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Dear colleagues, we are extremely honoured to present to you the Proceedings of the international conference 19th Ružička Days, which was successfully held on September 21–23, 2022, in Vukovar, Croatia, in the hometown town of our famous Croatian scientist and first Nobel laureate, professor Leopold (Lavoslav) Ružička. The main goals of the Conference were to promote excellence, originality and innovation of interdisciplinary scientific research as well as the practical application of the obtained results through collaboration with industry, emphasizing thus the recognizable slogan of the Ružička Days conference: "Today Science – Tomorrow Industry". In addition, the Conference gave the opportunity for meetings, exchanging the ideas, opinions, experiences and cooperation among participants from different working surroundings. It is also important to point out that since 2008, within the international conference Ružička Days, Meeting of Young Chemists has also been held, where high school students, with the help of their mentors, present papers in the field of chemistry, with the aim to direct students and young people to the technical and natural sciences, especially chemistry. In its seventh issue (2011, 2013, 2015, 2017, 2019, 2021) the Proceedings publishes scientific and professional full papers of high quality in the following sections: Chemical analysis and synthesis (10), Chemical and biochemical engineering (3), Food technology and biotechnology (4), Chemistry in agriculture and forestry (1), Environmental protection (9) and 8th Meeting of Young Chemists (3). Full-length papers were subjected to an international review procedure done by eminent experts from the corresponding fields, to whom we express our gratitude, but they were not subjected to linguistic proofreading. On behalf of the Scientific and Organizing Committee of the 19th Ružička Days we cordially thank all the authors, reviewers, participants, lecturers, organizers, especially the international organizers EuCheMS and EHEDG, auspices and sponsors, and all the others who, in any way, supported the Conference and contributed to the preparation of the Proceedings, especially to our highly skilled and committed associates, who have put a lot of effort in the preparation of these Proceedings. At the very end, special thanks to our young, future scientists and their mentors who are faithful participants of the Meeting of Young Chemists of the Ružička Days conference. Enjoy the extremely interesting scientific and professional papers contained in these Proceedings, until the next 20th jubilee of Ružička Days in 2024! We are looking forward to meeting you again in Vukovar! Yours sincerely, Chief Editors Jurislav Babić Vesna Ocelić Bulatović Dajana Kučić Grgić

Essential oils from Mediterranean wild plants are widely used, but the hydrodistillation residues produced in parallel with these essential oils are significantly understudied and underexploited. Since there are only fragmentary data in the literature, we have, for the first time, systematically analyzed the chemical composition of the by-products obtained after hydrodistillation of sage, bay laurel, and rosemary leaves, i.e., hydrolates, water residues, and solid residues. The chemical composition of the hydrolates changed compared to their respective essential oils towards the dominance of more hydrophilic, oxygenated compounds, such as camphor in sage, 1, 8-cineole in bay laurel, and berbenone in rosemary. However, some compounds, mostly sesquiterpenes, which were present in considerable amounts in essential oils, were absent or only present in very small amounts in the hydrolates. Furthermore, both the water and the solid residues were rich in polyphenols, such as procyanidins in bay laurel and rosmarinic acid in rosemary and sage. In conclusion, we demonstrate the valuable chemical composition of sage, rosemary, and bay laurel hydrodistillation by-products and discuss a wide range of their possible applications.

Kemijska karakterizacija hlapljivih spojeva pčelinje peludi od velike je važnosti za procjenu njezine kvalitete. Hlapljivi spojevi izolirani su metodom mikroekstrakcije vršnih para na krutoj fazi (SPME) koristeći dva različita vlakna različite polarnosti. Dobiveni podaci analizirani su spregnutom tehnikom plinska kromatografija- spektrometrija masa (GC-MS). SPME metodom identificiran je 21 različiti spoj. Identificirani spojevi mogu se svrstati u sljedeće kemijske skupine: kiseline, alkoholi, esteri, ketone i aldehidi.

Travarica je jako alkoholno piće koje u Hrvatskoj ima dugu tradiciju proizvodnje, posebice na području Dalmacije, Istre i otoka. Pripada skupini specijalnih rakija te se proizvodi aromatiziranjem vinskog destilata, komovice, lozovače ili voćnih rakija odabranim aromatičnim biljem ili njihovim maceratima [1]. U ovom radu analiziran je aromatični profil rakija travarica kupljenih na domaćem tržištu. Hlapljivi spojevi izolirani su pomoću mikroekstrakcije vršnih para na krutoj fazi (HS- SPME) korištenjem CAR/PDMS i DVB/CAR/PDMS vlakana, te analizirani vezanim sustavom plinska kromatografija-masena spektrometrija (GC-MS). Identificirani hlapljivi spojevi pripadaju sljedećim kemijskim skupinama: esteri, alkoholi, ketoni, ugljikovodici, acetali i cikloeteri (oksidi). Među hlapljivim spojevima dominantni su bili esteri, a najzastupljeniji spoj u svim uzorcima bio je etil- dekanoat koji je karakteriziran voćnim aromama [2]. Dobiveni rezultati ukazali su na postojanje razlika u aromatičnom profilu rakija travarica, što je bilo i očekivano obzirom da svaki proizvođač ima svoju recepturu i specifičnost u tehnološkom procesu proizvodnje.

To enhance the essential oils yields for hydrodistillation of bay laurel and sage, the impact of ultrasonic and enzymatic pretreatment (under optimized xylanase activity) was investigated. Response surface methodology (RSM) was used to optimize the reaction conditions of pH, temperature, and reaction time to obtain maximum xylanase activity. The impact of optimized conditions during enzymatic pretreatment induced variations in the essential oil yields. After the pretreatments, bay laurel and sage essential oils were isolated using Clavenger type apparatus and their yields were measured and compared with the essential oils obtained from non-treated plant materials (no pretreatment control). In order to determine the impact of pretreatments on the chemical composition, isolated essential oils were analyzed by gas chromatography and mass spectrometry (GC-MS), and afterward, the correlations were tested using Spearman’s test. The main constitutes of the sage essential oils are oxygenated monoterpens (α- and β-thujone, 1, 8-cineole and camphor). 1, 8-cineole is the major component of bay laurel essential oils, followed by α-terpinyl acetate, and several monoterpene hydrocarbons and phenylpropane derivates with dominant components eugenol and methyleugenol. Several chemical compounds (mostly oxygenated monoterpenes) of bay laurel and sage essential oils were detected in greater quantity after the ultrasonic and enzymatic pretreatments in comparison to untreated plant material.However, the results showed that despite optimization, the activity of xylanase did not significantly affect the quantity and quality of bay laurel and sage essential oils. The main advantage of ultrasonic extraction is shortening of the pretreatment time and only 10 minutes of ultrasonic pretreatment before the enzymatic pretreatment caused 50 % enhancement of sage and 40 % of bay laurel essential oil yields. Due to their chemical composition (oxygenated monoterpenes, monoterpene and sesquiterpene hydrocarbons), the essential oils obtained by the ultrasonic and enzymatic pretreatment prior hydrodistillation possess potential in the food industry applications.

U ovom radu analiziran je kemijski sastav hlapljivih spojeva komercijalnih piva, pivskih stilova: pale lager, dunkel, pale ale i hefeweizen. Hlapljivi spojevi izolirani su metodom mikroekstrakcije vršnih para na krutoj fazi (SPME) korištenjem dva različita vlakna te su analizirani vezanim sustavom plinska kromatografija–spektrometrija masa (GC-MS). Identificirani spojevi mogu se svrstati u sljedeće kemijske skupine: alkoholi, esteri, terpeni i karbonilni spojevi.

The essential oil manufacture produces a significant quantity of co-products. These potentially valuable hydrodistillation residues include hydrolates contain a remarkable source of bioactive molecules. In this study, we have focused on aromatic Mediterranean plants rich in volatile compounds: bay laurel, rosemary and sage. Their essential oils are frequently used, but hydrodistillation residues produced in parallel with these essential oils are much less explored. Despite rich bioactive content, these fractions are often underexploited or even considered waste. Increasing market demand for essential oils resulted in the development of many innovative methods for improvement of their yield and composition. Traditional extraction technologies prior hydrodistillation mainly related to the high temperature mainted for long extraction periods and the consumption of hazardous organic solvents as well as low extraction efficiency of desired compounds. So, we have analysed different pretreatments prior to hydrodistillation i.e. reflux extraction, ultrasound and enzyme assisted extraction on chemical composition of hydrolates in bay laurel, rosemary and sage. GC-MS analysis showed that the hydrolates of all plants were richest in oxygenated monoterpenes: up to 46%, 42% and 30% of total peak area in bay laurel, rosemary and sage hydrolates, respectively. Sesquiterpenes were also well represented: up to 42%, and 10% of total peak area in rosemary and bay laurel hydrolates, respectively. Dominant compounds were confirmed: 1, 8-cineole, camphor, borneol and berbenone in rosemary hydrolates, 1, 8-cineole, linalool, camphor, α- and β-terpineol, methyleugenol and eugenol in bay laurel hydrolates and 1, 8-cineole, camphor, borneol and berbenone in sage hydrolates. In general, the pretreatments didn’t significantly affect the volatile compounds of hydrolates (p

Saprolegnia parasitica, uzročnik saprolegnioze salmonidnih riba i Aphanomyces astaci, uzročnik račje kuge, oomicetni su patogeni koji uzrokuju značajne ekonomske štete u akvakulturi. Budući da su kemikalije koje se koriste za njihovu kontrolu štetne za ljude i okoliš, cilj ovog istraživanja je istražiti ekološki prihvatljive metode njihove inhibicije. Testiran je inhibicijski potencijal eteričnih ulja odabranog samoniklog mediteranskog bilja, kadulje (Salvia officinalis L.), ružmarina (Rosmarinus officinalis L.) i lovora (Laurus nobilis L.) prema rastu micelija i klijavosti zoospora patogena te su određene EC50 vrijednosti. Testirana eterična ulja bila su bogata hlapivim bioaktivnim komponentama, pretežno monoterpenima, te su pokazala inhibicijsku aktivnost prema rastu micelija i klijavosti zoospora, naročito eterično ulje kadulje koje je imalo najsnažnije djelovanje. To se dijelom može pripisati dominantnim komponentama, primjerice kamforu, ali još vjerojatnije sinergističkom djelovanju velikog broja komponenti. Micelij i zoospore patogena A. astaci bile su osjetljivije od istih razvojnih stadija patogena S. parasitica, gdje je samo eterično ulje kadulje u potpunosti inhibiralo rast micelija. Zaključno, dobiveni rezultati mogu poslužiti kao osnova budućih in vivo istraživanja i razvoja ekološki prihvatljivih metoda kontrole patogenih oomiceta u akvakulturi.

Introduction Saprolegnia parasitica and Aphanomyces astaci (Oomycetes) are pathogens with negative impact in freshwater aquaculture. Saprolegnia parasitica causes saprolegniosis, a disease affecting mostly salmonid fishes, while A. astaci causes crayfish plague. Chemicals harmful to humans and the environment are being used globally in aquaculture facilities to prevent the spread of these pathogens. Thus, the development of new, ecologically acceptable methods for their control is urgently needed. The aim of this study was to examine whether propolis, known for its antimicrobial properties and stimulatory effect on the host immune system, can inhibit the life stages of A. astaci and S. parasitica in vitro. Materials and methods Two propolis formulations were used: P1 (pure propolis in ethanol), and P2 (propolis in ethanol with the addition of sage and pepper mint). Their chemical composition was determined by ultra- performance liquid chromatography-tandem mass spectrometry (UPLC- MS/MS) and gas chromatography/mass spectrometry (GC-MS). Two main life stages of the oomycete pathogens, namely mycelium and zoospores, were treated with propolis formulations and their main components, pinocembrin and chrysin. The effect of these compounds on mycelial growth was assessed using the disk diffusion assay and radial growth inhibition test, followed by determination of EC50 values. To test the inhibition of zoospore germination, sporulation was induced by washing the mycelium grown in liquid PG1 with natural water. Test compounds were added to the resulting zoospore suspension in a range of concentrations, and their effect was assessed by comparing the percentage of germinated zoospores with the results of control experiments. Malachite green, with known toxicity towards A. astaci and S. parasitica, was used as a positive control. Results Both propolis samples were rich in volatile and polyphenol compounds. As shown by UPLC-MS/MS analysis, chrysin was most abundant in both propolis samples (up to app. 50 µg/mL), followed by pinocembrin in P2 (4 µg/mL). Significantly higher number of different volatile components was found by GC-MS in P2 than in P1 propolis sample, probably because of addition of sage and pepper mint. In case of S. parasitica, both propolis formulations moderately inhibited the mycelial growth: EC50 (P1) = 206.2 µg/mL, EC50 (P2) = 206.6 µg/mL for P2, when compared with a known inhibitory compound malachite green (EC50 = 0.1 µg/mL). In contrast, EC50 values for P1, P2, and malachite green for mycelial growth inhibition of A. astaci were up to 36 times lower (5.6, 8.6, and 0.02 µg/mL, respectively). Considering zoospore germination, the minimal concentration that caused complete inhibition of S. parasitica germination (minimum inhibitory concentration, MIC) was 62.0 and 39.0 µg/mL for P1 and P2 propolis samples, respectively, while for malachite green it was 0.08 µg/mL. Similar results were obtained for Aphanomyces astaci zoospores: MIC was 31.3 and 39.0 µg/mL for P1 and P2, respectively, while malachite green inhibited zoospore germination at a concentration of 0.04 µg/mL. The inhibitory potential of main propolis components, chrysin and pinocembrin, was also tested but these compounds didn´t show significant anti-oomycete activity when applied in concentrations determined in propolis samples. This suggests that the observed anti-oomycete activity of propolis formulations was probably due to synergistic activity of a number of minor bioactive components. Conclusions Our results demonstrate the inhibitory activity of propolis towards life stages of pathogenic oomycetes S. parasitica and A. astaci. Interestingly, S. parasitica mycelium was relatively resistant to propolis in comparison to mycelium of A. astaci, but zoospores of both species (as main infection agents) were highly susceptible. Future in vivo testing is needed to explore the suggested host- protective effects of propolis during the infection process and to demonstrate its applicability as a feed additive in the fish farms.

Mnoštvo bioloških spojeva u medu nisu stabilni, naročito hlapljive tvari, a njihove se strukture mogu transformirati tijekom zrenja meda, skladištenja te u procesu dobivanja proizvoda od meda uslijed djelovanja visoke temperature. Cilj ovog rada je bio identificirati hlapljive i poluhlapljive spojeve unutar proizvoda od meda. Spojevi su izolirani ultrazvučnom ekstrakcijom (USE) koristeći otapala pentan : dietil-eter (1:2, v/v) i diklormetan. Druga korištena metoda je mikroekstrakcija vršnih para na krutoj fazi (SPME). Izolirani spojevi su analizirani vezanim sustavom plinska kromatografija-spektrometrija masa (GC-MS). Najzastupljeniji spojevi unutar uzorka su bili: 5-hidroksimetilfurfural (21, 9- 43, 9 %), 2-furankarboksialdehid (furfural ; 16, 3 %), mnogi terpeni i derivati benzena. Specifičan spoj izoliran ultrazvučnom ekstrakcijom koristeći diklormetan kao otapalo je tzv. malina keton (4- (4-hidroksifenil)-butan-2-on (0, 9 %).

The present study represents the continuation of our research on chemistry of volatile compounds from wild-growing Brassicaceae plants 1-5. The organic compounds typically presented in plants of Brassicaceae family are glucosinolates. While glucosinolate are nonvolatile compounds, their decomposition products are volatile mostly sulfur-containing compounds. This study is focused on extraction of volatile compounds of two plants, Capsella rubella and Cardaria draba, using headspace solid phase microextraction (HS-SPME), and their analysis by gas chromatography-mass spectrometry (GC-MS). HS-SPME is a simple, fast, relatively inexpensive and solvent-free technique which is a widely used for the extraction of volatile compounds from fruits, vegetables and flowers while the GC-MS is the main analytical method for the analysis of volatile profiles of various origin. Capsella rubella and Cardaria draba are wild-growing Brassicaceae plants widespread in mediterranean part of Croatia. They grow on open places exposed to sunlight such as fields, pastures, meadows, waste places, and along roadsides. The volatile sulfur-containing compounds have not been so commonly examined in these two plants 1, 2, especially not using above mentioned HS-SPME coupled with GC-MS. Results presented in this study revealed that sulfur-containing compounds were qualitatively and quantiatively dominating constituents in headspaces of investigated plants. Thus, C. rubella headspaces were characterized by a high percentage of allyl isothiocyanate (79.3 and 67.2%) followed by allyl thiocyanate (11.0 and 8.8%). Dominating compound in headspaces of Cardaria draba was 4-(methylthio)butyl-isothiocyanate (91.4 and 94.2%). Considering the most abundant compounds in headspaces of investigated plants, it can be concluded that the main glucosinolate of Capsella rubella is sinigrin and of Cardaria draba is glucoerucin.

Uvod: Posljednjih se godina intenzivno istražuju nove metode izolacije eteričnih ulja, s ciljem povećanja njihovog prinosa. Ciljevi: Cilj ovog istraživanja bio je istražiti da li različiti predtretmani vodene destilacije mogu povećati prinos eteričnog ulja kadulje, ružmarina i lovora te utvrditi eventualne promjene u kemijskom sastavu eteričnih ulja. Metode: Vodenoj destilaciji predhodili su različiti predtretmani: klasična ekstrakcija refluksiranjem, ekstrakcija refluksiranjem uz dodatak enzima pektinaze, celulaze i ksilanaze te ultrazvučna ekstrakcija. Kemijski sastav dobivenih ulja analiziran je GC- MS i NMR analizom. Rezultati: Svi predtretmani povećali su prinos eteričnih ulja u usporedbi s negativnom kontrolom, pri čemu je kvaliteta ulja ostala nepromijenjena. No, predtretman ekstrakcijom refluksiranjem s dodatkom enzima nije povećao prinos ulja u odnosu na sami predtretman ekstrakcijom refluksiranjem (kontrola bez enzima). Ovo upućuje na to da je povećanje prinosa ulja uzrokovala ekstrakcija refluksiranjem, a ne enzimska aktivnost, i suprotno je navodima mnogih ranijih istraživanja. Međutim, u tim istraživanjima prinos ulja nakon predtretmana enzimima uspoređen s negativnom kontrolom (bez predtretmana), umjesto s kontrolom bez enzima. Zaključno, rezultati ovog istraživanja pokazali su da predtretmani ultrazvukom i ekstrakcijom refluksiranjem mogu biti korisni u proizvodnji eteričnih ulja navedenih biljaka, ali da primjena enzima u ovu svrhu treba biti dodatno istražena.

Kemijski sastav hlapljivih spojeva lista koprive ovisi o nekoliko faktora, kao što su: sorta, sezona, stanje lišća, geografski i klimatski uvjeti. U ovom radu analiziran je kemijski profil hlapljivih spojeva tri komercijalna uzorka suhog lista koprive. Analiza je provedena mikroekstrakcijom vršnih para na krutoj fazi (HS-SPME) koristeći vlakno s prevlakom DVB/CAR/PDMS (divinilbenzen/karboksen/polidimetilsiloksan, 50-30 μm). Ukupno je identificirano 38 spojeva, od čega u prvom uzorku 26, u drugom 20 i u trećem 22 spoja. Glavni spojevi vršnih para izolirani HS-SPME metodom s DVB/CAR/PDMS prevlakom bili su: trans-anetol (25, 66-52, 55 %), trans-β-kariofilen (2, 41-13, 37 %), limonen (0, 81-12, 92 %), karvon (1, 28-10, 74 %), α-kopaen (1, 05-6, 37 %) i estragol (1, 54-3, 57 %). Općenito, isparljivi spojevi lista koprive prethodno su pokazali antioksidacijsko, antibakterijsko i antigljivično djelovanje koje može biti korisno za prehrambenu, farmaceutsku i kozmetičku industriju.

Proceedings contains 13 original scientific papers, 10 professional papers and 2 review papers which were presented at "10th International Scientific and Professional Conference WITH FOOD TO HEALTH", organised in following sections: Nutrition, Dietetics and diet therapy, Functional food and food supplemnents, Food safety, Food analysis, Production of safe food and food with added nutritional value.

In the present study volatile compounds and shelf-life of low-sodium breads with the added aromatic plants (ground spices) were studied. The main ingredients of tested breads were wheat flour, water, ground spices (wild thyme, chives and basil), yeast and salt (max. 0.12 g of sodium per 100 g of bread). Volatiles were determined using headspace solid phase microextraction (HS-SPME) with a PDMS/DVB fibre coat followed by gas chromatography mass-spectrometry (GC-MS). A total of 22, 13 and 12 compounds were identified in bread with wild thyme (A), chives (B) and basil (C), respectively. The major compounds in bread A were thymol (50.32%), p-cymene (13.86%), trans-anethole (6.07%), methyl thymyl ether (5.43%), cravacrol methyl ether (5.23%), carvacrol (3.34%) and trans-caryophyllene (3.19%) ; in bread B trans-anethole (45.11%), carvone (12.44%), (E)-hept-2-enal (6.28%), camphor (4.06%), oct-1-en-3-ol (3.34%) and 2-phenylethanol (3.08%) ; in bread C p-allylanisole (24.59%), linalool (21.12%), β-burbonene (19.03%), trans-anethole (13.41%), trans-α-bergamotene (5.43%), undecanal (4.23%) and carvone (3.02%). The identified volatiles were specific for each aromatic plant and thus expected. Breads were stored under ambient temperature (25 ± 1 °C) and their moisture content, water activity and overall acceptability were estimated at 2 days interval for 20 days. The examined aromatic plants extended the shelf-life and showed antifungal activity, and the best effect showed bread with the added wild thyme, then chives and finally basil.

This work deals with the influence of convective drying on different temperatures on aroma profile of Swiss chard leaves as a part of a pasta enrichment plan. The Swiss chard (Beta vulgaris L. ssp. cicla) belongs to the Chenopodiaceae family [1] and is commonly used in diet as leafy green vegetable, raw or cooked (in salads, soups, pastas, etc.), then as food supplement in dehydrated pulverized form or in food industry as natural food colorant or pasta stuffing. Swiss chard leaves were collected in the anthropogenized areas (gardens, orchards and pastures) of Šibenik-Knin County. Plant material was dried at three temperature levels (20 °C – ventilation only, 40 °C and 60 °C) in convective dryer. Volatile compounds were isolated by headspace solid-phase microextraction (HS-SPME) using fibre coated with polydimethylsiloxane/ divinylbenzene/ carboxene (DVB/CAR/PDMS) and analyzed by gas chromatography-mass spectrometry (GC-MS). The dominant volatile compound identified was trans-2-hexenal present both in fresh plant material and in dried samples. Other identified volatile compounds belong to aldehydes, alcohols and ketones. Drying temperatures influence concentrations and formation or degradation of volatile compounds.

Rosa canina L. (Rosaceae), a dog rose, is one of the most widespread wild species of the genus Rosa which grow almost everywhere in Croatia, especially in its Mediterranean region. The plant is appreciated for its shiny red fruits, called rosehips, whose consumption is popular in Croatia mainly in form of marmalade, jam and flavour teas. It is well known that rose hips of R. canina are rich source of various bioactive compounds such as vitamins (especially vitamin C), phenolic compounds (especially flavonoids), carotenoids and fatty acids, with potential positive effect on human health. Most studies of R. canina rosehips have been focused primarily on those compounds and their antioxidant and anti-inflammatory properties. However, literature data regarding volatile compounds of R. canina hips are rather limited. Hence, the aim of this study was to characterize the volatile compounds of R. canina hips originating from Croatia. The volatile compounds, commonly designated as aroma compounds, are naturally present in fruits. Those compounds, together with non-volatile compounds responsible for taste, are responsible for the flavour of fruits. A great variety of aroma compounds is present in fruits. Regarding various rose hip species, volatile compounds comprise mostly alcohols, aldehydes, ketones, monoterpenes and sesquiterpenes. According to literature, the sampling of the rosehips’ volatile compounds was achieved by various techniques, such as hydrodistillation, extraction in Soxhlet apparatus, headspace solid phase microextraction and immersion solid phase microextraction, always followed by gas chromatography-mass spectrometry (GC-MS) analysis.Hydrodistillation, the most usual method for the essential oils isolation, i.e. volatile compounds, was chosen for the isolation of volatile compounds from R. canina fruits. As far as we know, only one study reported the volatile compounds of R. canina obtained by hydrodistillation of the entire rosehips. In this study, the entire rosehips were used for the isolation of volatiles, as well as seeds and fleshy pulp separately. The chemical composition of the essential oils was analyzed by GC-MS. The dominating compound in R. canina essential oil, obtained from entire rosehips, was norisoprenoid vitispirane followed by ketone 6-methylhept-5-en-2-one. Vitispirane was identified in R. canina fruit pulp, too, but in much smaller amount, while the content of 6-methylhept-5-en-2-one was almost the same. Other quantitatively important components in this sample were C9– C22 hydrocarbons, and aldehydes hex-2-enal, furfural and hept-2-enal. The essential oil isolated from R. canina seeds was characterized by a high content of phenylacetaldehyde, moderate content of benzyl isothiocyanate and absence of vitispirane and 6-methylhept-5-en-2-one. Regarding terpenes, the typical constituents of essential oils, monoterpene limonene was dominated component in all essential oils.

Essential oil compositions of fresh leaves, flower stems and rhizomes obtained by hydrodistillation from different Croatian populations of Petasites albus (L.) GAERTN. and P. hybridus (L.) G.GAERTN., B.MEY. & SCHERB. (four of each species) were investigated using gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. Altogether, 118 constituents were identified, accounting for 81.19 – 96.81% of total oil composition. All essential oils were characterized by oxygenated sesquiterpenes, with distinct compounds recorded for both investigated species. Clear separation between the two species was confirmed by principal component analysis and hierarchical cluster analysis. This is the first study that recorded intraspecific variations of essential oil constituents from P. albus and P. hybridus. Obtained results could contribute to the understanding of their medicinal and nutritional value.

Tree of heaven (Ailanthus altissima (Mill.) Swingle) is a fast-growing, very aggressive and invasive deciduous tree and the unifloral honey from this plant is rare. Due to its biodegradability, eco- friendliness and low cost, a natural honey fulfils the requirements for a non-toxic green corrosion inhibitor. Several studies confirmed the honey potential application as the corrosion inhibitor of different metals and alloys, but there are no reports on the anticorrosion capacity of this honey type. In the present study the ability of the honey to protect reactive surfaces of Fe and Sn, the main constituent of tinplate, against corrosion in a saline solution, pH 3.0, was tested using dc electrochemical methods and electrochemical impedance spectroscopy (EIS). The nondestructive EIS method was used at the open- circuit potential (EOCP) under static conditions. EIS parameters obtained in situ in a wide frequency range were correlated to the phenomena that occur simultaneously at different time scales: the charge- transfer resistance, capacitance and resistance of the surface film, and the resistance to the transport of metal species through the film. From dc and ac measurements the corrosion kinetic parameters were derived. Results show that Ailanthus altissima (Mill.) Swingle honey in investigated concentration range inhibits corrosion of Sn while the inhibitory activity on Fe was not established.