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We investigated the potential of wild hop and determined the effects of different solvent extractions on quality and quantity of hop extracts. Three different solvents - aqueous-ethanol (75%), methanol and acetone - were applied to elicit the secondary metabolites of Humulus lupulus L. cones by automatic Soxhlet system, and extraction yield, total phenolic content, total flavonoid content and antioxidant capacity were compared. The antioxidant activity tests, DPPH, ABTS and FRAP, were used to analyze the antioxidant capacity of extracts. The crude extract obtained by aqueous-ethanol, methanol and acetone extraction were 98.65±5.2, 61.39±3.25, 69.28±4.1 mg g‑1 dry matter, respectively. The total phenolic content (TPC) as well as the total flavonoid content (TFC) of aqueous extracts exhibited the highest values. Also the antioxidant activity of extracts was different: the acetone extract had the highest value of IC(50) in the DPPH test, while the methanol extract has the highest antioxidant activity (1.79±0.25 mM Fe2+ g(‑1)) in the FRAP test, and the best result of percent inhibitors of ABTS (58.12±0.48) was observed for the aqueous-ethanol extract. In addition, ABTS value in aqueous-ethanol extract was 6.45±0.33 mmol Trolox equivalent g‑1 sample, significantly higher than others. No significant correlation was found among antioxidant measurement methods. Overall, 75% ethanol is suggested for the extraction of phenolic compounds from hop flowers due to its polarization diversity. Finally, the wild hop flowers have high antioxidant activity and a remarkable amount of phenolic compounds. They could be applied in food industries as a rich source of antioxidant activity. Characterization of the genetic diversity of wild hops is underway.

Humulus lupulus is a valuable medicinal plant that grows wild in forest areas of northern Iran. In recent decades with extension of village boundaries toward forest, hop habitat is suffering destruction. Optimization of hop micropropagation by shoot tip and nodal segments was conducted towards conservation of Iranian hop germplasm. Nodal segments were provided from the rootstock and after disinfection were established in the MS medium. After six weeks, explants grown in in vitro conditions were isolated, then were incubated in MS medium supplemented with various concentrations of plant growth regulators, including BA (0, 0.1, 0.5, 1 and 2 mg L(-1)), Kin (0, 0.1, 0.5, 1 and 2 mg L(-1)) and TDZ (0, 0.1, 0.5, 1 and 2 mg L(-1)) alone and in combination with IAA. The combination of 1 mg L(-1) BA with 0.1 mg L(-1) IAA was the best treatment applied in all traits evaluated, followed by 5.0 mg L-1 Kin and TDZ with 0.1 mg L(-1) IAA. The best treatments for shoot tip explant proliferation were the best treatments for nodal segments proliferation, except in the case of Kin, where the best results for nodal segments proliferation was observed at a concentration of 1 mg L(-1) Kin in combination with 0.1 mg L(-1) IAA. For shoot rooting, the shoots were grown in vitro; and plantlets were transferred to a rooting medium containing MS medium supplemented with different concentrations IAA (0, 0.5 and 1 mg L(-1)) and BA (0, 0.5 and 1 mg L(-1)). The highest percentage of rooting was observed in half strength MS supplemented with 1 mg L-1 IAA in combination with 1 mg L(-1) BA. Thus we recommend MS medium containing 1 mg L(-1) IAA and 1 mg L(-1) BA as a suitable micropropagation medium for industrial purposes.