Toxicity of Caraway towards Bacteria Fungi Mites and Insects and its Advantages for People

Antibacterial and antifungal properties of caraway essential oil are used in therapy, but also in some other fields and may be of great importance for people.

Farag et al. (1989b) reported the inhibitory effect of six spice essential oils (including caraway) on 3 strains of Gram-negative bacteria and 4 Gram-positive bacteria. Gram-positive bacteria were more sensitive to the anti-microbial compounds in tested spices. This may be crucial for food preservation. Microbial spoilage of food is mostly inhibited by chemical food preservatives which are not fully safe for human health. Farag et al. (1989b) suggests that natural essential oils can be applied practically as antimicrobial agents which will prevent the deterioration of stored foods by bacteria and will not cause health problems to the consumer and handler.

The essential oils of several spices have strong antifungal properties and it is highly desirable to control mycotoxin formation during the storage of food. Carum carvi essential oil causes inhibition of mycelial growth and aflatoxin production of Aspergillus parasiticus. Chemicals such as potassium fluoride, acetic acid, potassium sulphite etc. also inhibit aflatoxin production but are hazardous for human health. Essential oils from spices are cheaper, natural, safe and widely used for flavouring. They can be applied as mould inhibitors to protect foods against aflatoxigenic fungi (Farag et al. 1989a).

Bang (1995) reported that several essential oils (including caraway oil) reduce significantly the infection of potato tubers by Helminthosporium solani and Rhizoctonia solani, which is important for storage.

Caraway is strongly toxic towards mites. Afifi and Hafez (1988) reported that petroleum ether, chloroform, acetone and methanol extracts of caraway fruits showed acaricidal properties towards Tyrophagusputrescentiae, which is a well known pest of stored products. The acetone extract was the most toxic one. In comparison with fenugreek (Trigonella foenum-graecuni) and lupin (Lupinus albus) caraway showed higher toxicity towards Tyrophagus putrescentiae.

Domestic mites being one of the main causes of allergy are quite a significant problem. Ottoboni et al. (1992) tested the toxicity of 10 essential oils from different plants towards the most popular house mites Dermatophagoides pteronyssinus, D. farinae, Eurogfyphus maynei, Acarus siro, Tyrophagus putrescentiae, Glycyphagus domesticus, Lepidoglyphus destructor and Gohiera fusca. From all 10 volatile oils tested, the caraway oil was among the 4 most effective ones. The authors conclude that using essential oils combined with cleaning agents could help reduce the cause of allergy in people. The strong toxicity towards mites was also proved by Watanabe et al. (1989) who tested 52 essential oils. Caraway was among the 6 most powerful ones. Isolated d-carvone showed very high activity thus being responsible for acaricidal property of caraway essential oil to a great extend.

Caraway is also toxic for some insects. Petroleum ether extract of caraway causes inhibition of larvae development in Musca domestica, Culexpipiens fatigans and mosquito (Deshmukh et al. 1987). The caraway extract has also the feeding deterrent activity in 5th-instar larvae of Spodoptera littoralis (Antonious and Hegazy 1987). These facts offer the hope for new, non-toxic to people botanical insecticides against the most popular insects and crop pests.

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