Allelopathy of Velvetbean: Determination and Identification of L-DOPA as a Candidate of Allelopathic Substances
) was found to be the most promising candidate. It is recognized that this tropical legume grown for green manure, has a special ability to smother weeds. The field test showed that test plots containing velvetbean had the smallest weed population compared to that of tomato, egg plant, upland rice, and fallow conditions. HPLC and seed germination and seedling growth bioassays showed that the growth inhibiting substance was L-3,4-dihydroxyphenylalanine (L-DOPA). L-DOPA is a well known precursor of the neurotransmitter dopamine and is an intermediate of many alkaloids. This study revealed that velvetbean leaves and roots contain large amounts of L-DOPA (about 1% of the fresh weight). L-DOPA suppressed the growth of some broad leaf weeds, while little effect was observed on grasses. It was concluded that in addition to its usefulness as a green manure, velvetbean could be utilized as an allelopathic crop to control weeds.