effect of harvest time and root diameter on glycyrrhizin content in glycyrrhiza glabra

licorice, glycyrrhiza glabra (fabaceae), is one of the herbal medicines. glycyrrhizin is the importance content through compounds exiting in licorice, which is 50 times sweeter than sucrose. glycyrrhizin used as the primary matter in pharmacy and used to remedy of many diseases, and also, used in tobacco, confectionary and beverage industries. since glycyrrhizin in the phases of growth received at maximum and then decreased; and also to consider of root diameter and harvest time effect on active substance content, this study done for determine the best harvest time and suitable root diameter to obtain the greatest glycyrrhizin in this plant. for this study, root of glycyrrhiza glabra were collected in four times (nov, dec, jan and feb) and in three root diameter (2 cm) from gorgan (araghi mahalle agricultural station). variant of measurement in this study were including fresh weight, dry weight (for determination of percentage of humidity) and glycyrrhizin content. extraction of glycyrrhizin was done with methanol and its measurement done with used hight performance liquid chromatography (hplc). the result showed that the least root diameter were containing the least humidity percentage (32.46%) and the greatest of glycyrrhizin (1.187%), the root were harvested in jan., in comparison with other harvest time, were containing the least humidity percentage (22.26%) and the greatest amount of glycyrrhizin (1.112%).