Two novel phytotoxic substances from Leucas aspera

A. K.M.Mominul Islam, Osamu Ohno, Kiyotake Suenaga, Hisashi Kato-Noguchi

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17 Citations (Scopus)


Leucas aspera (Lamiaceae), an aromatic herbaceous plant, is well known for many medicinal properties and a number of bioactive compounds against animal cells have been isolated. However, phytotoxic substances from L. aspera have not yet been documented in the literature. Therefore, current research was conducted to explore the phytotoxic properties and substances in L. aspera. Aqueous methanol extracts of L. aspera inhibited the germination and growth of garden cress (Lepidum sativum) and barnyard grass (Echinochloa crus-galli), and the inhibitory activities were concentration dependent. These results suggest that the plant may have phytotoxic substances. The extracts were then purified by several chromatographic runs. The final purification was achieved by reversed-phase HPLC to give an equilibrium (or inseparable) 3:2 mixture of two labdane type diterpenes (compounds 1 and 2). These compounds were characterized as (rel 5S,6R,8R,9R,10S,13S,15S,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (1) and (rel 5S,6R,8R,9R,10S,13S,15R,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (2) by spectroscopic analyses. A mixture of the two compounds inhibits the germination and seedling growth of garden cress and barnyard grass at concentrations greater than 30 and 3μM, respectively. The concentration required for 50% growth inhibition (I50) of the test species ranges from 31 to 80μM, which suggests that the mixture of these compounds, are responsible for the phytotoxic activity of L. aspera plant extract.

Original languageEnglish
Pages (from-to)877-883
Number of pages7
JournalJournal of Plant Physiology
Issue number11
Publication statusPublished - 2014 Jul 1


  • Bioactive compounds
  • Diterpene
  • Lamiaceae
  • Medicinal plant
  • Plant growth inhibitor

ASJC Scopus subject areas

  • Physiology
  • Agronomy and Crop Science
  • Plant Science


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