Volatile and Non-Volatile Content Determination and Biological Activity Evaluation of Fresh Humulus lupulus L. (cv. Chinook) Leaves and Inflorescences

Abstract

In this work, the fresh leaves and inflorescences of Humulus lupulus L. cv. Chinook hops were investigated in order to describe their chemical composition and evaluate their biological activities. The analyses were carried out first on fresh untreated samples and then on pulverized ones using the SPME-GC-MS technique. In total, forty-two molecules belonging to different chemical classes were identified, and among these, twenty-three were terpene compounds. In order to carry out the activity assays, the powders were subjected to extraction with two different solvents (methanol and distilled water) by stirring and subsequent sonication at room temperature. To chemically characterize the extracts, the methanolic ones were analyzed by direct injection into the GC-MS apparatus, while the aqueous ones were analyzed by DI-SPME-GC-MS. In addition, with the aim to obtain information on the non-volatile content of the methanolic extracts, they were also subjected to derivatization, and the silylated derivatives were analyzed by GC-MS. The antioxidant activity was then evaluated by means of DPPH and ABTS assays after the determination of the total content of polyphenols and flavonoids. The greatest effects were observed on the methanolic extracts rather than on the aqueous ones. Furthermore, a preliminary study on the cytotoxic power of the methanolic extracts was also conducted on three different human cancer cell lines, such as non-small cell lung cancer (H1299), melanoma (A375) and breast cancer (MCF7). The obtained results showed that the two extracts induced a marginal effect on reducing breast tumor, melanoma and non-small cell lung cancer cell proliferation.