Germination and Growth of the Invasive Weeds Bidens pilosa and Digitaria insularis Regulated by Novel Kaurane Diterpene Amides

Abstract

Novel kaurane ditepene monoamides were synthesized with good yields, directly from unprotected symmetrical aliphatic and aromatic diamines, hydroxylamines, dichlorophenylamines and ent-kaurenoic acid (1), using a modified protocol for monoacylation. These amides were tested against seed germination and growth of radicle and shoot of the weeds Bidens pilosa (Asteraceae), and Digitaria insularis (Poaceae). The concentrations used were 1.0 mM, 100.0, 10.0, and 1.0 mM. Propanil, the commercial herbicide, was used as internal reference. Monoamides from symmetrical aliphatic diamines were the most actives. Their log P (3.66-4.20) were closer to the value of 4.15, appropriate for herbicides. They were, in some cases, at the lower concentrations, more active  than propanil. Generally, inhibitory effects were more significant on B. pilosa than on  D. insularis. Monomide from ethylenediamine gave the best dose / response for inhibition growth of radicle and shoot  of B. pilosa, with I50  3.25 and 16.3 mM, respectively.