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Title: Repellency of two terpenoid compounds isolated from Callicarpa americana (Lamiaceae) against Ixodes scapularis and Amblyomma americanum ticks.

item Carroll, John
item Cantrell, Charles
item Klun, Jerome
item Kramer, Matthew

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2007
Publication Date: 3/13/2007
Citation: Carroll, J.F., Cantrell, C.L., Klun, J.A., Kramer, M.H. 2007. Repellency of two terpenoid compounds isolated from Callicarpa americana (Lamiaceae) against Ixodes scapularis and Amblyomma americanum ticks. Experimental and Applied Acarology. 41:215-224.

Interpretive Summary: Callicarpenal (13, 14, 15, 16-tetranor-3-clerodenal) and intermedeol [(4S, 5S, 7R, 10S)-eudesm-11-en-4-ol], isolated from American beautyberry, Callicarpa americana (Verbenaceae), were evaluated in laboratory bioassays for repellent activity against nymphs of the blacklegged ticks, Ixodes scapularis, and lone star ticks, Amblyomma americanum. A strip of organdy cloth treated with test solution was doubly wrapped (treatment on outer layer) around the middle phalanx of a forefinger and ticks released on the fingertip. Callicarpenal and intermedeol, at 155 nmole/cm2 cloth, repelled 98% and 96% of I. scapularis nymphs, respectively. Dose response tests with I. scapularis nymphs showed no difference in repellency among callicarpenal, intermedeol and deet (N,N-diethyl-3- methylbenzamide), however SS220 [(1S, 2'S)-2-methylpiperidinyl-3-cyclohexene-1-carboxamide] was significantly more repellent than the other compounds. Callicarpenal, at 155 nmole/cm2 cloth, repelled 100 and 53.3% of I. scapularis nymphs at 3 and 4 h, respectively, after treatment of the cloth. Intermedeol repelled 72.5% of I.. scapularis nymphs at 3 h after treatment. Callicarpenal, intermedeol, deet and SS220 were less effective against A. americanum than against I. scapularis. At 155 nmole/cm2 cloth, only intermedeol and SS220 repelled significantly more A. americanum than ethanol controls. At 1,240 nmole/cm2 cloth, callicarpenal and intermedeol repelled 20 and 40%, respectively, of A. americanum nymphs.

Technical Abstract: Blacklegged (deer) ticks and lone star ticks are of medical importance in many areas of the U.S. Repellents are a last line of personal protection against tick bites. In Mississippi, as a traditional practice to protect draft animals from against biting insects, leaves of American beautyberry, Callicarpa americana, were rubbed on the animals’ coats and stuck under their harnesses. In laboratory bioassays, we tested two compounds, callicarpenal and intermedeol, extracted from C. americana leaves, for their efficacy in repelling blacklegged and lone star ticks and compared the compounds with the repellents deet and SS220. Callicarpenal and intermedeol were as effective as deet in repelling blacklegged tick nymphs. Greater concentrations of callicarpenal, intermedeol, deet and SS220 were needed to repel lone star tick nymphs than blacklegged tick nymphs. Callicarpenal and intermedeol retained their repellency against blacklegged ticks for 3 h after application. Callicarpenal and intermedeol warrant further evaluation as repellents. The history of benign use of C. americana foliage in traditional animal husbandry and the compounds’ persistent repellent activity suggest that callicarpenal and intermedeol have potential for commercial development. These results are also of interest to researchers seeking new means of personal protection against tick bite.