Effects of Tropical Citrus Essential Oils on Growth, Aflatoxin Production, and Ultrastructure Alterations of Aspergillus flavus and Aspergillus parasiticus
- 650 Downloads
Ethyl acetate extracts and hydrodistillated essential oils from five cultivars of tropical citrus epicarps were evaluated for their inhibitory activities against Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, Aspergillus parasiticus, and Penicillium sp. using disk diffusion and broth microdilution assays. Essential oils prepared from kaffir lime (Citrus hystrix DC) and acid lime (Citrus aurantifolia Swingle) epicarps exhibited stronger antifungal activity to all fungi than their ethyl acetate extracts with minimum inhibitory concentration and minimum fungicidal concentration values of 0.56 and 1.13 mg/ml (dry matter), respectively, against aflatoxin-producing A. flavus and A. parasiticus. The dominant components of the essential oil from kaffir lime were limonene, citronellol, linalool, o-cymene, and camphene, whereas limonene and p-cymene were major components of acid lime essential oil. Pure limonene, citronellal, and citronellol were five to six times less fungicidal than the natural essential oils, indicating the synergistic activity of many active compounds present in the oils. Kaffir and acid lime essential oils significantly reduced aflatoxin production of A. flavus and A. parasiticus, particularly lime essential oil, which completely inhibited growth and aflatoxin production of A. flavus at the concentration of 2.25 mg/ml. Target cell damage caused by acid lime essential oil was investigated under transmission electron microscopy. Destructive alterations of plasma and nucleus membrane, loss of cytoplasm, vacuole fusion, and detachment of fibrillar layer were clearly exhibited in essential-oil-treated cells.
KeywordsCitrus essential oils Aspergillus flavus Aspergillus parasiticus Aflatoxin Antifungal TEM
This research was funded by the Graduate School and Nutraceutical and Functional Food Research and Development Center, Faculty of Agro-Industry, Prince of Songkla University. We express great appreciation to the Scientific Equipment Center, Prince of Songkla University for their electron microscopy facility and excellent TEM technical assistance.
- Agnihotri, K. V., Thappa, K. R., Meena, B., Kapahi, K. B., Saxena, K. R., Qazi, N. G., et al. (2004). Essential oil composition of aerial part of Angelica glauca growing wild in North West Himalaya (India). Phytochemistry, 652, 2400–2413.Google Scholar
- Caccioni, D. R. L., Guizzardi, M., Biondi, D. M., Renda, A., & Ruberto, G. (1998). Relationship between volatile components of citrus fruit essential oils and antimicrobial action on Penicillium digitatum and Penicillium italicum. International Journal of Food Microbiology, 43, 73–79.CrossRefGoogle Scholar
- Chaisawadi, S., Thongbute, D., Methawiriyaslip, W., Pitakworarat, N., Chaisawadi, A., Jaturonrasamee, K., et al. (2003). Preliminary study of antimicrobial activities on medicinal herbs of Thai food ingredients: Abstract. Acta Horticulturae, 675, 111–114.Google Scholar
- Chathaphon, S., Chantachum, S., & Hongpattarakere, T. (2008). Antimicrobial activities of essential oils and crude extracts from tropical Citrus spp. against food-related microorganisms. Songklanakarin Journal Science and Technology, 30, 125–131.Google Scholar
- Chinaphuti, A., Trikarunasawat, C., Wongurai, A., & Kosotcharoenkul, S. (2002). Production of in-house ELISA test kit for detection of aflatoxin in agricultural commodities and their validations. Kasetsart Journal (Natural Science), 36, 179–186.Google Scholar
- National Committee for Clinical Laboratory Standards. (2002). Reference method for broth dilution antifungal susceptibility testing of filamentous fungi; approved standard. NCCLS document M38-A. Wayne: NCCLS, [ISBN 1-56238-470-8].Google Scholar
- Reddy, C. S., Reddy, K. R. N., Raja Kumar, N., Laha, G. S., & Muralidharan, K. (2004). Exploration of aflatoxin contamination and its management in rice. Journal of Mycology and Plant Pathology, 34, 816–920.Google Scholar
- Saikia, D., Khanuja, S.P.S., Kahol, A.P., Gupta, S.C., & Kumar, S. (2001). Comparative antifungal activity of essential oils and constituents from three distinct genotype of Cymbopogen spp. Current Science, 80, 1264–1266.Google Scholar