Milkweeds

Milkweed Millamine 5260 Milled asbestos fibers Milled fibers Milled soap Millerite... 

Some insects can protect themselves against the toxins present in their food plants by storing them. One example is the monarch butterfly, the caterpillars of which store potentially toxic cardiac glycosides obtained from a food plant, the milkweed (see Harborne 1993). Subsequently, the stored glycosides have a deterrent effect upon blue jays that feed upon them. 

The rubber industry has a long and colorful history. Natural rubber is produced from latex, a milky fluid found in cells that lie between the bark and the wood of many plants. You may have seen latex flow from the broken stalks of milkweed plants, but the source of commercial rubber is the Hevea tree, a native of Brazil. When the bark of this tree is slashed, its milky white sap oozes out and can be collected in cups mounted on the tree s trunk. The people of the Amazon jungle made bouncing balls, shoes, and water Jars out of rubber, and Portuguese explorers sent waterproof boots and a rubber-coated coat back to their king. The first commercial exports included some rubber shoes shipped to Boston in 1823. 

The HPLC analysis of milkweed, the food-plant source for Monarch butterflies, demonstrates that it contains a complex mixture of carotenoids including lutein, several other xanthophylls, xanthophyll epoxides, and (3-carotene, Figure 25.3b. There is a component in the leaf extract that is observed to elute near 8min, which has a typical carotenoid spectrum but is not identical to that of the lutein metabolite observed at near the same retention time in the extracts from larval tissue. 

Monarch epidermis. Peaks seen at 8.7, 10, and 82min are 3-hydroxy-10 -apo-P-carotenal, lutein, zeaxanthin, and P-carotene, respectively. The peak seen eluting at 22 min is the internal standard, monopropyl lutein ether, (b) The chromatogram obtained from an extract of the leaves of the milkweed plant. Peaks eluting prior to lutein are xanthophylls and epoxy xanthophylls, identified components include lutein, zeaxanthin, P-carotene, and its crT-isomer, eluting at 10, 11, 41, 77, and 79min, respectively. 

Mebsa D., Reussa E., and Schneider M. (2005). Studies on the cardenolide sequestration in African milkweed butterflies (Danaidae). Toxicon 45 581-584. 

Ackery, P. R. Vane-Wright, R. I. (1984) Milkweed Butterflies Their Cladistics and Biology (Cornell Univ. Press, Ithaca, NY). 

It can also be made by nitrating diethyl phenyl phosphate below 0°. It is a red oil, almost insoluble in water, and Schrader found it effective against aphids, while Ball and Allen1 proved it active against the housefly, milkweed bug and cockroach. Later work showed it active against the two-spotted spider mite. 

The relationship between milkweeds and the monarch butterfly demonstrates a synergistic relationship between a plant and an insect (Harborne, 1993). The larvae of the monarch butterfly feed on milkweeds and accumulate cardenolides. Birds feeding on the caterpillars, pupae, or adults, will vomit and subsequently become averted and thus avoid the monarch butterflies. Interestingly, other butterflies, such as viceroy, which do not feed on milkweed, have evolved with nearly identical color pattern (mimicry), so birds avoid these nontoxic insects as well. 

Asclepias (milkweeds), and eardiotoxie genins from Nerium (oleander)(Knight and Walter, 2001). 

Benson, J. M., Seiber, J. N., Bagley, C. V., etal. (1979). Effects on sheep of the milkweeds Asckpias eriocarpa and A. labriformis and of cardiac glycoside-containing derivative materials. Toxicon 17,155-165. 

Nelson, C. J., Seiber, J. N., and Brower, L. P. (1981). Seasonal and intraplant variation of cardenolide content in the California milkweed, A5c/ep/(M eriocarpa, and implications for plant defense. Jowrna/ of ChemicalEcobgy 7,981-1010. 

Glycoside diversification also has occurred in the coevolution of monarch butterflies and milkweeds (7). It may be desirable to relate the toxicity of cardenolides to the hydrolytic capabilities of susceptible and nonsusceptible insects. Cardenolides from Rsclepias species can be hydrolyzed by 3-glucosidases present in the plant (6), yet specialized Danans species are able to sequester these compounds, a process wh ich requires control of hydrolysis. 

Cardenolldes appear to be metabolized by a variety of species, possibly as a mechanism for converting these steroids into compounds that can be efficiently sequestered. The milkweed bug, Oncopeltus fasclatus, metabolizes (hydroxylates ) the nonpolar cardenollde dlgltoxln to more polar compounds that are subsequently sequestered In the dorsolateral space fluid (17. 18). Larvae of another cardenolide-adapted Insect, the monarch butterfly, Danaus plexlppus. also convert these steroids Into compounds that are readily sequestered. For example, uscharldln, which contains a carbonyl group at C-3 ( ) of the... 

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