Allelopathic potential of Oldenlandia corymbosa and identification of its allelopathic substances

The use of allelopathy developed as an alternative practice for weed management in agriculture. Oldenlandia corymbosa is an annual herb and notable for being applied in folk medicine. Its diverse range of pharmacological properties and several bioactive substances have been well reported. Nevertheless, the allelopathic potential of O. corymbosa has not yet been documented. Hence, we aim to explore the allelopathy of O. corymbosa for weed control purposes. The extracts of O. corymbosa were tested to determine their effects on the seedling growth of six tested species. Significant reductions in the growth of seedling were exhibited as the plant extract concentrations increased. The plant extracts of O. corymbosa were separated in several chromatography steps; two active substances isolated and characterized as hedyotiscone A and B. Hedyotiscone A and B significantly restricted the growth of cress seedling at concentrations higher than 0.3 mM. The I₅₀ values of hedyotiscone A and B for the cress seedlings ranged from 0.023 to 0.131 mM and 0.167 to 0.810 mM, respectively. The inhibitory activity against cress seedlings indicates that hedyotiscone A and B contribute to the allelopathic effects and may be responsible for the allelopathic potential of O. corymbosa.