Examination of the anti-bacterial, anti-fungal and anti-Giardial properties of Macadamia nut
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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 keep well, raising the possibility that they may contain antimicrobial compounds and therefore may have value as a functional food to 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 the macadamia nut extracts. Strong inhibitory activity was detected with MIC values as low as 0.80 µg/ml against some bacteria, although most measured MIC's were generally several orders of magnitude higher than this. All extracts were more effective against Gram-negative than Gram-positive bacteria. Indeed, 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 gastro-intestinal protozoan parasite G. duodenalis, yet were nontoxic in the Artemia franciscana bioassay with LC50 values greatly in excess of 1 mg/ml. The inhibitory bioactivity against a range of microbes, as well as the lack of toxicity, indicates the potential of macadamia nuts in the discovery and development of new natural food preservatives and pharmaceuticals.
International Horticultural Conference (IHC)
Complementary and Alternative Medicine