Influence of seasonal variation on the chemical composition of Piper amalago essential oils and their phytocytogenotoxic activity in model plants and weeds

ABSTRACT

The essential oil of Piper amalago L. is recognized for its bioactive compounds with phytotoxic potential against invasive plants. However, little is known about the role of seasonal variation in the action of these compounds. This study aimed to investigate the impact of dry and rainy seasons on the chemical composition, phytotoxic, and cytogenotoxic activity of P. amalago essential oil. Analysis of the chemical composition revealed qualitative and quantitative variations, highlighting β-elemene, germacrene A, linalool, and β-caryophyllene as major compounds. The essential oil from the rainy season showed higher yield compared to that of the dry season. In pre-emergence tests against Bidens pilosa (invasive plant) and Lactuca sativa (non-target plant), negative effects on germination and root and shoot growth were observed, with these effects being more pronounced at higher concentrations, resembling the herbicide glyphosate. The essential oil from the dry season exhibited greater phytotoxic activity on the germination and development of the aerial part of B. pilosa, associated with higher concentrations of linalool and caryophyllene oxide. Additionally, the essential oils of P. amalago induced changes in the mitotic index and aneugenic alterations in L. sativa meristematic cells. These results underscore the bioherbicidal potential of P. amalago essential oil, highlighting its greater efficacy against B. pilosa during the dry season, possibly due to higher levels of linalool and caryophyllene oxide.

Key words
natural herbicide; weeds; cellular cycle; bioassays