A Comprehensive Review of the Botany, Bioactive Compounds and Health Benefits of Leptospermum

There is increasing interest in research and application of natural bioactive compounds due to the growing demand for functional ingredients from the pharmaceutical, cosmetic and food industries. A major challenge is finding suitable natural plant resources for the development of functional ingredients. Leptospermum, a genus of the myrtle family (Myrtaceae), is primarily native to Australia. This genus has been traditionally used for the treatment of a range of ailments, such as colds, fever, constipation, diarrhoea, skin, inflammation, stomach disorder and both internal and external pain. Manuka honey, known for its medicinal properties, is produced from the nectar of Leptospermum flowers, and the leaves of some species are used for essential oil production. Various volatiles, such as pinene, citral and citronellal, have been identified in Leptospermum essential oils. In addition, various non-volatile compounds like leptosperin, cyanidin, quercetin, ellagic acid, delphinidin and myricetin have been isolated from Leptospermum extracts. Preliminary studies have linked Leptospermum essential oils and extracts with various health-promoting properties, such as antimicrobial activity, antidiabetes, anticancer and anti-Alzheimer's disease activities, revealing potential applications of Leptospermum as functional ingredients. To provide a comprehensive understanding of Leptospermum for future research and applications, this review presents an overview of its botanical features, outlines volatile and non-volatile active molecules identified in the genus, reviews potential health benefits and finally proposes trends for future studies on Leptospermum.