Changes in valerenic acids content of valerian root (Valeriana officinalis L. s.l.) during long-term storage

Dried valerian (Valeriana officinalis) root powder was stored at 5, 14 and 30 °C under low, moderate and high humidity conditions for 6 months, and the level of the valerenic acids monitored on a monthly basis. From an initial moisture content of 5 g/kg, the moisture level during storage decreased in root powder stored at low humidity and increased during storage at high humidity, with the effect greatest at 30 °C.The concentration of valerenic acid significantly decreased over time and was affected by temperature and humidity with the loss greatest at 30 °C in low humidity. Acetoxyvalerenic acid also decreased over time but with greatest loss at 30 °C and high humidity. Hydroxyvalerenic acid was not detected in the fresh sample but was present in all stored samples and tended to reflect the decrease in acetoxyvalerenic acid. The concentration of total valerenic acids essentially mirrored the change in valerenic acid.It is concluded that maximum retention of valerenic acids would be achieved by storing valerian at a temperature lower than about 14 °C with humidity not a great concern. If storage is to occur at higher temperatures, retention of valerenic acids is favoured by storage under a high humidity but such a recommendation is not considered practical due to the risk of microbial growth and increasing difficulty of postharvest handling of moist material.