Herbicidal Activity of Isolated Fractions and Identified Compounds from the Ethyl Acetate Extract of Parthenium hysterophorus L. Leaves on Echinochloa colona (L.) Link and Hedyotis verticillata (L.) Lam.

Abstract

Ethyl acetate extract of Parthenium hysterophorus leaves was fractionated through vacuum liquid chromatography resulting in nine main fractions which were tested against germination, plumule, and radicle lengths of Echinochloa colona and Hedyotis verticillata. Fractions 5 and 6 completely inhibited the germination of the bioassay weeds. The presence of five major bioactive compounds [stigmasterol (ST), ursodeoxycholic acid (UDCA), naphthalene (NAP), bis (2-ethylhexyl) adipate (DEHA) and bis (2-ethylhexyl) phthalate (DEHP)] was confirmed through GC-MS in these fractions. Dose-response studies were carried out at 0.5, 1.0, 1.5 and 2.0 mg/ml and 0.5, 1.0, 1.5 and 2.0 kg a.i./ha in the laboratory and greenhouse, respectively. In the laboratory experiments, DEHA and DEHP exhibited potent inhibition on germination (P<0.05) of E. colona and H. verticillata by 82-86 and 83-91%, respectively, at the highest concentration of 2.0 mg/ml. All the five compounds inhibited seed germination ranging from 61-73% for E. colona and 35-40% for H. verticillata under greenhouse. Plumule length of H. verticillata was strongly suppressed at 2.0 mg/ml of UDCA with 80% inhibition under laboratory, while 57% inhibition was obtained under greenhouse at 2.0 kg a.i./ha. Similarly, radicle length was suppressed with >90% on both the species under laboratory by UDCA. However, in the greenhouse UDCA was more phytotoxic to E. colona with a 72% reduction in radicle length as compared to H. verticillata with 42% radicle retardation. The present study revealed that DEHP, DEHA and UDCA could be potential sources of natural herbicide.