Plants juglone from

When tomato and alfalfa plants were planted different distances from walnut trees, plants close to the tree did not survive. The position at which the tomato plants were unaffected by the allelopathy coincided with the extent of the root growth of the tree and it was assumed that the plants were killed by the exudation of toxin from the roots. Later work suggested that the effect might actually be caused by leaching of a bound form of juglone from the leaves and stems followed by hydrolysis and oxidation in the soil to release the actual... 

It seems unlikely that the allelopathic chemicals that may be extracted from plant material are actually those that reach the host plant, yet nearly all our information on allelopathic compounds is derived from extracts that have never been exposed to the soil. Some compounds, such as juglone, may remain unchanged in the soil under some circumstances ( ), but many compounds, such as ferulic or salicylic acid, are converted to other chemicals in the soil. 

The higher juglone concentrations in the surface soil and within a few centimeters of the soil surface beneath the walnut was due to the presence of leaves, fruit, and roots. Juglone concentrations in this bottomland plantation followed a pattern similar to treatment differences reported for a companion upland mixed planting (26). However, results from the present Investigation showed juglone... 

The biosynthesis of these anthraquinones parallels those of the menoquinones in bacteria and naphtoquinones of plants for example juglone, vitamin K and lawsone. These compounds are also derived from shikimic (or chorismic) and a-ketoglutaric acids via o-succinylbenzoic acid [5,24]. 1,4-Dihydroxy-2-naphtoic acid is the branching point in the biosynthesis of menoquinones, naphtoquinones and anthraquinones [4],... 

The naturally occurring naphthoquinones such as lawsone and juglone are products of the shikimic acid pathway to aromatic amino-acids but the path which leads to these naphthoquinones branches from the main pathway before the formation of aromatic compounds, probably no later than chorismic acid.It will be most interesting to see whether the biosynthesis of shihunine also follows this route all the other bases of plant origin which arise from products of the shikimic acid pathway derive from aromatic precursors. 

Juglone, a dye known for centuries, is produced from the husks of hlack walnuts. It is also a natural herbicide (weed killer) that kills off competitive plants around the black walnut tree but does not affect grass and other noncompetitive plants. The formula for juglone is C QHg03. 

Naphthoquinones naturally occurring derivatives of 1,4-naphthoquinone. N. are widely distributed, and over 120 different N. are known in higher plants, bacteria and fungi. Examples of N. from plants are alkan-nin, eleutherin, juglone, lapachol, lawsone, lomatiol plumbagin and shikonin. In the animal kingdom, N. 

Until recently it was believed that chorismic acid is the branch point compound that links the shikimate pathway to the vitamin K biosynthetic pathway. "" Recent results show that this is not true (vide infra). Since vitamin K was assumed to be derived from chorismic acid, it was concluded that plant quinones which, like vitamin K, are synthesized in plants via the shikimate pathway are also derived from chorismic acid. Since chorismic acid is not the immediate precursor of the benzene ring of vitamin K, it probably is also not the immediate precursor of plant quinones such as alizarin, lucidin, or juglone. ... 

Despite some uncertainties due to early observations in this area s, the biosynthetic pathway to several plant naphthoquinones has been shown to involve (—)-shikimic acid and its metabolites. Thus the nucleus of both juglone (99) and lawsone (100) has been shown to be formed directly from (—)-shikimic acid (107) and a Cj fragment derived from L-glutamic acid. The pattern of experimental results follows closely that obtained in the case of the bacterial mena-quinones (vitamin K2). 

A group of natural and synthetic dyestuffs based on the naphthoquinone structure (phenolic) have found use in the formation of lake and other pigments. Naphthoquinones are found in the leaves, blossoms, wood, bark, roots and fruit of about 20 different species. Those which are found in pigment use are AUcannin and Alkannan in AUcanet from plant species such as Alkanna lehmannii Tineo (formerly known as Alkanna tinctoria Tausch.), Macrotomia spp., Onosma spp. and juglone in Walnut qq.v.) fiom Juglans spp. 

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