Hop (Humulus lupulus L.) is a perennial climbing plant cultivated for commercial use, mainly in brewing industry, since the female inflorescences (cones) contain lupulin glands that confer the characteristic bitterness, aroma and flavour to beer. However, the bioactive potential of the seeds found in these cones remains unexplored. In this study, the phenolic composition of hop seeds was analysed by LC-DAD-ESI/MS n and its antioxidant, cytotoxic and antimicrobial activities were screened against oxidizable substrates, human tumour and non-tumour cell lines, and different bacteria and fungi, respectively. (+)-Catechin and (-)-epicatechin were identified in the seeds, totalizing 17.6 ± 0.7 mg/g extract. The seed extract showed antioxidant activity mainly through the formation inhibition of thiobarbituric acid reactive substances (TBARS), and had cytotoxic effects against MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer), HeLa (cervical carcinoma), and HepG2 (hepatocellular carcinoma) tumour cells, but no toxicity towards the normal PLP2 cell line was observed. The extract showed remarkable antimicrobial properties, being better than the positive controls against almost all tested bacteria and fungi of the genus Penicillium. These results highlight the potential of hop seeds as a source of functional ingredients with applications in the food and pharmaceutical sectors.
The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO ( UID/AGR/00690/2019 ) and the research contracts of J. Pinela (Project AllNatt, POCI-01-0145-FEDER-030463), L. Barros, and R.C. Calhelha. Also to ALIMNOVA-UCM research group and Art. 83 project ref: UCM 252/2017, and to the Rafael Folch Foundation for the J.I. Alonso-Esteban grant (2016/01M). This work was funded by the European Regional Development Fund (ERDF) through the Regional Operational Program North 2020, within the scope of Project NORTE-01-0145-FEDER-023289: DeCodE. To FEDER-Interreg España-Portugal programme for financial support through the project 0377_Iberphenol_6_E. Authors are grateful also to the Ministry of Education, Science and Technological Development of Serbia (Grant No. OI 173,032).
