Effect of Harvest Time and Drying Methods on the Yield and Active Components of?Angelica dahurica

Baizhi (Angelica dahurian) has been widely used as a traditional Chinese herbal medicine, functional food and ingredient of cosmetic product, mostly because of high furanocoumarin compounds in its root. This study was designed to determine the optimal harvest stage and postharvest handling of Baizhi to obtain the highest yield and productivity. Firstly, six furanocoumarin compounds were identified in Baizhi root by liquid chromatography, including bergapten, imperatorin, isoimperatorin, xanthotoxin, oxypeucedanin and phellopterin. The first three are believed to be the active compound for skin-depigmenting by blocking the tyrosinase synthesis, whose product accelerates skin-darkening. In addition, anti-oxidation activity of Baizhi roots, which revealed by either the total phenols or DPPH radical-scavenging activity, offers another process to block skin-darkening. For their role in blocking skin-darkening, the three compounds (bergapten, imperatorin and isoimperatorin) as well as the anti-oxidation activity were analyzed to reveal the quality of Baizhi. Four postharvest drying methods, in-the-shade-, 40℃-, 70℃- and freeze-drying, were applied to analyze Baizhi roots. The results showed that in-the-shade-, 40℃- and freeze-drying did not affect the contents of imperatorin and isoimperatorin. However, bergapten content, total phenols and DPPH radical-scavenging activity were obtained more efficiently by in-the-shade- and 40℃-drying methods than the others. Freeze-drying and 40℃-drying methods were used to analyze the productivities of vegetative, bolting and summer dormancy stages. The latter is a special trait of Baizhi that occurs in summer. Both the dry weight of Baizhi roots and active compounds within decreased at bolting stage. The highest dry weight and active compounds were obtained at dormancy stage, although the anti-oxidation activity was lower than the late vegetative stage. Further analyses indicate that in Baizhi roots, cortex yields more active compounds and more anti-oxidation activity then pith does. Taken together, it is suggested to harvest the Baizhi roots at dormancy stage and subsequently handled by 40℃-drying to obtain the highest production as the ingredient of skin-depigmenting products.