Testiranje stabilnosti hidrolatov poprove mete (Mentha × piperita) in pelargonije (Pelargonium graveolens)

Ravnikar, Eva (author), Kočevar Glavač, Nina (mentor), Schoss, Katja (comentor)

Eterična olja so koncentrirane mešanice lipofilnih hlapnih spojin, ki jih pridobivamo z destilacijo, hidrolati pa so vodne raztopine hlapnih vodotopnih komponent, ki poleg eteričnega olja nastanejo pri tem procesu. V primerjavi z eteričnimi olji, ki imajo dobro raziskane farmakološke učinke ter široko uporabo v kozmetiki, farmaciji, živilstvu in aromaterapiji, so hidrolati še vedno precej manj raziskani. Da bi to področje bolj raziskali, smo s pomočjo plinske kromatografije, sklopljene z masno spektrometrijo (GC-MS), proučevali stabilnost hidrolatov poprove mete (Mentha × piperita) in pelargonije (Pelargonium graveolens). Pripravili smo eterično olje in hidrolat obeh zdravilnih rastlin, kondenzirano vodno fazo Clevengerjeve destilacije in dva izvlečka hidrolata (z etilacetatom in s heksanom) ter analizirali njihovo kemijsko sestavo. Nato smo 5 mesecev testirali stabilnost hidrolatov hranjenih pri različnih pogojih: temperatura (2–8 °C, sobna: 20 – 25°C in 40 °C), material vsebnika (temno steklo, polietilen, polietilen visoke gostote ter aluminij) in izpostavljenost svetlobi (prozorni stekleni vsebniki). Mesečno smo izvajali analize njihove sestave in vrednosti pH ter ugotavljali skupno koncentracijo hlapnih spojin v hidrolatih. Analiza sestave vzorcev poprove mete in pelargonije je pokazala, da v obeh rastlinah prevladujejo oksigenirani monoterpeni. V eteričnem olju poprove mete smo zaznali 34 spojin in v hidrolatu 10, v vseh vzorcih pa je prevladoval menton. V eteričnem olju pelargonije smo identificirali 66 spojin, le 4 spojine pa smo zaznali v hidrolatu. Najbolj zastopan je bil citronelol. Skupna koncentracija hlapnih spojin je znašala 0,94 mg/mL v hidrolatu poprove mete in 0,08 mg/mL v hidrolatu pelargonije. Stabilnost hlapnih spojin v vzorcih poprove mete je bila odvisna predvsem od materiala in tudi temperature. Največje znižanje koncentracij (za > 95 %) in vrednosti pH (s 6,33 na 4,02) smo zabeležili v vzorcih v polietilenskih vsebnikih. Material ovojnine je imel na vzorce pelargonije manjši vpliv, težje pa smo primerjali vpliv temperature zaradi težav z izhlapevanjem vzorcev. Vseeno se je kot optimalna izbira za shranjevanje hidrolata pelargonije izkazalo shranjevanje pri nizkih temperaturah, saj je vzorec, ki smo ga hranili v hladilniku ves čas testiranja vseboval najvišje koncentracije hlapnih spojin. Optimalna stabilnost hidrolatov je dosežena, kadar preprečimo kemijske reakcije hlapnih spojin in mikrobiološko kontaminacijo. V primeru poprove mete in pelargonije smo to dosegli s shranjevanjem v steklenem vsebniku v temnem in hladnem prostoru.

• Language: Slovenian
• Keywords: destilacija, ekstrakcija, eterično olje, hidrolat, metoda GC-MS, pelargonija (Pelargonium graveolens), poprova meta (Mentha × piperita)
• Work type: Master's thesis/paper
• Organization: FFA - Faculty of Pharmacy
• Year: 2025
• PID: 20.500.12556/RUL-169342
• Publication date in RUL: 24.05.2025

Secondary language

• Language: English
• Title: Stability testing of hydrolates of peppermint (Mentha × piperita) and rose geranium (Pelargonium graveolens)

Abstract

Essential oils are concentrated mixtures of lipophilic volatile compounds obtained by distillation, while hydrolates are aqueous solutions of volatile water-soluble components produced alongside essential oils during this process. Compared to essential oils, which have well-researched pharmacological effects and are widely used in cosmetics, pharmaceuticals, food, and aromatherapy, hydrolates remain relatively under-researched. To further explore this field, we studied the stability of peppermint (Mentha × piperita) and rose geranium (Pelargonium graveolens) hydrolates using gas chromatography coupled with mass spectrometry (GC-MS). We prepared the essential oil and hydrolate of both medicinal plants, as well as the condensed aqueous phase from Clevenger distillation and two hydrolate extracts, one with ethyl acetate and one with hexane, and analyzed their chemical composition. We then tested the stability of the hydrolates over five months under different conditions: temperature (2–8 °C, room temperature, 40 °C), container material (glass, polyethylene, high-density polyethylene, aluminum), and light exposure (glass containers). Monthly, we analyzed their composition and pH and determined the total concentration of volatile compounds. The predominance of oxygenated monoterpenes was observed in both plants. In peppermint essential oil, 34 compounds were detected and 10 in the hydrolate, with menthone being predominant in all samples. Geranium essential oil contained 66 compounds, and only 4 were found in the hydrolate, with citronellol being most abundant. The total concentration of volatile compounds was 0,94 mg/mL in the peppermint hydrolate and 0,08 mg/mL in the geranium hydrolate. The stability of volatile compounds in peppermint samples depended mainly on the material and also on temperature. The hghiest decrease in concentrations (> 95 %) and pH (from 6,33 to 4,02) occurred in polyethylene containers. The packaging material had a smaller impact on the pelargonium samples, but it was more difficult to compare the effect of temperature due to issues with sample evaporation. Nevertheless, storage at low temperatures proved to be the optimal choice for preserving pelargonium hydrolate, as the sample kept in the refrigerator throughout the testing period contained the highest concentrations of volatile compounds. Optimal hydrolate stability is achieved by preventing chemical reactions of volatile compounds and microbial contamination; in the case of peppermint and pelargonium, this was ensured by storage in a glass container in a dark, cool place.

• Keywords: distillation, extraction, essential oil, hydrolate, GC-MS method, geranium (Pelargonium graveolens), peppermint (Mentha × piperita)