p-hydroxybenzaldehyde, a growth inhibitory chemical extracted from common nandina (Nandina domestica Thunb.) leaf

Phytotoxicity of active substances in common nandina (Nandina domestica Thunb.) was investigated. Bioassays were conducted using several weeds [(redroot amaranth (Amaranthus retroflexus L.), Abutilon theophrasti Medic. and barnyardgrass (Echinochloa crusgalli (L.) Beauv.)] and crops [(lettuce (Lactuca sativa L.), cucumber (Cucumis sativus L.) and wheat (Triticum aestivum L.)] as receptor plants by the method of grinded plant tissue powder mixed with agar (PPA). The inhibitory effects of leaf powders of common nandina at 10 g·L⁻¹ concentration on the seedling growth of lettuce were more pronounced than other plant parts. According to the EC50 values of common nandina leaf powder on the different receptor plants, dicotyledon plants of redroot amaranth, lettuce, A. theophrasti and cucumber showed higher susceptibility than monocotyledon plants of wheat and barnyardgrass, with redroot amaranth showing the highest susceptibility. The common nandina leaves may possess phytotoxic potential and active substance. The methanol extract of its leaves was purified and one growth inhibitory substance was isolated and identified as p-hydroxybenzaldehyde by its ¹H-NMR, ¹³C-NMR and EI-MS spectral data. The seedling growth of lettuce and redroot amaranth were strongly inhibited at 0.125 g·L⁻¹ and the roots died at 0.500 g·L⁻¹ concentrations. It suggested that p-hydroxybenzaldehyde may contribute to the phytotoxicity of common nandina.