Rhododendron species

The naturally occurring llavones are yellow and are very widely distributed in plants. They accumulate in almost any part of a plant, from the roots to the flower petals. Unlike the anthocyanins, which are too reactive and short-lived, the much more stable llavones have, from time immemorial, been used as dyes, for they impart various shades of yellow to wool. As an example, the inner bark of one of the North American oaks, Quercus velutina, was a commercial material known as quercitron bark and much used in dyeing it contains quercetrin. The corresponding aglycone, quercetin, is one of the most widely occurring flavones, found, for example, in Chrysanthemum and Rhododendron species, horse chestnuts, lemons, onions and hops. 

Rhododendron species are far distributed on the Northern hemisphere and in Australia. Poisoning has been observed in humans and in animals, the most important substance responsible being andromedotoxin (=Acetylandromedol) (48, 49). Usually the whole plant is toxic, including pollen and nectar which is... 

The corresponding aglycone, quercetin, is one of the most widely occurring flavones, found, for example, in Chrysanthemum and Rhododendron species, horse chestnuts, lemons, onions, and hops. 

Taraxeral (14-taraxeren-3jS-ol). Formula, see triterpenes. C30H50O, Mr 426.73, mp. 282-283 °C, [ajp -t0.7° (CHCI3). T. is a triterpene widely distribute in the plant kingdom, isolated for the first time in 1923 from the bark of gray alder (Alntts incana). T. also occurs in the roots of dandelion (Taraxacum officinale), in various alder species, rhododendron species, and Euphoibiaceae, as well as in some lichens. T. is derived from the taraxerane skeleton and has antigastritic properties. 

C30H48O3, Mr 456.71, mp. 291 °C, [a]n +66° (C2H5OH), somewhat soluble in methanol and ether. U. is a triterpene carboxylic acid with the ursane skeleton (see triterpenes) isolated for the first time in 1854 by Trommsdorf from the leaves of the bearberry (Arcto-staphylos uva-ursi). U. occurs in many plants such as, e.g., in leaves and berries of Vaccinium, Arbutus, Erica, and Rhododendron species, in wax coatings of apples and pears, in the fruit skins of cranberries and bilberries, in thyme, marjoram, rosemary, sage. U. exhibits cytotoxic and antileukemic activities. 

Rhododendron species. In providing the name of the 10 multifloranes known to date, Gelonium multiflorum contains (-)-7-multifloren-3p-ol (multiflorenol) in the leaves the methylether is a constituent of the wax of flie leaves of sugar cane Sac-charum officinarum (Poaceae). The term of rarely abundant baueranes stems from Achronychia baueri with (-)-7-baueren-3p-ol as a constituent which also occurs in Ilex species (Aquifoliaceae), giving rise to the synonym ilexol. 

More than 150 ursanes of plant origin are documented (+)-3p-Hydroxyursan-28-oic acid, for example, represents a saturated triterpene found in the leaves of oleander Nerium oleander (Apocynaceae). (-l-)-3p-Hydroxy-12-ursen-28-oic acid is the most prominent derivative this was first isolated from the leaves and berries of bearberry Arctostaphylos uva-ursi, and therefore is commonly known as ursolic acid. It is also found in Rhododendron species, in cranberries Vaccinum macrocar-pon (Ericaceae), and in the protective wax coating of apples, pears, prunes, and other fruits. Ursolic acid is reported to have antileukemic and cytotoxic activities it is also used as an emulsifier in pharmaceuticals and foods, and is similar to (-1-)-3p,19a-dihydroxy-12-ursen-28-oic acid (known as pomolic acid) extracted from the wax coats of apples. 

Poisonous honey (pontius or insane honey) has been known since the time of the Greek historian and general, Xenophon, and the Roman writer, Plinius, It comes mostly from bees collecting their nectar from rhododendron species (Asia Minor, Caucasus Mountains) some plants of the... 

Table 4.8 Percentage flavonoid aglycone occurrence in species of Rhododendron sect. Vireya (from Harborne, 1986)...

The best known species is Laurus nob ills, a Mediterranean shrub used by the ancient Greeks to decorate the head of victors in the Pythian games, which led to modem phrases such as poet laureate and Nobel laureate. Additional well-known species include avocado, California laurel, sassafras, and cinnamon tree. American gardeners often refer to Kalmia latifolia as mountain laurel, and to Rhododendron maximum as great laurel, despite the fact that both of these shrubs are in the Ericaceae family, and are unrelated to the true laurels of the Lauraceae. 

Leaves with spots. Cause Leaf spots. Several species of fungi cause leaf spots on rhododendrons and azaleas. 

Damage Larvae bore into stems of currants, gooseberries, raspberries, and rhododendrons. Their tunneling can weaken canes, causing them to break easily, or can kill entire canes. Larvae boring into crowns girdle canes and destroy new shoots. These species are related to peachtree boreis. 

Henbane (Hyoscyamine niger), a sticky, bad-smell-ing weed containing the powerful narcotics hyoscyamine and scopolamine, was also collected as arrow poison in antiquity. Henbane causes violent seizures, psychosis, and death. Other plant juices used on projectiles included hemlock [Conium maculatum), yew (Taxus), rhododendron, and several species of deadly nightshade or belladonna, which causes vertigo, extreme agitation, coma, and death. The... 

Rhododendron is a flowering, green, shrub-like plant. Various species are found throughout Europe and the United States. 

Canthin-6-one (1) has been isolated from 25 of the 36 species of plants in Table I and from cell cultures of Ailanthus altissima (13-16). Canthin-6-one is one of the most widely distributed alkaloids in plants. It has been reported (77) that 1 is contained in 9 of 33 species in the genus Rhododendron of the family Ericaceae of China. Readers are referred to Volume 8 (p. 249) of this treatise for its structure (5). 

Class Index C22 Grayanotoxins CAS — hypotensive action. leaves of various species of Rhododendrons. Grayanotoxins are crystalline materials that are soluble in hot water and alcohols. 

Grayanotoxins. Toxic diterpenoids present in leaves of the various species of Rhododendron. Kalmia, and Leucothoe. Ericaceae also found in honey from rhododen-... 

GrayaiMtoxins. Toxic diterpenoids from leaves of Ericaceae species (Ericaceae diterpenes), e. g. Rhododendron maximum or Leucothoe grayana. G. also occur in the nectar of rhododendron flowers. Mass poisonings through contaminated honey even occurred in Antiquity. About 25 G. have been isolated. The most important are G. 1, II, and III (see table). 

A compound of this structure was first isolated from Matteucia orientalis by Munesada (12) and was named (-)-matteucinol. Later the isolation of matteucinol was reported from two species of Rhododendron, by Arthur and Hui (13) and by Tanabe, Kondo and Takahashi (14) however, the structuri assignments were not unequivocal since no spectral data was reported. Thus, this paper provides the first report of the spectral data of (-)-matteucinol and confirms the structure assignment as 5,7-dihydroxy-a,5-dimethyM -methoxyflavanone. 

Height reduction can be achieved with virtually all of the new compounds in many ornamental plant species such as chrysanthemum, poinsettia, tulip, azalea, and lily [4, 20, 23, 35, 49]. The formation of flower buds was promoted by uniconazole in azalea and rhododendron [35]. 

Certain species of rhododendron contain grayanotoxins (andromedotoxins), which open sodium channels. In the heart this effect can trigger the Bezold-Jarisch reflex and cause bradycardia, heart block, asystole, and hypotension [79 ]. 

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