In vitro herbicide activity of crude and fractionated leaf extracts of Blepharocalyx salicifolius (Myrtaceae)

The excessive use of synthetic herbicides is harmful to natural and managed ecosystems. In order to solve this issue, the search for natural compounds with lower toxicity to the environment has been intensified. This study aimed (a) to evaluate the phytotoxic activity of leaf extracts of Blepharocalyx salicifolius by taking into account the elongation of wheat coleoptile as well as of the crude ethyl acetate extract on the germination and growth of two weeds; (b) to fractionate the ethyl acetate extract; and (c) to test the phytotoxicity of fractions on etiolated wheat coleoptile. Hexane, ethyl acetate, and aqueous crude extracts were obtained through extraction with organic solvents. We used the column chromatography to fractionate the ethyl acetate extract, which resulted in 11 ethylic acetate fractions (Fr1-Fr11). The bioassays of wheat coleoptile elongation, germination, and seedling growth of guinea grass as well as the morning glory showed that the ethyl acetate extract possessed pronounced phytotoxic potential to inhibit the elongation of wheat coleoptile at all tested concentrations. In addition to this, the extract changed the mean germination time of guinea grass seeds and inhibited the growth of shoots and roots of both weeds, the fact that caused anomalies, such as necrosis and severe atrophy. Furthermore, we identified that Fr5 and Fr6 are the most promising ethyl acetate fractions. Thus, this study presents that the ethyl acetate extract of mature leaves of B. salicifolius has potential to produce natural herbicides and that the main phytotoxins are present in the Fr5 and Fr6 fractions, thereby offering scope for further studies. (AU)