An overview of allelochemicals and allelopathic activity from Alpinia malaccensis

Alpinia malaccensis is a medicinal plant possesses beneficial active biological properties. This plant has been widely used to treat several diseases including diabetes, inflammatory, and oxidative stress. However, the information about its potent activity to control paddy-weeds and plant pathogens has appeared sporadically in scientific databases. Thus, this review aimed to describe the allelochemicals and allelopathy potential of A. malaccencis and its prospect for natural herbicide development. This review discussed the relevant biological activities, including antioxidant, antibacterial, fungicidal, and herbicidal properties. Based on literature studies, the predominant alellochemicals from A. malaccensis were terpenes, phenolics, flavonoids, lactones, long chain hydrocarbons, and carbocyclic acids. Of which, monoterpenoid compound such as eucalyptol, α-fenchyl acetate, thymol, and α-phellandrene, and carbocyclic acid for example methyl cinnamate were the major component in essential oil of A. malaccensis. In addition, they exhibited strong antibacterial and fungicidal activities. For antioxidant activity, phenolic and flavonoid compounds such as catechol and naringin might be responsible for its anti-free radical activity. The other important compounds isolated from A. malaccensis such as 5.6 dehydrokawain, coronarins A and E, and (E)-8(17),12-labdadiene-15,16-dial showed potent antibacterial activity. In herbicidal activity, A. malaccensis showed strong inhibition against the germination and growth of the invasive plant Merremia peltata. This report indicates that A. malaccensis is a promising source of natural allelochemicals that can be developed for natural pesticide or herbicide. However, a further experiment in the green house or paddy field were required to confirm the role of allelochemicals of A. malaccensis to control paddy-weeds and plant pathogens.