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The scent of the reticulated giraffe (Giraffa camelopardalis reticulata)
Biochemical Systematics and Ecology 30 (2002) 913–917 www.elsevier.com/locate/biochemsyseco
The scent of the reticulated giraffe (Giraffa camelopardalis reticulata) William F. Wood a,∗, Paul J. Weldon b b
a Department of Chemistry, Humboldt State University, Arcata, California 95521, USA Conservation and Research Center, Smithsonian Institution, 1500 Remount Road, Front Royal, VA 22630, USA
Received 13 August 2001; accepted 7 December 2001
Abstract The giraffe (Giraffa camelopardalis) emits a scent that can be detected by humans over considerable distances. Dichloromethane extracts of hair samples from adult male and female reticulated giraffes (G. c. reticulata) were analysed by gas chromatography–mass spectrometry. Two highly odoriferous compounds, indole and 3-methylindole, identified in these extracts appear to be primarily responsible for the giraffe’s strong scent. Other major compounds identified were octane, benzaldehyde, heptanal, octanal, nonanal, p-cresol, tetradecanoic acid, hexadecanoic acid, and 3,5-androstadien-17-one; the last compound has not previously been identified from a natural source. These compounds may deter microorganisms or ectoparasitic arthropods. Most of these compounds are known to possess bacteriostatic or fungistatic properties against mammalian skin pathogens or other microorganisms. The levels of p-cresol in giraffe hair are sufficient to repel some ticks. 2002 Elsevier Science Ltd. All rights reserved. Keywords: Giraffa camelopardalis reticulata; Giraffe; Scent; Anti-ectoparasitic agents; Antimicrobial activity
1. Introduction Naturalists and hunters have long noted the strong scent emanating from the pelage of the giraffe (Giraffa camelopardalis) (Dagg and Foster, 1976). Percival (1924) ∗
Corresponding Author. Tel. +1-707-826-3109; fax +1-707-826-3279. E-mail address: [email protected] (W.F. Wood).
0305-1978/02/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 3 0 5 - 1 9 7 8 ( 0 2 ) 0 0 0 3 7 - 6
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W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
stated that he could detect giraffes while standing more than 250 m downwind from them. Cumming (1870) found the scent pleasant, reminding him of “a hive of heather honey in September,” but others regard it as unpleasant (Baldwin, 1894; Percival, 1924). Fitzsimons (1920), for example, stated that old bulls emit “a most disagreeable, musky, nauseating odour.” Other species may also respond negatively to the scent of giraffes. Horses reportedly react “strongly” to it (Dagg and Foster, 1976). Fitzsimons (1920) suggested that giraffe scent repels lions and other predators, but no tests of this or of other possible functions have been reported. We report our analysis of hair and associated epidermal material from adult reticulated giraffes (G. c. reticulata). Our results indicate the presence of a number of volatile compounds; two that are highly odoriferous to humans, many that have demonstrated bacteriostatic or fungistatic activity against microbes that inhabit mammalian skin, and one that repels an African ixodid tick. In addition, we report an androstanone, 3,5-androstadien-17-one, not previously known from a natural source.
2. Materials and methods Hair samples of G. c. reticulata were obtained during August, 2000, from a 630 kg, 12.4 year-old male and a 443 kg, 17.4 year-old female. Both were captive-born. Their diet consisted of Romaine lettuce, spinach, Mazuri Bovine Browser Breeder, and Mazuri Leaf Eater Primate Diet (PMI Nutrition Int., Inc., Brentwood, Missouri); the commercial feeds contain soybean hulls, wheat middlings, oats, alfalfa meal, corn, dried apple pomace, and vitamins. For sample collection, the animals were individually confined in a squeeze stall. Hair and associated epidermal materials were collected by scraping the edge of glass slides against the dorsum, shoulder and neck of each individual; these regions were selected to avoid contamination by urine and/or faeces. The hair samples were placed into separate glass vials, stored frozen (⫺20 °C) and then extracted with dichloromethane for analyses. Gas chromatography–mass spectrometry (GC–MS) was performed on the dichloromethane extracts in a splitless mode (0.5 mm), using a Hewlett-Packard GCD Plus fitted with a 30 m × 0.25 mm cross-linked phenyl methyl silicone capillary column (HP-5MS). The gas chromatograph was programmed so the oven temperature was kept at 40 °C for 4 min, then increased to a final temperature of 325 °C at a rate of 30 °C/min. Mass spectral fragments below m/z=39 were not recorded. The relative amount of each component is reported as the percent of the total ion current (TIC). Minor components less than 2% of the TIC were not investigated, and impurities found in the solvent were subtracted from the analyses. All compounds were initially identified by comparison of mass spectra in the NIST 1998 computerised mass spectral library. These identifications were confirmed by comparison of spectra and retention times to those of authentic standards [SigmaAldrich Chemical Co., Milwaukee, Wisconsin, and Fisher Scientific (Amos), Pittsburgh, Pennsylvania.] The quantity of p-cresol in the pelage was determined by GC– MS comparison to standard amounts.
W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
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3. Results and discussion Eleven major volatile compounds were found in the dichloromethane extracts of both male and female G. c. reticulata. These consisted of an alkane (octane), four aldehydes (benzaldehyde, heptanal, octanal, and nonanal), a phenol (p-cresol), two alkaloids (indole and 3-methylindole), two carboxylic acids (tetradecanoic and hexadecanoic acids), and a steroid (3,5-androstadien-17-one). The relative amounts of these compounds obtained from the male and female are listed in Table 1. We have not investigated the source of these skin chemicals. Sebaceous and apocrine glands, which are widely distributed over the body surface of giraffes (Dimond and Montagna, 1976), and the epidermis, which may produce lipids during keratinization, seem likely sources for these compounds. The two alkaloids, indole and 3-methylindole (skatole), are primarily responsible for the scent of the giraffe. Several human subjects were presented with samples of indole and/or 3-methylindole and agree that they closely simulate the natural odour. Indole occurs naturally in the floral scent of jasmine, orange blossom and other flowers (Poucher, 1974). Indole and 3-methylindole have an intense faecal odour at high concentrations that becomes pleasant in very dilute solutions — both are used in perfumery (Poucher, 1974). Neither of these alkaloids was observed in hair samples obtained from adult male and female okapi (Okapia johnstoni), the closest extant relative of giraffes (Wood and Weldon, unpublished). Many of these compounds may function as antimicrobial agents. Trichophyton mentagrophytes, a widely distributed zoophilic skin fungus responsible for athlete’s foot and many other human skin infections, is inhibited by indole (Kubo et al., 1992; Oimomi et al., 1972), nonanal (Kubo et al., 1995), and tetradecanoic and hexadecanoic acids (Garg and Mueller, 1993). The related T. rubrum is reported to be Table 1 The major volatile compounds identified from the skin of male and female Giraffa camelopardalis reticulata. Values are reported as the percent of the total ion current (TIC) Compound
Male (%TIC)
Female (%TIC)
Octane Benzaldehyde Heptanal Octanal Nonanal p-Cresol Indole 3-Methylindole Tetradecanoic acid Hexadecanoic acid 3,5-Androstadien-17-one Minor compoundsa
5.6 3.7 5.3 2.9 22.5 5.5 6.5 14.0 8.1 11.9 8.1 6.0
6.9 5.7 2.3 3.6 28.9 3.0 3.0 4.7 11.4 11.3 6.9 12.5
a
Minor compounds less than 2% of the TIC were not identified.
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W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
inhibited by octanal and nonanal (Kurita et al., 1981), and also by tetradecanoic and hexadecanoic acids (Garg and Mueller, 1993). The zoophilic fungus, Microsporum canis, is inhibited by tetradecanoic and hexadecanoic acids (Garg and Mueller, 1993). The growth of two ubiquitous species of skin bacteria is inhibited by some of the giraffe-derived compounds. Staphylococcus aureus is inhibited by indole (Kubo et al., 1992; Morris et al., 1979), benzaldehyde (Morris et al., 1979), octanal (Inouye et al., 1983; Morris et al., 1979), p-cresol (Morris et al., 1979), tetradecanoic acid (Kabara et al., 1972), hexadecanoic acid (Hogan et al., 1987) and nonanal (Kubo et al., 1995). Propionibacterium acnes, the human acne-causing bacterium, is also found on many other mammals. It is inhibited by nonanal (Kubo et al., 1995) and indole (Kubo et al., 1992, 1994). In most cases, the antimicrobial activity of these compounds is moderate; however, acting synergistically their activity could be more potent. Indole has been shown to increase the activity of caryophyllene against the human tooth decay bacterium, Streptococcus mutans, and also P. acnes (Kubo et al., 1992). When indole was added at one half of the amount needed for inhibition, the minimum inhibitory concentration (MIC) of caryophyllene against S. mutans went from 1600 to 6.25 µg/mL. Similar tests with P. acnes showed the MIC to drop from 6.5 to 3.13 µg/mL. Another possible function of these compounds may be to repel ectoparasitic arthropods. Both indole and skatole were judged by Rudolfs (1922, 1930) to repel wildcaught mosquitoes (Aedes spp.) from the US, but quantitative results are needed to affirm this. A tick found in areas inhabited by giraffes, Rhipicephalus appendiculatus, is repelled by p-cresol, one of the giraffe skin compounds (Wood et al., 1975). The amount of p-cresol in giraffe hair and the amount that was repellent to ticks are of the same order of magnitude. Analysis of giraffe hair samples showed 0.13 g of the male’s and 0.14 g of the female’s hair to contain 1.08×10⫺6 g of p-cresol, the minimum amount reported to repel these ticks. Further studies are needed on the effects of this compound and other giraffe compounds on hematophagous arthropods.
Acknowledgements J. Durham, M. Fincher, and R. Reed (Silver Springs Wild Animal Park, Silver Springs, FL) made giraffes available for this study.
References Baldwin, W.G., 1894. African Hunting and Adventure from Natal to the Zambesi. Richard Bentley and Son, London. Cumming, R.G., 1870. The Lion Hunter of South Africa, sixth ed. John Murray, London. Dagg, A. I, Foster, J.B., 1976. The Giraffe: Its Biology. Behavior and Ecology, Van Nostrand Reinhold Co., New York. Dimond, R.L., Montagna, W., 1976. The skin of the giraffe. Anat. Rec. 185, 63–76. Fitzsimons, F.W., 1920. The Natural History of South Africa, vol 3. Longmans, Green, London. Garg, A.P., Mueller, J., 1993. Fungitoxicity of fatty acids against dermatophytes. Mycoses 36, 51–63.
W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
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Hogan, J.S., Pankey, J.W., Duthie, A.H., 1987. Growth inhibition of mastitis pathogens by long-chain fatty acids. J. Dairy Sci. 70, 927–934. Inouye, S., Goi, H., Miyauchi, K., Muraki, S., Ogihara, M., Iwanami, Y., 1983. Inhibitory effect of volatile constituents of plants on the proliferation of bacteria: Antibacterial activity of plant volatiles. Bokin Bobai 11, 609–615. Kabara, J.J., Swieczkowski, D.M., Conley, A.J., Truant, J.P., 1972. Fatty acids and derivatives as antimicrobial agents. Antimicrob. Agents Chemother. 2, 23–28. Kubo, I., Muroi, H., Himejima, M., 1992. Antimicrobial activity of green tea flavor components and their combination effects. J. Agric. Food Chem. 40, 245–248. Kubo, I., Muroi, H., Kubo, A., 1994. Naturally occurring antiacne agents. J. Nat. Prod. 57, 9–17. Kubo, A., Lunde, C.S., Kubo, I., 1995. Antimicrobial activity of the olive oil flavor compounds. J. Agric. Food Chem. 43, 1629–1633. Kurita, N., Miyaji, M., Kurane, R., Takahara, Y., 1981. Antifungal activity of components of essential oils. Agric. Biol. Chem. 45, 945–952. Morris, J.A., Khettry, A., Seitz, E.W., 1979. Antimicrobial activity of aroma chemicals and essential oils. J. Am. Oil Chem. Soc. 56, 595–603. Oimomi, M., Hamada, M., Hara, T., 1972. Antimicrobial activities of indole. J. Antibiot. 27, 987–988. Percival, A.B., 1924. A Game Ranger’s Note Book. Nisbet, London. Poucher, W.A., 1974. Perfumes, Cosmetics and Soaps, seventh ed. Chapman and Hall, London. Rudolfs, W. 1922. Chemotropism of mosquitoes. N.J. Agric. Exp. Sta. Bull. no 367. Rudolfs, W. 1930. Effect of chemicals upon the behavior of mosquitoes. Bull. N.J. Agric. Exp. Sta. no 496. Wood, W.F., Leahy, M.G., Galun, R., Prestwich, G.D., Meinwald, J., Purnell, R.F., Payne, R., 1975. Phenols as sex pheromones of ixodid ticks: a general phenomenon? J. Chem. Ecol. 1, 501–509.
The scent of the reticulated giraffe (Giraffa camelopardalis reticulata) William F. Wood a,∗, Paul J. Weldon b b
a Department of Chemistry, Humboldt State University, Arcata, California 95521, USA Conservation and Research Center, Smithsonian Institution, 1500 Remount Road, Front Royal, VA 22630, USA
Received 13 August 2001; accepted 7 December 2001
Abstract The giraffe (Giraffa camelopardalis) emits a scent that can be detected by humans over considerable distances. Dichloromethane extracts of hair samples from adult male and female reticulated giraffes (G. c. reticulata) were analysed by gas chromatography–mass spectrometry. Two highly odoriferous compounds, indole and 3-methylindole, identified in these extracts appear to be primarily responsible for the giraffe’s strong scent. Other major compounds identified were octane, benzaldehyde, heptanal, octanal, nonanal, p-cresol, tetradecanoic acid, hexadecanoic acid, and 3,5-androstadien-17-one; the last compound has not previously been identified from a natural source. These compounds may deter microorganisms or ectoparasitic arthropods. Most of these compounds are known to possess bacteriostatic or fungistatic properties against mammalian skin pathogens or other microorganisms. The levels of p-cresol in giraffe hair are sufficient to repel some ticks. 2002 Elsevier Science Ltd. All rights reserved. Keywords: Giraffa camelopardalis reticulata; Giraffe; Scent; Anti-ectoparasitic agents; Antimicrobial activity
1. Introduction Naturalists and hunters have long noted the strong scent emanating from the pelage of the giraffe (Giraffa camelopardalis) (Dagg and Foster, 1976). Percival (1924) ∗
Corresponding Author. Tel. +1-707-826-3109; fax +1-707-826-3279. E-mail address: [email protected] (W.F. Wood).
0305-1978/02/$ - see front matter 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 3 0 5 - 1 9 7 8 ( 0 2 ) 0 0 0 3 7 - 6
914
W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
stated that he could detect giraffes while standing more than 250 m downwind from them. Cumming (1870) found the scent pleasant, reminding him of “a hive of heather honey in September,” but others regard it as unpleasant (Baldwin, 1894; Percival, 1924). Fitzsimons (1920), for example, stated that old bulls emit “a most disagreeable, musky, nauseating odour.” Other species may also respond negatively to the scent of giraffes. Horses reportedly react “strongly” to it (Dagg and Foster, 1976). Fitzsimons (1920) suggested that giraffe scent repels lions and other predators, but no tests of this or of other possible functions have been reported. We report our analysis of hair and associated epidermal material from adult reticulated giraffes (G. c. reticulata). Our results indicate the presence of a number of volatile compounds; two that are highly odoriferous to humans, many that have demonstrated bacteriostatic or fungistatic activity against microbes that inhabit mammalian skin, and one that repels an African ixodid tick. In addition, we report an androstanone, 3,5-androstadien-17-one, not previously known from a natural source.
2. Materials and methods Hair samples of G. c. reticulata were obtained during August, 2000, from a 630 kg, 12.4 year-old male and a 443 kg, 17.4 year-old female. Both were captive-born. Their diet consisted of Romaine lettuce, spinach, Mazuri Bovine Browser Breeder, and Mazuri Leaf Eater Primate Diet (PMI Nutrition Int., Inc., Brentwood, Missouri); the commercial feeds contain soybean hulls, wheat middlings, oats, alfalfa meal, corn, dried apple pomace, and vitamins. For sample collection, the animals were individually confined in a squeeze stall. Hair and associated epidermal materials were collected by scraping the edge of glass slides against the dorsum, shoulder and neck of each individual; these regions were selected to avoid contamination by urine and/or faeces. The hair samples were placed into separate glass vials, stored frozen (⫺20 °C) and then extracted with dichloromethane for analyses. Gas chromatography–mass spectrometry (GC–MS) was performed on the dichloromethane extracts in a splitless mode (0.5 mm), using a Hewlett-Packard GCD Plus fitted with a 30 m × 0.25 mm cross-linked phenyl methyl silicone capillary column (HP-5MS). The gas chromatograph was programmed so the oven temperature was kept at 40 °C for 4 min, then increased to a final temperature of 325 °C at a rate of 30 °C/min. Mass spectral fragments below m/z=39 were not recorded. The relative amount of each component is reported as the percent of the total ion current (TIC). Minor components less than 2% of the TIC were not investigated, and impurities found in the solvent were subtracted from the analyses. All compounds were initially identified by comparison of mass spectra in the NIST 1998 computerised mass spectral library. These identifications were confirmed by comparison of spectra and retention times to those of authentic standards [SigmaAldrich Chemical Co., Milwaukee, Wisconsin, and Fisher Scientific (Amos), Pittsburgh, Pennsylvania.] The quantity of p-cresol in the pelage was determined by GC– MS comparison to standard amounts.
W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
915
3. Results and discussion Eleven major volatile compounds were found in the dichloromethane extracts of both male and female G. c. reticulata. These consisted of an alkane (octane), four aldehydes (benzaldehyde, heptanal, octanal, and nonanal), a phenol (p-cresol), two alkaloids (indole and 3-methylindole), two carboxylic acids (tetradecanoic and hexadecanoic acids), and a steroid (3,5-androstadien-17-one). The relative amounts of these compounds obtained from the male and female are listed in Table 1. We have not investigated the source of these skin chemicals. Sebaceous and apocrine glands, which are widely distributed over the body surface of giraffes (Dimond and Montagna, 1976), and the epidermis, which may produce lipids during keratinization, seem likely sources for these compounds. The two alkaloids, indole and 3-methylindole (skatole), are primarily responsible for the scent of the giraffe. Several human subjects were presented with samples of indole and/or 3-methylindole and agree that they closely simulate the natural odour. Indole occurs naturally in the floral scent of jasmine, orange blossom and other flowers (Poucher, 1974). Indole and 3-methylindole have an intense faecal odour at high concentrations that becomes pleasant in very dilute solutions — both are used in perfumery (Poucher, 1974). Neither of these alkaloids was observed in hair samples obtained from adult male and female okapi (Okapia johnstoni), the closest extant relative of giraffes (Wood and Weldon, unpublished). Many of these compounds may function as antimicrobial agents. Trichophyton mentagrophytes, a widely distributed zoophilic skin fungus responsible for athlete’s foot and many other human skin infections, is inhibited by indole (Kubo et al., 1992; Oimomi et al., 1972), nonanal (Kubo et al., 1995), and tetradecanoic and hexadecanoic acids (Garg and Mueller, 1993). The related T. rubrum is reported to be Table 1 The major volatile compounds identified from the skin of male and female Giraffa camelopardalis reticulata. Values are reported as the percent of the total ion current (TIC) Compound
Male (%TIC)
Female (%TIC)
Octane Benzaldehyde Heptanal Octanal Nonanal p-Cresol Indole 3-Methylindole Tetradecanoic acid Hexadecanoic acid 3,5-Androstadien-17-one Minor compoundsa
5.6 3.7 5.3 2.9 22.5 5.5 6.5 14.0 8.1 11.9 8.1 6.0
6.9 5.7 2.3 3.6 28.9 3.0 3.0 4.7 11.4 11.3 6.9 12.5
a
Minor compounds less than 2% of the TIC were not identified.
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W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
inhibited by octanal and nonanal (Kurita et al., 1981), and also by tetradecanoic and hexadecanoic acids (Garg and Mueller, 1993). The zoophilic fungus, Microsporum canis, is inhibited by tetradecanoic and hexadecanoic acids (Garg and Mueller, 1993). The growth of two ubiquitous species of skin bacteria is inhibited by some of the giraffe-derived compounds. Staphylococcus aureus is inhibited by indole (Kubo et al., 1992; Morris et al., 1979), benzaldehyde (Morris et al., 1979), octanal (Inouye et al., 1983; Morris et al., 1979), p-cresol (Morris et al., 1979), tetradecanoic acid (Kabara et al., 1972), hexadecanoic acid (Hogan et al., 1987) and nonanal (Kubo et al., 1995). Propionibacterium acnes, the human acne-causing bacterium, is also found on many other mammals. It is inhibited by nonanal (Kubo et al., 1995) and indole (Kubo et al., 1992, 1994). In most cases, the antimicrobial activity of these compounds is moderate; however, acting synergistically their activity could be more potent. Indole has been shown to increase the activity of caryophyllene against the human tooth decay bacterium, Streptococcus mutans, and also P. acnes (Kubo et al., 1992). When indole was added at one half of the amount needed for inhibition, the minimum inhibitory concentration (MIC) of caryophyllene against S. mutans went from 1600 to 6.25 µg/mL. Similar tests with P. acnes showed the MIC to drop from 6.5 to 3.13 µg/mL. Another possible function of these compounds may be to repel ectoparasitic arthropods. Both indole and skatole were judged by Rudolfs (1922, 1930) to repel wildcaught mosquitoes (Aedes spp.) from the US, but quantitative results are needed to affirm this. A tick found in areas inhabited by giraffes, Rhipicephalus appendiculatus, is repelled by p-cresol, one of the giraffe skin compounds (Wood et al., 1975). The amount of p-cresol in giraffe hair and the amount that was repellent to ticks are of the same order of magnitude. Analysis of giraffe hair samples showed 0.13 g of the male’s and 0.14 g of the female’s hair to contain 1.08×10⫺6 g of p-cresol, the minimum amount reported to repel these ticks. Further studies are needed on the effects of this compound and other giraffe compounds on hematophagous arthropods.
Acknowledgements J. Durham, M. Fincher, and R. Reed (Silver Springs Wild Animal Park, Silver Springs, FL) made giraffes available for this study.
References Baldwin, W.G., 1894. African Hunting and Adventure from Natal to the Zambesi. Richard Bentley and Son, London. Cumming, R.G., 1870. The Lion Hunter of South Africa, sixth ed. John Murray, London. Dagg, A. I, Foster, J.B., 1976. The Giraffe: Its Biology. Behavior and Ecology, Van Nostrand Reinhold Co., New York. Dimond, R.L., Montagna, W., 1976. The skin of the giraffe. Anat. Rec. 185, 63–76. Fitzsimons, F.W., 1920. The Natural History of South Africa, vol 3. Longmans, Green, London. Garg, A.P., Mueller, J., 1993. Fungitoxicity of fatty acids against dermatophytes. Mycoses 36, 51–63.
W.F. Wood, P.J. Weldon / Biochemical Systematics and Ecology 30 (2002) 913–917
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Hogan, J.S., Pankey, J.W., Duthie, A.H., 1987. Growth inhibition of mastitis pathogens by long-chain fatty acids. J. Dairy Sci. 70, 927–934. Inouye, S., Goi, H., Miyauchi, K., Muraki, S., Ogihara, M., Iwanami, Y., 1983. Inhibitory effect of volatile constituents of plants on the proliferation of bacteria: Antibacterial activity of plant volatiles. Bokin Bobai 11, 609–615. Kabara, J.J., Swieczkowski, D.M., Conley, A.J., Truant, J.P., 1972. Fatty acids and derivatives as antimicrobial agents. Antimicrob. Agents Chemother. 2, 23–28. Kubo, I., Muroi, H., Himejima, M., 1992. Antimicrobial activity of green tea flavor components and their combination effects. J. Agric. Food Chem. 40, 245–248. Kubo, I., Muroi, H., Kubo, A., 1994. Naturally occurring antiacne agents. J. Nat. Prod. 57, 9–17. Kubo, A., Lunde, C.S., Kubo, I., 1995. Antimicrobial activity of the olive oil flavor compounds. J. Agric. Food Chem. 43, 1629–1633. Kurita, N., Miyaji, M., Kurane, R., Takahara, Y., 1981. Antifungal activity of components of essential oils. Agric. Biol. Chem. 45, 945–952. Morris, J.A., Khettry, A., Seitz, E.W., 1979. Antimicrobial activity of aroma chemicals and essential oils. J. Am. Oil Chem. Soc. 56, 595–603. Oimomi, M., Hamada, M., Hara, T., 1972. Antimicrobial activities of indole. J. Antibiot. 27, 987–988. Percival, A.B., 1924. A Game Ranger’s Note Book. Nisbet, London. Poucher, W.A., 1974. Perfumes, Cosmetics and Soaps, seventh ed. Chapman and Hall, London. Rudolfs, W. 1922. Chemotropism of mosquitoes. N.J. Agric. Exp. Sta. Bull. no 367. Rudolfs, W. 1930. Effect of chemicals upon the behavior of mosquitoes. Bull. N.J. Agric. Exp. Sta. no 496. Wood, W.F., Leahy, M.G., Galun, R., Prestwich, G.D., Meinwald, J., Purnell, R.F., Payne, R., 1975. Phenols as sex pheromones of ixodid ticks: a general phenomenon? J. Chem. Ecol. 1, 501–509.