Drying methods and distillation time affects essential oil content and chemical compositions of Acorus calamus L. in the western Himalayas

• Standardization of drying methods and distillation time for Acorus calamus.
• Drying rhizomes in oven at 40 °C for 60 h produced good quality oil.
• Distillation of rhizomes for 24 h significantly increased essential oil content.
• Increase in distillation time decreased concentration of low boiling point essential oil constituents.

Experiments were conducted to study the effect of drying methods and distillation time on essential oil content and composition of Acorus calamus L. rhizomes under western Himalaya during 2013–2014. In the first experiment, the effect of different drying methods (sun drying, shade drying, oven drying at 40 °C for 60 h and 70 °C for 24 h) on essential oil content and composition of vacha (Acorus calamus) rhizomes was studied. Volatile oil content and composition of dried rhizomes were determined by Clevenger type apparatus and GC–MS method, respectively. Drying the rhizomes under sun recorded significantly higher essential oil content (3.3 ± 0.0%) as compared to other methods. However, β-asarone (53.9 ± 0.1%) which is not desired in higher concentration was low in oven dried rhizomes at 40 °C for 60 h as compared to rhizomes of other drying methods. In second experiment, the effect of distillation time (6 h, 12 h, 18 h and 24 h) was studied. Analysis of data revealed that the essential oil increased significantly with distillation time up to 24 h. Concentration of low boiling point essential oil constituents viz., linalool, bornylene decreased with increase in distillation time but trend reversed for high boiling point constituents viz., β-asarone and acorone. Thus drying of rhizomes in oven at 40 °C for 60 h and distillation of dried rhizomes for 24 h maintained the quality of essential oil.