植物精油對貓蚤的忌避活性與應用

Abstract

跳蚤的叮咬不僅騷擾人或寵物，還會傳播一些疾病，如鼠疫。在有跳蚤出現的區域，使用忌避劑來保護個人不受跳蚤叮咬是最普遍的方式。市面上多以合成的忌避劑為主，但考慮到人的健康及環境安全，開發以植物資材為主的忌避劑商品有其必要性。本研究目標在發展一種快速篩檢方法來篩選對貓蚤 (Ctenocephalides felis) 具有忌避功效的植物性精油，其方法為將兩條同樣尺寸的濾紙條 (長 9 cm，寬 0.7 cm) 分別滴上待測物及酒精，待乾燥後，再將兩條濾紙的長邊以雙面膠帶黏合，而形成一濾紙條，然後置入放有 30 隻未吸血貓蚤的圓底長玻璃試管中 (長 25 cm、直徑 1.4 cm)，靜置 30 分鐘後，記錄貓蚤在每一濾紙條半邊分布情況，並計算其忌避率。結果顯示，桂皮醛型土肉桂 (Cinnamomum osmophloeum, cinnamaldehyde type) 葉子精油在使用濃度為 2%、1% 及 0.5% 時，對貓蚤顯現的忌避效果分別為 97.5%、97.7%及73.3%，其主成分trans-cinnamaldehyde 2% 濃度對貓蚤的忌避率為 97.6%；臺灣杉 (Taiwania cryptomerioides) 心材精油在使用濃度為 2% 的忌避效果為 89.6%；左手香 (Plectranthus amboinicus) 葉子精油在使用濃度 2% 的忌避效果為 83.8%，左手香主成分為 thymol，thymol 0.5% 濃度對貓蚤的忌避率為 90.6%。其中以濃度為 2% 之 trans-cinnamaldehyde 的忌避持續活性最為持久，晾乾8小時後還可達到95.3% 的忌避效果。貓蚤吸血後的試驗結果顯示，0.5% thymol 與 2% trans-cinnamaldehyde 對於吸血 24 小時的貓蚤都有相當高的忌避率。另外在比較以 diblock copolymers 包埋主成分的溶液忌避效果測試中，trans-cinnamaldehyde溶液對於貓蚤成蟲的忌避效果都高於 thymol溶液；且在持續性測試上，包埋的比未包埋的 2% trans-cinnamaldehyde 溶液對於貓蚤成蟲的忌避效果來得更持久。

Flea bites not only cause nuisance to humans and pets but also transmit diseases such as plague. Insect repellent is commonly recommended for personal protection in areas where fleas are present. Although synthetic repellents remain prevailing on the market, the development of plant material as flea repellents is increasingly important when considering human health and environmental safety. This study therefore aims to study the activity of numerous plant-based flea repellents by using an improved technique that speeds up the screen of repellents. Two pieces of long-stripped filter paper with the same size (0.7 by 9 cm) were impregnated with test compound and vehicle, respectively. After drying, the two filter papers were glued along the long side and inserted into the glass test tube (1.4 cm diameter, 25 cm long) where harbor 30 non-blood-fed cat fleas (Ctenocephalides felis). The distribution of cat fleas in each side of the filter paper was recorded after 30 min for the indication of repellency. The results showed that leaf essential oil of Cinnamomum osmophloeum (cinnamaldehyde type) exhibits 97.5%, 97.7% and 73.3% repellent activity against cat fleas when the concentration is 2%, 1% and 0.5%, respectively. Also, the trans-cinnamaldehyde, a main component of leaf essential oil of Cinnamomum osmophloeum, displays 97.6% repellent activity when the concentration is 2%. The heartwood essential oil of Taiwania cryptomerioides exhibits 89.6% repellent activity against cat fleas when the concentration is 2%. The leaf essential oil of Plectranthus amboinicus exhibits 83.8% repellent activity against cat fleas when the concentration is 2%, and the main component of which, thymol, displays 90.6% repellent activity against cat fleas when concentration is 0.5%. Particularly, the repellent activity of 2% trans-cinnamaldehyde remains its repellency property (up to 95.3%) even after 8 hours. Furthermore, the fed cat fleas were highly repelled by 0.5% of thymol and 2% of trans-cinnamaldehyde. The repellent test of diblock-encapsulated main components revealed that the repellent activity of diblock solution of 2% trans-cinnamaldehyde against adult cat fleas is higher and more stable than thymol. Moreover, the diblock solution of 2% trans-cinnamaldehyde exhibits better and longer repellent activity than un-encapsulated 2% trans-cinnamaldehyde.