Melaleuca

Abstract: Essential oil of Melaleuca alternifolia was tested for antiviral activity against Tobacco Mosaic Virus When applied to plants of Nicotiana glutinosa as a pre-inoculation spray at 100, 250 and 500 ppm, the oil was effective in significantly decreasing lesion numbers for at least 10 days post inoculation

Abstract: Plants belonging to Melaleuca genus (Myrtaceae family) are native to Oceania, where they have been used for ages by Aborigine people in Australian traditional medicine, mainly because of their broad-spectrum antimicrobial activity. Although, M. linariifolia, M. dissitiflora, and other species of Melaleuca can also be used, the tea tree oil, an essential oil obtained from M. alternifolia shows the longest history of medicinal uses. Tea tree oil contains for the 80-90% several monoterpenes (terpinen-4-ol, α-terpinene, 1,8-cineol, p-cymene, α-terpineol, α-pinene, terpinolene, limonene, and sabinene). Sesquiterpenes and aromatic compounds further compose this oil. The essential oil of Melaleuca spp. has been reported to possess effective antibacterial and antifungal properties in vitro. In particular, data show that 1,8-cineol, terpinen-4-ol and methyl eugenol play the key role in mediating this oil's antimicrobial activity. Copyright © 2017 John Wiley & Sons, Ltd.

Abstract: Three different species of Myrtaceae growing in Australia and New Zealand are known as 'Tea-tree': the Australian Tea tree (Melaleuca alternifolia), the New Zealand Manuka (Leptospermum scoparium) and Kanuka (Kunzea ericoides). All three essential oils are used by aromatherapists, although only Melaleuca has been tested for toxicity, and its antimicrobial effects studied. The pharmacology and antimicrobial activity of the three 'tea-tree' oils was determined using guinea-pig ileum, skeletal muscle (chick biventer muscle and the rat phrenic nerve diaphragm) and also rat uterus in vitro. Differences were shown between the three essential oils in their action on smooth muscle: Manuka had a spasmolytic action, while Kanuka and Melaleuca had an initial spasmogenic action. Using the diaphragm, Manuka and Melaleuca decreased the tension and caused a delayed contracture; Kanuka had no activity at the same concentration. The action on chick biventer muscle was, however, similar for all three oils, as was the action on the uterus, where they caused a decrease in the force of the spontaneous contractions. The latter action suggests caution in the use of these essential oils during childbirth, as cessation of contractions could put the baby, and mother, at risk. The comparative antimicrobial activity showed greater differences between different samples of Manuka and Kanuka than Melaleuca samples. The antifungal activity of Kanuka was inversely proportional to its strong antibacterial activity, whilst Manuka displayed a stronger antifungal effect, though not as potent as Melaleuca. The antioxidant activity of Manuka samples was more consistent than that of Kanuka, while Melaleuca showed no activity. The variability in the Manuka and Kanuka essential oils suggests caution in their usage, as does the fact that the oils have not been tested for toxicity.

Abstract: In vitro antifungal activity of the essential oils from Monarda citriodora and Melaleuca alternifolia was evaluated on 15 common post-harvest pathogens of a variety of crops. Both oils exhibited a high level of antifungal activity both by direct contact and in the vapor phase. Oil from Monarda citriodora was generally more active than that from Melaleuca alternifolia, particularly against more rapidly growing fungal species.