Investigating the chemical composition of Humulus lupulus plant flowers has been localized

Abstract

Introduction: Humulus lupulus from the Canabinaceae family is native to Europe, the Middle East and East Asia. Chemical compounds of hops are generally classified in 4 main categories including resins, bitter acids, essential oils (terpenoids) and polyphenols. Objectives: The objective of this study was investigating the chemical composition of vernalized H. lupulus flowers. Method: Extraction was done by maceration method using petroleum ether, dichloromethane and methanol solvents. Methanol extract was further partitioned by solvent extraction method using ethyl acetate and n-butanol. Dried n-butanol fraction of the methanol extract was extra fractionated using Sep-Pak cartridge (C18) and increasing ratio of methanol:water mixtures. Isolation and purification of the compounds fulfilled via reversed-phase preparative HPLC that led to isolation of 2 compounds. Structure elucidation was ascertained using spectroscopic method (NMR 1H, 13C and On-Line UV spectra). The essential oils from the two samples of vernalized and wild Hops were achieved through hydrodistillation and analyzed via GC-MS. The antioxidant properties of methanol extract and essential oil were measured by DPPH method. Results: Phytochemical study of hops vernalized methanol extract yielded two glycosylated flavonoids (7-O-Beta-Glucoside-4'-O-Rhamnosyl-Kaempferol and 3,7-Dirhamnosyl-Kaempferol). The analysis of the wild and vernalized H. lupulus essential oils led to the identification of wild species (46) and vernalized species (57) compounds. Besides, methanol extract showed antioxidant activity with RC50=93/62 ug/ml. Conclusion: The phytochemical study of vernalized H. lupulus revealed presence of flavonoids the methanol extract also showed outstanding antioxidant activity. The analysis of essential oils showed most of which consisted of sesquiterpene hydrocarbons (β-Caryophyllene) and oxygenated sesquiterpene (β-Bisabolol) for the wild species and oxygenated sesquiterpenes (β-Bisabolol) and sesquiterpene hydrocarbons (β-Sesquiphellandrene) for vernalized species