Flavonoids of <i>Solanum rostratum</i> seeds: identification and plant growth regulatory activity evaluation

For the first time, five flavonoids (1 ∼ 5) were separated and characterised from seeds of the invasive <i>Solanum rostratum</i> Dunal. Through the analysis of spectroscopic data and comparison with published literature, the structures of these substances were ascertained. These flavonoids were apigenin (<b>1</b>), quercetin (<b>2</b>), kaempferol-3-<i>O</i>-β-d-glucopyranoside (<b>3</b>), quercetin-3-<i>O</i>-β-d-glucopyranoside (<b>4</b>) and acacetin-7-<i>O</i>-[glucopyranosyl-(1→6)]-β-d-glucopyranoside (<b>5</b>). Their plant growth regulatory activity was assessed using ryegrass (<i>Lolium perenne</i>) as the receiver species, which were all found to possess stimulatory activity. Among them, quercetin-3-<i>O</i>-β-d-glucopyranoside (<b>4</b>) exhibited the maximum promotive effect on ryegrass, at the concentration of 500 μg/mL, it enhanced shoot growth by 117%. Our study reveals that flavonoids in <i>S. rostratum</i> seeds have growth promotive effect, which might contribute to its invasion success by stimulating seed germination and seedling growth; meanwhile, our results also implies that these flavonoids might be developed into growth promoting compounds applicable in agricultural practices.