An examination of the anti-bacterial, anti-fungal and anti-Giardial properties of macadamia nut
Macadamia integriflora (family Proteaceae) is an endemic Australian plant that has been used for thousands of years as a food. Its nuts are known to store well, raising the possibility that they may contain antimicrobial compounds and therefore may have value as a functional food, able retard food spoilage and prevent food poisoning and other food-borne diseases. M. integriflora extracts were investigated for their ability to inhibit the growth of a panel of bacteria and fungi of importance to food spoilage and food poisoning, as well as the gastro-intestinal protozoal parasite Giardia duodenalis. All extracts displayed broad spectrum antimicrobial activity, each inhibiting the growth of 7 of the 18 bacterial species tested (39%). In contrast, none of the fungal species were inhibited by these extracts. Strong inhibitory activity was detected with minimum inhibitory concentration (MIC) values as low as 8.0 µg mL-1 against some bacteria, although most measured MICs were generally several orders of magnitude higher. All extracts inhibited 54% of the Gram negative bacteria tested and none of the Gram positive bacteria. All extracts were also effective in inhibiting the gastrointestinal protozoal parasite G. duodenalis, yet were non-toxic in the Artemia franciscana bioassay. The inhibitory bioactivity against a range of microbes as well as the lack of toxicity indicates the potential for macadamia nuts in the discovery and development of new natural food preservatives and pharmaceuticals.
Desegaulx, M., Sirdaarta, J., Rayan, P., Cock, I.E. and McDonnell, P.A. (2015). An examination of the anti-bacterial, anti-fungal and anti-Giardial properties of macadamia nut. Acta Hortic. 1106, 239-246
Macadamia integriflora, antibacterial activity, Giardia duodenalis, functional food, toxicity