<i>p</i>‐Hydroxybenzoic Acid, a Growth Regulator, Isolated from Woody Cuttings of <i>Ribes rubrum</i>

Abstract

Abstract Woody cuttings of Ribes rubrum , an easy plant to root, were extracted with methanol. One fraction of this extract was both water and ether soluble; a part of it was only water soluble. From the water and ether soluble fraction a crystalline compound was isolated which was fully identified with p ‐hydroxybenzoic acid (PHB) by m.p., mixed m.p., infrared spectrum, ultraviolet absorption in neutral and alkaline methanol and chemical analyses. For Avena coleoptiles straight growth test, p ‐hydroxyhenzoic acid was found to have a significant growth promoting activity in the range 20–100 μg/ml. and it showed strong growth inhibition at concentrations higher than 200 μg/ml. From the same extract fraction a phenolic ester was isolated by paper chromatography which showed a weak growth inhibiting activity. This compound was identified as an ester of p ‐hydroxybenzoic acid by micro‐scale reactions. From the extract soluble only in water further amounts of crystalline p ‐hydroxybenzoic acid were obtained by alkaline hydrolysis. This PHB may have arisen from the breakdown of pelargonidin glucosides.