Promotion of adventitious root growth by coffee extracts

Abstract

The preliminary screening results on plant growth regulation of the ethanolic extract of reasted coffee indicated that at high concentration the growth inhibition of plant seeds were observed, while at low concentration the growth promotion clearly visualized. In addition, the highest growth promotion of C. atropurpureus (55%) stimulated by the extract from roasted coffee at 100 ppm was observed while that of H. rosa-sinensis was achieved at 1000 ppm (84%). The bioassay-guided fractionation of the ethanolic extract led to the isolation of substances. Their structures were characterized by means of physical properties and spectroscopic data. The major compound was caffeine while the minor one was a mixture whose structure could not be identified. Caffeine showed the highest plant growth activity on C. atropurpureus at 100 ppm (61%) and H. rosa-sinensis at 10 ppm (81%). Plant growth regulation of plant seeds of caffeine exhibited the same the ethanolicextract. Caffeine (61%) enhanced the root growth promotions and stimulated the rooting of stem cuttings more than other compounds in roasted coffee such as chlorogenic acid (5%), theobromine (39%), theophylline (37%) and trigonelline (27%). It may be concluded that the main plant growth regulator of roasted coffee was caffeine