Chemical compositions and biological properties of the leaf essential oil of three <i>Melaleuca</i> species

The genus Melaleuca (Myrtaceae) is a valuable plant resource for research and applications in medicine, pharmacy, the pharmaceutical industry and folklore medicine.The present study aimed to investigate the chemical components and biological properties of the essential oils (EOs) of three Melaleuca species.Gas chromatography-mass spectrometry analyses revealed that the EOs extracted from the leaves of M. cajuputi, M. quinquenervia and M. leucadendra contained 19-21 compounds with high amounts of oxygenated monoterpenes and sesquiterpenes.Subsequent bioassays demonstrated that the EOs of M. cajuputi, M. quinquenervia and M. leucadendra exhibited antimicrobial activity against all tested microorganisms, including Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aegurinosa and Candida albicans, with minimum inhibitory concentrations in the range 640-2,560 g/ml.The same EOs exerted inhibitory effects against -amylase, -glucosidase, acetylcholinesterase and xanthine oxidase with IC 50 values ranging from 331.920.64 to 1,45393.79g/ml.The findings obtained in the present study provide additional insight into the enzyme inhibitory properties of the leaf EOs from Melaleuca species that have not been reported in previous research, at least to the best of our knowledge.Melaleuca alternifolia, Melaleuca cajuputi, Melaleuca leucadendra and Melaleuca quinquenervia (1).According to traditional Vietnamese medicine, the species M. cajuputi, M. leucadendra and M. quinquenervia are widely used in the treatment of diseases, such as cold, flu, fever, malaria, indigestion, bone pain, diarrhea, inflammatory skin diseases, allergies and eczema (2).Previous studies on the chemical constituents of the plant EOs have demonstrated that the EOs of M. cajuputi are mainly composed of 1,8-cineol, -pinene, -terpinene, p-cymene, -terpineol, caryophyllene, -humulene and -gurjunene (3-6).The EOs of M. leucadendra L. have been found to be mainly composed of p-cymene, -terpinene, -terpinene, 4-terpineol, caryophyllene, methyleugenol and E-nerolidol (7-10).The main components of the EOs of M. quinquenervia have been shown to be monoterpenes (1,8-cineole, -pinene, -terpineol, limonene) and sesquiterpene (viridiflorol, E-nerolidol) (11,12).Furthermore, pharmacological studies on the EOs from M. cajuputi, M. quinquenervia and M. leucadendra have demonstrated their antibacterial, antimycrobacterial, antivirus, antifungal, antiinsecticidal and antioxidant effects (4,6,9,10,(13)(14)(15)(16)(17)(18); however, other investigations have revealed that the chemical compositions of EOs of M. cajuputi, M. quinquenervia and M. leucadendra vary extensively in different geographic and ecological conditions, even from different regions of the same country, resulting in several chemotypes (7,9,10,12,(18)(19)(20).In addition, studies on the biological activities of EOs from M. cajuputi, M. quinquenervia and M. leucadendra species grown in Vietnam are still limited and primarily focus on the EOs from M. cajuputi (4,6,14,18).