Influence of Different Drying Methods on Extraction Yield, Chemical Compositions, Total Phenolic and Flavonoid Contents and Antioxidant Activity of Essential Oil from Aerial Parts of Ferulago angulata Boiss.

Drying is one of the most common and effective techniques for maintaining the quantitative and qualitative characteristics of medicinal plants in the postharvest stage. Thus, in the current study, the effect of different drying methods including shade drying (SD), hot air (HAD; 40 and 60 ºC) and freeze drying (FD) on the extraction yield, chemical compositions, total phenolic and flavonoid content and antioxidant activity of essential oil from aerial parts of Ferulago angulata was investigated. The results revealed that the drying method has a significant effect on the studied properties. The lowest (0.89%v/w) and the highest essential oil extraction yield (2.5%v/w) were obtained for SD and FD aerial parts of F. angulata, respectively. The identified chemical compounds using gas chromatography-mass spectrometry represented 74.74-96.97% of the essential oil. Cyclofenchene (15.02-21.65%), Trans-ß-Ocimene (14.90-20.10%), O-Cymene (4.48-8.88%), Bornyl acetate (4.57-7.94%), ß-Myrcene (2.84-3.75%), ɣ-Terpinene (2.77-4.61%), Trans-Verbenol (2.15-3.29%), Limonene (2.15-2.92%),  β-Pinene (1.55-2.58%) and Germacra-D (1.38-3.46%) were the main chemical constituents of the SD, HAD and FD aerial parts of F. angulata essential oil. FD preserves the maximum chemical constituents and increasing temperature in HAD reduces the amount of chemical constituents of the essential oil. Total phenolic content of essential oil from FD (188 ± 0.23 mg GAE/g), HAD 40°C (185± 0.31 mg GAE/g), HAD 60ºC (169.56 ±0.26 mg GAE/g) and SD (167.03± 0.19 mg GAE/g) were almost more than twice the total flavonoid content. The highest scavenging activity of DPPH· and ABTS· based on IC50 were obtained for FD sample and were equal to 5.614±0.25 and 3.368±0.62 mg/mL, respectively. In addition, the FRAP of essential oil from FD aerial parts of F. angulata was obtained in the range of 5.923-11.074 mM FeSO4.7H20. Finally, it can be concluded that FD could be a suitable method for drying aerial parts of F. angulata.