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Carissa Braun
12,476 followers -
Biologist, Naturalist, Photographer, Writer
Biologist, Naturalist, Photographer, Writer

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Beautyberry Bug Bites: Callicarpenal and Intermedeol

American Beautyberry is perennial, many-branched deciduous shrub found within the southeastern United States down into Mexico and the West Indies. It is one of approximately 135 species of Callicarpa found throughout the world, but American Beautyberry, Callicarpa americana, is the only species native to the United States. American beautyberry can grow up to 2.7 m (9 ft) in favorable conditions of partial shade and moist soil, but averages 1-1.5 m (3-5 ft) and is drought tolerant. The pale pink flowers become trademark bright, iridescent purple berry clusters along the stems from autumn into winter, though it should not be confused with the unrelated smaller-leafed coralberry. The berries are a favorite of many species of birds and mammals and can be made into a jam for human consumption. Native Americans used the roots, leaves, and berries to treat rheumatism, fevers, malaria, dysentery, and colic, but one of the most interesting aspect of beautyberry that has gained it attention is its potential as an effective insect repellent.

Early 20th century farmers helped bring American beautyberry to light as they would crush the leaves and place them under the harnesses of their horses and mules to repel biting flies and mosquitoes. In addition, about 20 other species of Callicarpa have reported *ethnobotanical and ethnomedical uses, especially in China and South Asia. They were similarly used for digestion, fever, and rheumatism as well as for hepatitis, skin cancer, intestinal cancer, to regulate fertility, and as a fish poison. In evaluating different species of Callicarpa for biological activity, researchers discovered antibacterial, antifungal, anti-insect growth, cytotoxic, and phytotoxic activities. Amino acids, benzenoids, simple carbohydrates, lipids, diterpenes, flavonoids, phenylpropanoids, phytosterols, sesquiterpenes, and triterpenes have been detected or isolated. In Callicarpa americana specifically, the essential oils are reported to have antialgal and phytotoxic activities, many of which contribute to the mosquito bite-deterrent activity first reported. Three compounds in particular, callicarpenal, spathulenol, and intermedeol, show significant repellent activity – spathulenol from Japanese Beautyberry, Callicarpa japonica and callicarpenal and intermedeol from American Beautyberry, Callicarpa americana.

Callicarpenal and intermedeol have been extensively studied in their repellent activity. Both compounds have shown significant bite-deterring activity against the yellow fever mosquito, Aedes aegypti, and a malaria-vector mosquito, Anopheles stephensi, show promise against the blacklegged tick, Ixodes scapularis, the lone star tick, Amblyomma americanum, and the Cayenne tick, Amblyomma cajennense, and are being evaluated against red imported fire ants, Solenopsis invicta, black imported fire ants, Solenopsis richteri, and a hybrid of the two species. Against I. scapularis, callicarpenal and intermedeol showed significant repellent activity equal with Deet, but against A. americanum, Deet and SS220 were less effective compared to callicarpenal and intermedeol. A low concentration of both were effective against both imported ants and the hybrid of the species, but intermedeol showed significantly greater repellency.

While studies are promising, effective isolation and production of these compounds is an obstacle. For callicarpenal, dry biomass results in a low isolation yield of 0.05-0.15%. The tedious bulk isolation and purification techniques substantially restricts the natural availability, but there is hope. One particularly efficient enantioslective synthesis of (-)-callicarpenal proceeds in 12 steps, results in a 36% overall yield from diketone, and utilizes readily available materials and reagents. In addition, studies have shown the chemical structure of the parent molecule can be simplified without significant loss of activity. Similar synthesis studies have been conducted on intermedeol and spathulenol.

American beautyberry and others of the Callicarpa genus hold promise for a range of purposes, but there is still research to be done. While it has potential for a great variety of biological activities, it has currently drawn the most interest in its insect repellent properties. It may be years or decades until it becomes available for commercial use and an effective alternative to other repellents, but it is very likely that day will come. Until then, American beautyberry makes for a lovely shrub in many yards, forests, and plains.


A piece for your #ScienceSunday  consumption, and no, there is no research on its repellent activity against assassin bugs, but I keep finding them hanging around my plant, not that I'm complaining! I will also add that while the berries are edible, there is a reason you find them in jam as they aren't very palatable otherwise.


Sources and Further Reading:
Lady Bird Johnson Wildflower Center: Callicarpa americana
http://goo.gl/2vo0RL (Native Plant Database | website)
American Beautyberry: Callicarpa americana
http://goo.gl/iLXQfo (USDA Plant Fact Sheet | pdf)
Wildlife Resources Management Manual: American Beautyberry
http://goo.gl/GmVChj (U.S. Army Corps of Engineers | pdf)
Biologically Active Natural Products of the Genus Callicarpa
http://goo.gl/aNF44j (NCBI PMC | website)
Callicarpenal and Intermedeol...
http://goo.gl/pMHjfP (ACS Symposium Series | website)
Repellency of two terpenoid compounds from Callicarp americana...
http://goo.gl/qIM4II (NCBI PMC | website)
Repellency of callicarpenal and intermedeol against…
http://goo.gl/u0iozx (NCBI PMC | website)
Synthesis of (-)-callicarpenal, a potent anthropod-repellent
http://goo.gl/g6kdwS (NCBI PMC | website)
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