Effect of storage on the antioxidative and antibacterial effect of hops extracts against Propionibacterium acnes
Date Issued
2016
Date
2016
Author(s)
Lu, Jia-Hui
Abstract
Hops, the female inflorescences of the hop plant (Humulus lupulus L.), are widely used in the brewing industry to add bitterness and aroma to beer. Hops have attracted a great deal of attention as a source of small molecules such as humulone, lupulone and xanthohumol with potential for beneficial effects on antibacterial,antiinflammatory, antioxidation and antiproliferation. Propionibacterium acnes (P. acnes) play important roles in common skin disease of acne vulgaris. The stability of the constituents of hops has been great important. However, hop constituents are quite unstable and sensitive to heat, light, and oxygen. In addition, oxidation and degradation occurring during the storage period reduce the active ingredients content and antibacterial activity. In order to increase application of hops, the aim of this work is to evaluate antibacterial activity of the hops extracts obtained under various extract conditions, and their antibacterial and antioxidant activity changes during storage period. Thus, in this work, hops extracts made with various ethanol concentrations (55%, 75%, 95%) and CO2 hops extract were stored at different temperatures (4°C / 25°C) for three months to study their antibacterial activity against P. acnes and antioxidant activity changes during storage period. The results showed that CO2 hops extract and 95% hops ethanol extract exhibited higher antibacterial and antioxidant activities than other hops extracts and remained stable after three months storage. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of CO2 hops extract was 2 μg/ml and 4 μg/ml, respectively. The 55% hops ethanol extract showed a significant decrease in antibacterial and antioxidant activities after storage, but the activities can be improved by storage at a lower temperature. These results suggested that the CO2 hops extract and 95% hops ethanol extract are more suitable for skin care products and the storage environment should be noticed to ensure quality of the extracts.
Subjects
Humulus lupulus
antibacterial
antioxidation
Propionibacterium acnes
Type
thesis
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