Phytochemicals and Bioactivities of Australian Native Lemon Myrtle ( Backhousia citriodora ) and Lemon-Scented Tea Tree ( Leptospermum petersonii ): A Comprehensive Review

Through growing and weather conditions, Australian native herbs possess unique taste, flavour, and phytochemical content with wide bioactivity. Lemon myrtle and lemon-scented tea tree are Australian native herbs with a characteristic lemon flavour. The sensory and bioactive properties of herbs are influenced through a number of processes from harvest to use. Their cost effective processing and preparation while maintaining maximum sensory attributes and phytochemicals with the highest bioactivities are a priority towards determining their use. The review summarizes the recent research on the retention of polyphenols during pre-treatment or processing, various extraction parameters, extraction, bioactivities, isolation, and preparation or encapsulation. The limitations in existing research and direction for future research are also highlighted in this review. In general, the retention of polyphenols, antioxidant properties, and essential oil in lemon myrtle and lemon-scented tea tree leaves is significantly influenced by drying approaches, conditions, and pre-treatments. The extraction yield and stability of polyphenols and their various bioactivities including antioxidant, antimicrobial, anti-inflammatory can be varied with extraction solvent, applied method, and encapsulation operating conditions. Overall, further research is required in identification, isolation, and purification of individual bioactive compounds using sophisticated approaches. Finally, improvement in the overall process to a simple, cost-effective, and efficient one will benefit the end products and ultimately the native food industry, pharmaceuticals, and cosmetic industries.