Safety assessment of hops (Humulus lupulus) extract as a cosmetic ingredient using the threshold of toxicological concern approach

Uporaba izvlečka hmelja sega že v daljno zgodovino, ko je bila rastlina znana predvsem po svojih pomirjujočih učinkih. Uporaba izvlečka hmelja je danes razširjena vse od pivovarske, farmacevtske do kozmetične industrije. Široko področje uporabe hmelja nam omogočajo vsebujoče spojine, ki izkazujejo številne pozitivne učinke delovanja. Kljub tem pozitivnim lastnostim pa obstajajo tudi meje, do katerih je uporaba rastlinskih izvlečkov varna. Pri uporabi rastlinskih izvlečkov v kozmetičnih izdelkih moramo za določitev teh mej preučiti posamezne spojine, ki jih rastlina vsebuje. V sklopu naše diplomske naloge smo preučevali spojine, ki se nahajajo v rastlini in izvlečku hmelja. S pomočjo literature smo poiskali najpogostejše spojine, ki se pojavljajo v rastlini. S pomočjo računalniškega programa ChemDraw smo tem spojinam izračunali fizikalno-kemijske lastnosti, na katerih so temeljili naši izračuni. V kombinaciji s podatki o koncentracijah, v katerih se nahajajo v rastlini, smo jim določili oceno varnosti z uporabo pristopa s pragom toksikološkega tveganja (TTC). TTC temelji na razvrščanju spojin v tri različne Cramer-jeve razrede, kar odraža njihovo nizko, srednjo ali visoko toksičnost. Za razvrščanje spojin v Cramer-jeve razrede smo uporabili računalniški program Toxtree. Na podlagi metode, ki so jo opisali Kroes et al. (2007), smo z izračunano maksimalno hitrostjo difuzije spojin skozi kožo, določili še potencialen obseg absorpcije spojin v 24 h. Večini spojin, ki se nahajajo v hmelju, smo določili majhen ali srednji obseg absorpcije, v nekaterih primerih pa tudi velik obseg. Določili smo tudi potencialno sistemsko izpostavljenost, ki je presegala vrednosti Cramer-jevih razredov toksičnosti, pri alfa in beta kislinah, δ-kadinenu, terpineolu, limonen oksidu, linaloolu, mircenolu in naringeninu. Na podlagi nekaterih študij, v katerih ni bilo zaznati toksičnih učinkov teh spojin, ki so bile uporabljene v veliko višjih odmerkih od tistih postavljenih za Cramer-jeve razrede, smo predvidevali, da je izvleček vseeno varen, saj so vrednosti TTC postavljene precej nizko. Nizko mejo Cramer-jevih razredov smo lahko potrdili tudi na podlagi poiskanih vrednosti NOAEL, ki se določajo v eksperimentih na živalih. Iz vrednosti NOAEL smo izračunali varni dnevni odmerek, ki je bil v vseh primerih veliko večji kot primerljiva vrednost TTC. Na podlagi vseh izračunov in literaturnih podatkov smo lahko na koncu potrdili, da je izvleček hmelja varen za uporabo.The use of hop extract dates back to ancient history when hop was known mainly for its calming effects. Nowadays, hop extract is used in the brewing industry, pharmacy, and cosmetics industry. Containing ingredients enable a wide area of hops usage, which has numerous positive effects. In addition to all positive characteristics, there are limits to the safe usage of vegetable extracts. When using vegetable extracts in cosmetic products, it is important to study particular compounds of vegetables and thus establish those safe limits. As part of the Diploma Thesis, the compounds that can be found in the hops plant and extract, were studied. Using the literature, the most common plant constituents were found. Using the ChemDraw software, the physicochemical characteristics of compounds were calculatedand those were the basis of our calculation. Combined with data on concentrations in which they can be found in plants, the safety assessment was conducted using the threshold of toxicological concern approach (TTC). TTC approach is based on the classification of compounds into three different Crammer’s classes, with low, medium, or high toxicity. The computer program Toxtree was used for classification of compounds into Cramer’s classes. Using the method, described by Kroes et al. (2007), we used the assessed maximal rate of compound diffusion through the skin and assessed the potential extent of compound absorption in 24 hours. Most compounds in hops have low or medium extent of potential absorption, but in some cases also potential for high extent of absorption. We then determined potential system exposure to all compounds and discovered that alpha and beta acids, δ-cadinene, terpineol, limonene oxid, linalool, myrcenol, and naringenin exceeded the exposure limits of their corresponding Cramer’s classes. Based on some studies in which the toxic effects of those compounds were not found, although they were used in much higher concentrations as represented by Cramer’s classification, it has been presumed that the extract is safe since the TTC values are substantially low. Moreover, the low limits of Cramer’s classes are confirmed based on NOAEL values, which are determined in animal experiments. From the NOAEL values, the safe daily dose was determinedthose daily doses were much higher than comparable TTC values. Based on all the calculations and literary data, it was confirmed that the hops extract is safe for use