Six medicinal plants Helichrysum italicum (Roth) G. Don, Angelica archangelica L., Lavandula officinalis L., Salvia officinalis L., Melilotus officinalis L., and Ruta graveolens L. were used. The aim of the study was to compare their extracts obtained by Soxhlet (hexane) extraction, maceration with ethanol (EtOH), and supercritical CO2 extraction (SC-CO2) targeted on coumarin content (by high performance liquid chromatography with ultraviolet detection, HPLC-UV), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging capacity, and total phenols (TPs) content (by Folin–Ciocalteu assay). The highest extraction yields were obtained by EtOH, followed by hexane and SC-CO2. The highest coumarin content (316.37 mg/100 g) was found in M. officinalis EtOH extracts, but its SC-CO2 extraction yield was very low for further investigation. Coumarin was also found in SC-CO2 extracts of S. officinalis, R. graveolens, A. archangelica, and L. officinalis. EtOH extracts of all plants exhibited the highest DPPH scavenging capacity. SC-CO2 extracts exhibited antiradical capacity similar to hexane extracts, while S. officinalis SC-CO2 extracts were the most potent (95.7%). EtOH extracts contained the most TPs (up to 132.1 mg gallic acid equivalents (GAE)/g from H. italicum) in comparison to hexane or SC-CO2 extracts. TPs content was highly correlated to the DPPH scavenging capacity of the extracts. The results indicate that for comprehensive screening of different medicinal plants, various extraction techniques should be used in order to get a better insight into their components content or antiradical capacity.

Due to its high nutritive value, royal jelly usage is increasing, both in human nutrition in native form and as bioactive component in other products (dietary supplements, medicines). The database and regulations on royal jelly characteristics are established in several countries, but not in Croatia. Physicochemical characteristics: moisture, protein content, pH value, total acidity, carbohydrate composition and 10-HDA content in 13 Croatian royal jelly samples were determined with the aim of getting insight to quality of royal jelly produced in Croatia. The obtained results showed that regarding 10-HDA content, one of the most important quality parameter, all samples fulfilled the international standard for royal jelly specifications. Moisture of three samples was higher than prescribed (69.5%, 76.3% and 72.0%, respectively) while one sample had slightly lower protein content than minimum 11% prescribed in international standard. Sucrose content in two royal jelly samples was higher than 3%. Statistically significant correlations were obtained between moisture and protein content, 10-HDA and total acidity as well as between fructose and glucose content. The results of this study will contribute to creation the database of Croatian royal jelly physicochemical characteristics and thus help in setting the royal jelly quality criteria at national level

Ability of black locust (n = 7), chestnut (n = 3), lime (n = 5), mint (n = 3), and honeydew (n = 12) honeys to produce hydrogen peroxide upon dilution, as well as their glucose oxidase activity were investigated in the present study. The glucose oxidase (GOX) activity was determined by the standard horseradish peroxidase/o-dianisidin method, while hydrogen peroxide concentration in honey solutions of five different mass to volume ratios (1:1; 1:2; 1:4; 1:8; 1:16) by semi-quantitative method using MQuant™ peroxide test strips. The obtained results showed that chestnut, lime, honeydew and mint honeys exhibited high GOX activity (341.26 ± 128.78, 350.16 ± 124.91, 376.82 ± 69.02, 402.47 ± 60.99 µg H 2 O 2 /h g), while black locust honeys much lower GOX activity of 25.58 ± 21.87 µg H 2 O 2 /h g. The accumulation of hydrogen peroxide in serially diluted honeys has shown asymmetrical inverted U-shaped curve, where the increase in hydrogen peroxide accumulation with dilution reached a maximum point, after which its concentration rapidly declined. Hydrogen peroxide content in honey solutions of different mass to volume ratio varied from 0 to 294.1 µmol/L h. Lime and chestnut honeys generated the highest hydrogen peroxide content (264.71 ± 65.77, 245.10 ± 84.90 µmol/L h) on average, while black locust, mint and honeydew honeys at least two-fold lower amounts (113.40 ± 50.84, 127.45 ± 33.96, 112.75 ± 98.42 µmol/L h). Lack of correlation between glucose oxidase activity and hydrogen peroxide content indicates that the glucose oxidase activity does not present a reliable parameter for the prediction of hydrogen peroxide content produced in honey solutions.

Background. Bee pollen, a source of nutrients for adult honey bees and larvae, is produced from plant flower pollen which bees collect and mix with nectar or secretions from their salivary glands. Bee pollen contains nutritionally essential substances like proteins, lipids, amino acids, mineral substances, and vitamins but also carotenoids, flavonoids, and polyphenols. The amount of each substance contained in bee pollen depends on the botanical origin and the source region. Recently, many investigations have been concerned with the antioxidant properties of different food products. The aim of this research was to examine the antioxidant capacity of bee pollen and investigate its relationship with total phenolic and flavonoid contents. Materials and methods. Samples were collected from three locations in Croatia from April to June 2019. Sixteen bee pollen pooled samples were classified according to color and, after melissopalynological analysis, total phenolic (Folin-Ciocalteu method) and total flavonoid contents and antioxidant capacity (FRAP assay) were determined in fourteen monofloral bee pollen samples. Results. The monofloral bee pollen samples had 82-100% of their pollen originating from one botanical species. The highest total phenolic content (TPC) was measured in Prunus spp. and Salix spp. monofloral bee pollens (15.80 and 13.75 mg GAE/g, respectively), which also had the highest ferric reducing-antioxidant power (FRAP) values (124.44 and 147.61 µmol Fe 2+ /g, respectively). The samples with the lowest TPC (Crepis biennis L. and Taraxacum officinale F.H. Wigg.; 4.00 and 5.34 mg GAE/g, respectively) also had the lowest FRAP values (25.24 and 34.74 µmol Fe 2+ /g, respectively). The values for total flavonoid content (TFC) did not vary a lot between the analyzed samples (5.05-9.71 mg QE/g). Conclusion.In comparison to some other food products, bee pollen, like most bee products, appears to be a good source of antioxidants. The botanical family or botanical species of bee pollen affects the antioxidant properties of the bee pollen. Due to a lack of research on monofloral bee pollen in comparison to pooled samples, knowledge about specific parameters of different monofloral bee pollen samples should be broadened.

One of the major challenges in sustainable waste management in the agri-food industry following the “zero waste” model is the application of the circular economy strategy, including the development of innovative waste utilization techniques. The conversion of agri-food waste into carriers for the immobilization of enzymes is one such technique. Replacing chemical catalysts with immobilized enzymes (i.e., immobilized/heterogeneous biocatalysts) could help reduce the energy efficiency and environmental sustainability problems of existing chemically catalysed processes. On the other hand, the economics of the process strongly depend on the price of the immobilized enzyme. The conversion of agricultural and food wastes into low-cost enzyme carriers could lead to the development of immobilized enzymes with desirable operating characteristics and subsequently lower the price of immobilized enzymes for use in biocatalytic production. In this context, this review provides insight into the possibilities of reusing food industry wastes, namely, eggshells, coffee grounds, and brown onion skins, as carriers for lipase immobilization.