Rapid alternative of the post-harvest process to enhance the irones content in Iris germanica L

Abstract

Postharvest has vital impact on production of desired compounds in some medicinal plants. Iris germanica L. rhizome with the trade name of orris root, should be kept for 3–5 years, to produce irones from triterpene iridals. Irones have an important role in food, pharmaceutical and perfumery industries. Here, we evaluated the effect of rhizome type (whole and sliced) and drying methods including infrared, microwave, oven, vacuum-oven, shade and sun drying on volatile constituents of orris root, especially on irone content. The effect of these treatments on drying time (DT), phytochemical and antioxidant capacity of orris root has been also investigated. Rhizome type and drying methods significantly affect on DT (P < 0.01). Lowest DT was in Microwave and whole rhizome with 1:4 $\acute{1}$:4 $5^{″}$ and the highest DT was observed in shade and whole rhizome with 4704:0 $\acute{0}$:0 $0^{″}$. Interestingly, microwave drying not only reduced the time of drying but also, increased the irones content compared to the fresh samples. The negligible amount of cis-α-irone and cis-γ-irone in fresh sample (0.2 %), reached to more than 90 % in whole rhizome by microwave drying. In almost all methods, irone content was significantly higher in whole rhizome rather than the sliced rhizomes. However, the highest TPC (110.29 mg GAE/g DWP), TFC (70.344 mg QUE/g DWP) and antioxidant activity (DPPH: 104.988 mg TBHQ/g DWP) was observed in sun dried whole sample. In conclusion, microwave is the best method for producing irone compounds and sun drying could be the best method to keep the phenolic and antioxidant compounds in I. germanica.