedrevid = 443410207 \| ImageFile = Azadirachtin.png \| ImageSize = 200px \|ImageFile1 = Azadirachtin_model.png \| ImageSize1 = 200px \| IUPACName = Dimethyl (2aR,3S,4S,R,S,7aS,8S,10R,10aS,10bR)-10-(acetyloxy)-3,5-dihydroxy-4-[(1S,2S,6S,8S,9R,11S)-2-hydroxy-11-methyl-5,7,10-trioxatetracyclo[6.3.1.0^2,6.0^9,11]dodec-3-en-9-yl]-4-methyl-8-{[(2E)-2-methylbut-2-enoyl]oxy}octahydro-1H-furo[3',4':4,4a]naphtho[1,8-bc]furan-5,10a(8H)-dicarboxylate \| OtherNames = Dimethyl (2aR,3S,4S,4aR,5S,7aS,8S,10R,10aS,10bR)-10-acetoxy-3,5-dihydroxy-4-[(1aR,S,3aS,6aS,7S,7aS)-6a-hydroxy-7a-methyl-3a,6a,7,7a-tetrahydro-2,7-methanofuro[2,3-b]oxireno[e]oxepin- 1a(2H)-yl]-4-methyl-8-{[(2E)-2-methylbut-2-enoyl]oxy}octahydro-1H-naphtho[1,8a-c:4,5-b'c']difuran-5,10a(8H)-dicarboxylate \| Section1 = {{Chembox Identifiers \| CASNo_Ref = {{cascite\|correct\|CAS}} \| CASNo = 11141-17-6 \| PubChem = 5281303 \| ChemSpiderID_Ref = {{chemspidercite\|correct\|chemspider}} \| ChemSpiderID = 4444685 \| KEGG_Ref = {{keggcite\|correct\|kegg}} \| KEGG = C08748 \| ChEBI_Ref = {{ebicite\|correct\|EBI}} \| ChEBI = 2942 \| SMILES = O=C(OC)[C@@]1(O)OC[C@]82[C@@H](OC(=O)/C(=C/C)C)C[C@@H](OC(=O)C)[C@@]7(C(=O)OC)CO[C@@H]([C@@H](O)[C@](C)([C@H]12)[C@]64O[C@]6([C@@H]3[C@@]5(O)/C=C\\O[C@H]5O[C@H]4C3)C)[C@@H]78 \| StdInChI_Ref = {{stdinchicite\|correct\|chemspider}} \| StdInChI=1S/C35H44O16/c1-8-15(2)24(38)49-18-12-19(48-16(3)36)32(26(39)43-6)13-46-21-22(32)31(18)14-47-34(42,27(40)44-7)25(31)29(4,23(21)37)35-20-11-17(30(35,5)51-35)33(41)9-10-45-28(33)50-20/h8-10,17-23,25,28,37,41-42H,11-14H2,1-7H3/b15-8+/t17-,18+,19-,20+,21-,22-,23-,25+,28+,29-,30+,31+,32+,33+,34+,35+/m1/s1 \| StdInChIKey_Ref = {{stdinchicite\|correct\|chemspider}} \| StdInChIKey = FTNJWQUOZFUQQJ-NDAWSKJSSA-N \| Section2 = {{Chembox Properties \| C=35\|H=44\|O=16 \| Appearance = \| Density = \| MeltingPt = \| BoilingPt = \| Solubility = \| Section3 = {{Chembox Hazards \| MainHazards = \| FlashPt = \| AutoignitionPt = }} Azadirachtin, a chemical compound belonging to the limonoid group, is a secondary metabolite present in neem seeds. It is a highly oxidized tetranortriterpenoid which boasts a plethora of oxygen-bearing functional groups, including an enol ether, acetal, hemiacetal, tetra-substituted epoxide and a variety of carboxylic esters. Chemical synthesis Azadirachtin has a complex molecular structure; it presents both secondary and tertiary hydroxyl groups and a tetrahydrofuran ether in its molecular structure, alongside 16 stereogenic centres, 7 of which are tetrasubstituted. These characteristics explain the great difficulty encountered when trying to prepare this compound from simple precursors, using methods of synthetic organic chemistry. Hence, the first total synthesis was published over 22 years after the compound's discovery: this first synthesis was completed by the research group of Steven Ley at the University of Cambridge in 2007.^[1]^[2] The described synthesis was a relay approach, with the required, heavily functionalized decalin intermediate being made by total synthesis on a small scale, but being derived from the natural product itself for the gram-scale operations required to complete the synthesis. Occurrence and use Initially found to be active as a feeding inhibitor towards the desert locust (Schistocerca gregaria),^[3] it is now known to affect over 200 species of insects, by acting mainly as an antifeedant and growth disruptor. It was recently found that azadirachitin possesses considerable toxicity towards African cotton leafworm (Spodoptera littarolis), which are resistant to a commonly used biological pesticide, Bacillus thuringiensis. Azadirachtin fulfills many of the criteria needed for a good insecticide. Azadirachtin is biodegradable (it degrades within 100 hours when exposed to light and water) and shows very low toxicity to mammals (the {{LD50}} in rats is > 3,540 mg/kg making it practically non-toxic). This compound is found in the seeds (0.2 to 0.8 percent by weight) of the neem tree, Azadirachta indica (hence the prefix aza does not imply an aza compound, but refers to the scientific species name). Many more compounds, related to azadirachtin, are present in the seeds as well as in the leaves and the bark of the neem tree which also show strong biological activities among various pest insects ^[4]^[5] Effects of these preparations on beneficial arthropods are generally considered to be minimal. Some laboratory and field studies have found neem extracts to be compatible with biological control. Because pure neem oil contains other insecticidal and fungicidal compounds in addition to azadirachtin, it is generally mixed at a rate of 1 ounce per gallon (7.8 ml/l) of water when used as a pesticide. Azadirachtin is the active ingredient in many pesticides including TreeAzin,^[6] AzaMax,^[7] BioNEEM,^[8] AzaGuard,^[9] and AzaSol^[10], Terramera Proof ^[11] and Terramera Cirkil ^[12]. Azadirachtin has a synergistic effect with the biocontrol agent Beauveria.^[13] Biosynthesis Azadirachtin is formed via an elaborate biosynthetic pathway, but is believed that the steroid tirucallol is the precursor to the neem triterpenoid secondary metabolites. Tirucallol is formed from two units of farnesyl diphosphate (FPP) to form a C₃₀ triterpene, but then loses three methyl groups to become a C₂₇ steroid. Tirucallol undergoes an allylic isomerization to form butyrospermol, which is then oxidized. The oxidized butyrospermol subsequently rearranges via a Wagner-Meerwein 1,2-methyl shift to form apotirucallol. Apotirucallol becomes a tetranortriterpenoid when the four terminal carbons from the side chain are cleaved off. The remaining carbons on the side chain cyclize to form a furan ring and the molecule is oxidized further to form azadirone and azadiradione. The third ring is then opened and oxidized to form the C-seco-limonoids such as nimbin, nimbidinin and salannin, which has been esterified with a molecule of tiglic acid, which is derived from L-isoleucine. It is currently proposed that the target molecule is arrived at by biosynthetically converting azadirone into salanin, which is then heavily oxidized and cyclized to reach azadirachtin. See also Arid Forest Research Institute (AFRI) Neem Neem cake Neem oil Nimbin, another chemical isolated from Azadirachta indica also thought to contribute to the biological activity of neem References 1. ^{{cite journal \|vauthors=Veitch GE, Beckmann E, Burke BJ, Boyer A, Maslen SL, Ley SV \| title = Synthesis of azadirachtin: a long but successful journey \| journal = Angew. Chem. Int. Ed. Engl. \| volume = 46 \| issue = 40 \| pages = 7629–32 \| year = 2007 \| pmid = 17665403 \| doi = 10.1002/anie.200703027 \| url = }} 2. ^{{cite journal \| author = Sanderson K \| title = Chemists synthesize a natural-born killer \| journal = Nature \| volume = 448 \| issue = 7154 \| pages = 630–1 \|date=August 2007 \| pmid = 17687288 \| doi = 10.1038/448630a }} 3. ^{{cite journal \| title = Isolation of a Substance that suppresses Feeding in Locusts \| last1 = Butterworth \| first1 = J \| last2 = Morgan \| first2 = E \| journal = Chemical Communications (London) \| year = 1968 \| issue = 1 \| pages = 23 \| doi = 10.1039/C19680000023 }} 4. ^{{cite journal \| author = Senthil-Nathan, S. \| author2 = Kalaivani, K. \| author3 = Murugan, K. \| author4 = Chung, G. \| year = 2005 \| title = The toxicity and physiological effect of neem limonoids on Cnaphalocrocis medinalis (Guenée) the rice leaffolder \| doi = 10.1016/j.pestbp.2004.10.004 \| journal = Pesticide Biochemistry and Physiology \| volume = 81 \| issue = 2 \| pages = 113}} 5. ^{{cite journal \| author = Senthil-Nathan, S. \| author2 = Kalaivani, K. \| author3 = Murugan, K. \| author4 = Chung, P.G. \| year = 2005 \| title = Effects of neem limonoids on malarial vector Anopheles stephensi Liston (Diptera: Culicidae) \| doi = 10.1016/j.actatropica.2005.07.002 \| journal = Acta Tropica \| volume = 96 \| pages = 47–55 \| pmid = 16112073 \| issue = 1}} 6. ^{{cite web \|url=http://www.bioforest.ca/index.cfm?fuseaction=content&menuid=12&pageid=1012 \|title=TreeAzin Systemic Insecticide \|publisher=BioForest Technologies \|accessdate=2014-06-03}} 7. ^{{cite web \|url=http://www.parryamerica.com/our-productsp2.html \|title=Our Products \|publisher=ParryAmerica, Inc. \|accessdate=2015-02-18}} 8. ^{{Cite web\|url=http://www.saferbrand.com/safer-brand-bioneem-insecticide-with-neem-oil-concentrate-16-oz-5612\|title=Insecticide With Neem Oil Concentrate 16oz {{!}} Safer® Brand 5612\|website=www.saferbrand.com\|access-date=2016-09-28}} 9. ^{{cite web \|url=http://www.biosafesystems.com/assets/azaguard-specimen.pdf \|title=AzaGuard Botanical Insecticide Nematacide Specimen Label \|publisher=Biosafe Systems, LLC \|accessdate=2015-02-18}} 10. ^{{Cite web\|url=http://arborjet.com/product/azasol/\|title=AzaSol – Arborjet\|website=arborjet.com\|language=en-US\|access-date=2017-06-16}} 11. ^{{Cite web\|url=https://www.terramera.com/products/\|title=Terramera – Proof\|website=terramera.com\|language=en-US\|access-date=2018-09-20}} 12. ^{{Cite web\|url=https://www.terramera.com/products/\|title=Terramera – Cirkil\|website=terramera.com\|language=en-US\|access-date=2018-09-20}} 13. ^Vyas, R. V., et al. (1992). [https://www.ncbi.nlm.nih.gov/pubmed/1459622 Effect of some natural pesticides on entomogenous muscardine fungi.] Indian J Exp Biol. 30(5) 435-6. External links Extoxnet Neem: The wonder tree 9 : Plant toxin insecticides\|Terpenes and terpenoids\|Acetate esters\|Epoxides\|Alcohols\|Carboxylate esters\|Methyl esters\|Alkenes\|Oxygen heterocycles
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Chemical synthesis

Occurrence and use

Biosynthesis

See also

References

External links