Neem

Contraction in the number of EPA-allowed biocides has heightened efforts to develop naturally derived preservatives and microorganisms capable of countering microbial degradation. Neem oil A. dirachta indica seed extract) has been featured as an exceptional natural candidate for the preservation of cosmetic products. Naturally derived chemicals with antimicrobial properties have been used since antiquity as preservatives. However, displacement of successhil synthetic products by natural products in preservatives of any category remains to be witnessed. 

Melia azadirachta L. (neem or margosa). The bark, according to Cornish, yields a minute amount of a bitter alkaloid, margosine. The fruit is reported to be toxic and to contain an alkaloid, azaridine. The leaves are stated to be insect-repellent and from them an alkaloid paraisine has been prepared. The flowers are alkaloid-free. ((1) Ind. Ann. Med. Sci., 1857, 4, 104 (2) Carratala, Rev. Asoc. med. Arg., 1939, 53, 338 (3) Volkonsky, Arch. Inst. Pasteur Alg rie, 1937, 427 (4) Subramanian and Rangaswamy, Curr. Sci., 1947, 16, 182.)... 

Shanker et al. [120] prepared bimetallic Au-core/ Ag-shell nanoparticles by the simultaneous reduction of Au(III) and Ag(I) ions in the presence of neem (Azadirachta indica) leaf broth as an extracting agent. 

Competitive reduction of Au(III) and Ag(I) ions occurs simultaneously in solution during exposure to neem leaf extract leads to the preparation of bimetallic Au-core/Ag-shell nanoparticles in solution. TEM revealed that the silver nanoparticles are adsorbed onto the gold nanoparticles, forming a core/sheU structure. Panigrahi et al. [121] reported that sugar-assisted stable Au-core/Ag-shell nanoparticles with particles size of ca. 10 nm were prepared by a wet chemical method. Fructose was found to be the best suited sugar for the preparation of smallest particles. 

Preservatives which are based on natural ingredients or nature identical are small in numbers and these are gaining the attention of marketers. The ones I am aware of are - Grapefruit Seed extracts and Usnic Acid distributed by Paroxite, Neem seed oil... 

Azadirachtin (Neem) Aza-direct, Neemix Whitefly, caterpillars, leafminer, aphid, DBmoth Various fruits and vegetables Insecticide... 

Arivazhagan S, Velmurugan B, Bhuvaneswari V and Nagini S. 2004. Effects of aqueous extracts of garlic (Allium sativum) and neem (Azadirachta indica) leaf on hepatic and blood oxidant-antioxidant status during experimental gastric carcinogenesis. J Med Food 7(3) 334—339. 

Krishnayya PV, Grewal PS. Effect of neem and selected fungicides on viability and virulence of the entomopathogenic nematode Steinemema feltiae. Biocont Sci Tech. 2002 12 259-266. 

On the other hand, the assumption that substances permitted as natural pesticides by the organic farming standards are harmless to non-target animals and humans still has to be proven. An urgent call for further investigation exists as recent studies of Neem (Azadirachta indicd) extracts, for example, demonstrated their harmful potential by affecting abortion pregnancy of rats, baboons and monkeys (Talwar et al. 1997). 

Talwar, G. P., Shaha, S., Mukherehee, S. and R. Chabra (1997). Indueed Termination of Pregnancy by Purified Extracts of Azadirachta Indica (Neem) -Mechanisms Involved. American Journal of Reproductive Immunology 37 (6) 485-491. 

Ganguli S. (2002) Neem A therapeutic for all seasons. Current Science 82 1304. 

Brahmachri G. (2004) Neem-an omnipotent plant A retrospection. Chem Bio Chem 5 408 21. 

Birds that breed in cavities and reuse their nest sites often incorporate green parts of aromatic plants into their nests. Starlings, Sturnus vulgaris, prefer certain species of plants to others. House sparrows. Passer domesticus, incorporate neem (margosa) tree, Azadirachta indica, leaves into their nests. Extracts from neem leaves repel arthropods and inhibit oviposition (Sengupta, 1981). The aromatic plants are thought to fulfill an important function by keeping down populations of microbes in the birds nests (Mason and Clark, 1986). 

The peer-reviewed literature is full of reports on natural products possessing insecticidal activity and references therein] therefore, the focus of this section will be on both recent and well investigated natural products. Of those well investigated natural products, at least three natural product derived products (neem, spinosyn, and pyrethrum) seem to be used more than all the others. 

The seeds from the Indian neem tree, Azadirachta indica, are the source of two types of neem-derived botanical insecticides neem oil and medium polarity extracts. Neem seeds contain numerous azadirachtin (Fig. 9) analogs, but the major form is azadirachtin and the remaining minor analogs are likely to contribute little to the overall efficacy of the extracts. Typically, solvent partitions or other chemical processes are required to concentrate this active ingredient to the level of 10% to 50% seen in the technical grade material used to produce commercial products. 

Table VII. Ecdysis-and Growth-Inhibitory Activities of Some Neem...

Another limonoid isolated from neem seeds and determined to be as potent as azadirachtin as an ecdysis inhibitor has been identified as 3-deacetylazadirachtinol (Figure 15) (57). Both compounds were lethal to 50% of the treated H. virescens larvae (EI5Q) at 0.8 ppm in artificial diet (Table VII). Structurally, there are two differences between the compounds. In 3-deacetylazadirachtinol, the C-ll-O-C-13 ether linkage of azadirachtin is reductively cleaved at the 11 position and the acetoxyl group at C-3 is hydrolyzed to a hydroxyl group. 

Jacobson, M. In "Natural Pesticides from the Neem Tree (Azadirachta Indica A. Juss.)" Schmutterer, H. Ascher, K.R.S. Rembold, H., Eds. German Agency for Technical Cooperation Eschborn, Germany, 1980 pp. 33-42,... 

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