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Advisor(s)
Abstract(s)
Nowadays there is an increasing interest in the search for bioactive compounds obtained from aromatic and
medicinal plants. Hop (Humulus lupulus L.) is known worldwide as an essential raw material for the beer
industry, however, recent studies have revealed health benefits. In the beer production process, only
the cones of hop are used, while the vegetative part of the plant is discarded and not valorized albeit its
richness in interesting compounds. In this work, we have studied the phytochemical profile of polar extracts
of hop and of the essential oil of T. zygis subsp. zygis, and further evaluated their antibacterial and antifungal
capacities. Moreover, gel formulations incorporating distinct levels of hop extracts (1.25%, 2.5% and 5%)
from cones and vegetative parts of the varieties Nugget and Polaris of hop and spontaneous hop, combined
with essential oil of Thymus zygis subsp. zygis, were developed and the stability of the new cosmetic
products was evaluated.
UHPLC-DAD-ESI-MS2 analysis was used for phytochemical study of hydroalcoholic hop extracts. The
antimicrobial properties of these extracts and of the essential oil of T. zygis subsp. zygis were determined
by microdilution broth method and the diffusion in agar test. Additionally, the stability of the gel
formulations was evaluated through a series of physical-chemical tests such as the pH, density, texture
evaluation, mechanical vibration, centrifugation, relative humidity, light test, consecutive extreme
temperature variation and evaluation of organoleptic characteristics.
The stability tests did not reveal phase separation or liquefaction of the prepared gel samples. There were
no changes recorded in vibration test, in the organoleptic characteristics of the formulations, the relative
humidity test, as well as in the extreme temperature variation test. The formulations showed an acid pH,
between 5.93±0.047 and 6.16±0.047. The apparent density of the formulations were between 1.08±0.00
Kg/m-3 and 1.12±0.00 Kg/m-3. Although hop extracts had no antimicrobial effect, the essential oil of T. zygis
subsp. zygis showed antibacterial and antifungal activities against all strains of bacteria and fungi tested,
with higher potency against S. aureus (MIC = 0.031%) than for P. aeruginosa (MIC = 1.25%). The study
of the phenolic profile of cones and vegetative parts of the polar extracts of hop, allowed the identification
of thirty compounds, of which alpha and beta acids, phenolic acids and flavonoids. In conclusion, the study
explored the vegetative part of hop that remain poorly studied allowing propose them as ingredient in
cosmetic area.
Description
Keywords
Humulus lupulus L. Hop Vegetative parts Phenolic composition Antimicrobial activity Cosmetic formulation
Pedagogical Context
Citation
Alves, Silena; Afonso, Andrea F.; Cardoso, Susana M.; Sousa, Maria João; Pereira, Olívia R. (2021). Humulus lupulus L.: cosmetic application of extracts obtained from cones and vegetative parts. In 1st Natural products application: health, cosmetic and food: livro de resumos. ISBN 978-972-745-286-6
Publisher
Instituto Politécnico de Bragança