2-Methoxystypandrone, a potent phytotoxic substance in Rumex maritimus L

Herbicide use has raised concerns which results in the need to find an alternative approach, using natural methods, of controlling weeds. Phytotoxic substances released from plants have been used to manage weeds biologically. Rumex maritimus, belonging to the Polygonaceae family, is well known to have a wide range of biological properties. However, the phytotoxic properties of R. maritimus is not well documented. Thus, we conducted an investigation into the phytotoxic potential of R. maritimus and attempted to find out its phytotoxic substances. Leaf, stem and root extracts of R. maritimus exhibited a strong inhibitory effects on root and shoot length of Lactuca sativa L., Medicago sativa L., Lolium multiflorum Lam., Phleum pratense L. With increasing extract concentration, inhibition increased. One substance, 2-methoxystypandrone, was purified after a series of chromatography and characterized by spectral data. 2-Methoxystypandrone reduced the seedling length of Lepidium sativum at concentration ≥ 3 μM. The required 50% growth inhibition concentration of Lepidium sativum seedling for 2-methoxystypandrone was ranged 5.8–11.8 μM. Therefore, it is suggested that the phytotoxic effects of R. maritimus on the test plants may be caused due to the presence of 2-methoxystypandrone.