Natural plant sources, particularly the fruits of several lesser-known species, are receiving increasing amounts of attention because they contain a variety of bioactive compounds that are advantageous to human health. The production of easy-to-grow, already-used, and full of nutrients crops could be a solution to the growing problem of a lack of healthful food. One such fruit is the quince (Cydonia oblonga Mill.), which belongs to the Rosaceae family that originated in the Caucasian area and extends to other parts of the world. Quince has been studied for decades because of its unique importance in food and medicine. The characteristic pear-shaped fruit is golden yellow in appearance and has an aromatic, and acidic flavour. The low-fat fruit is rich in numerous necessary nutrients, minerals, dietary fibre, and antioxidants that have significant positive effects on health, but due to its bitterness, it is underutilized. Quince can be utilised as a raw material to create a variety of food products and is a good source of natural phenolic antioxidants, providing significant functional characteristics.

Sweet potatoes are reported to be a good source of bioactive compounds. The aim of this study was to evaluate the impact of different heat treatment methods (microwaving, steaming, and baking) and variety on the total polyphenol content and antioxidant activity of three sweet potato varieties – Beauregard (orange-fleshed), O’Henry (white-fleshed), and 414-purple (purple-fleshed). All investigated parameters were determined spectrophotometrically. The total polyphenol content was in the range of 0.53 (O’Henry) – 5.60 mg GAE.g-1 DW (414-purple) for raw flesh and 1.68 (O’Henry) – 7.03 mg GAE.g-1 DW (414-purple) for raw peel of sweet potatoes. Heat treatments caused an increase of total polyphenol content in sweet potatoes (0.98 (steamed O’Henry) – 28.04 mg GAE.g-1 DW (baked 414-purple)). In terms of antioxidant activity, the steamed samples of variety 414-purple showed the highest values of DPPH radical scavenging activity (4.51 µmol TE.g-1 DW) and Ferric reducing antioxidant power assay (19.57 µmol TE.g-1 DW) compared to the other treatment methods. Spearman´s test showed a strong positive relationship between both used methods for evaluation of antioxidant activity. All studied processing methods positively affected the total polyphenol content and antioxidant activity in sweet potatoes.

This study aims to determine the vitamin C content and antioxidant activity in different types of fruit: cornelian cherry (Cornus mas L.), service tree (Sorbus domestica), medlar (Mespilus germanica L.), pawpaw (Asimina triloba L.), persimmon (Diospyros kaki L.). The aim of the work was to compare these used methods. The fruit’s vitamin C content was determined by HPLC system Waters Separations Module 2695 with UV detector 2996. The content of vitamin C reached values from 72.238 µg. g-1 (Diospyros kaki L.) to 1114.61 µg.g-1 (Sorbus domestica). The antioxidant activity (DPPH) was determined spectrophotometrically. DPPH radical scavenging activity values were 2.28 (Mespilus germanica L.) – 12.34 μmol TE.g-1 DW (Cornus mas L.). Spearman's test showed a positive relationship between both monitored parameters. The content of vitamin C in the studied species showed a positive relationship with antioxidant activity. Due to the high content of vitamin C and antioxidant activity, future analyses should focus on the determination of other bioactive substances in these fruits.

The cultivation of sweet chestnuts in Slovakia has a century-year-old tradition. However, just a few research publications provide more comprehensive information about the chestnuts’ chemical composition of different varieties in individual growing areas. Sweet chestnuts contain various nutrients, of which carbohydrates are very important for assessing their commercial quality. Simple carbohydrates are mainly represented by glucose, fructose, sucrose, and maltose. The content of glucose was 0.178–3.152, fructose 0.271–3.170, sucrose 9.355–29.890, and maltose 0.171–1.584 g/100 g DW in chestnut samples from 27 sampling points, which are part of Slovakia’s four largest growing areas of sweet chestnuts. Carbohydrate contents were determined by the high-performance liquid chromatography (HPLC-RI) method. There are statistically proven differences in the content of individual carbohydrates depending on the sampling area of chestnuts. Potassium has a significant presence in sweet chestnuts as a mineral substance. Its content was determined in the 377–789 mg/100 g DW range. The content of sodium (calcium, magnesium, and phosphorus) was 0.65–6.90 (26.9–103, 58.7–101, and 96.5–179) mg/100 g DW. The contents of mineral substances were determined by the AAS method. The content of carbohydrates and mineral substances is mainly influenced by variety and age.

Leek (Allium porrum L.), a commonly grown vegetable widely used in the food industry, has gained increased interest in recent years in connection with its content of bioactive substances. Therefore, this study aimed to determine and evaluate the influence of cultivar and morphological part on the total content of polyphenols, sulfur compounds, and the antioxidant activity in the monitored morphological parts of leek (Allium porrum L.). The total polyphenol content (TPC) in the white part of analyzed leek cultivars ranged from 446.30 to 1580.55 mg GAE.kg-1 DM. TPC in the green part of analyzed leek cultivars ranged from 748.09 to 2172.78 mg GAE.kg-1 DM. TPC in the leaves of analyzed leek cultivars ranged from 2301.24 to 5477.73 mg GAE.kg-1 DM. The antioxidant activity (AA) in the white part of analyzed leek cultivars ranged from 3.70 to 14.23 mmol TE.kg-1 DM. AA in the green part of analyzed leek cultivars ranged from 6.89 to 14.38 mmol TE.kg-1 DM. AA in leaves of analyzed leek cultivars ranged from 30.85 to 106.92 mmol TE.kg-1 DM. The total sulfur content (TSC) in the white part of analyzed leek cultivars ranged from 0.25 to 0.52 %. TSC in the green part of analyzed leek cultivars ranged from 0.27 to 0.52 %. TSC in the leaves of analyzed leek cultivars ranged from 0.31 to 0.59 %. Based on the analysis of variance, we can state that statistically higher (p< 0.05) TPC, AA, and TSC were determined in the leaves of the leek. Statistically higher (p< 0.05) TPC, AA, and TSC in all morphological parts were determined in the cultivar De Carentan. The results confirmed the variability of bioactive substances and antioxidant activity in the individual monitored cultivars, but also in the monitored morphological parts of the leek.

The Horehronie region belongs to the oldest industrial areas in Slovakia. It is contaminated by residual acid tar dumps from times of Petrochema Dubová factory production since 1964. In the presented study, heavy metals (Cu, Cd, Ni, Zn, Pb) were determined in soils and forest fruits (Vaccinium myrtillus L., Vaccinium vitis-idaea L., Fragaria vesca L., Rosa canina L., Rubus idaeus L.) collected over two years from five locations in the Horehronie using Flame AAS method (Zn, Cu, Ni) and Graphite Furnace AAS method (Cd, Pb). The cadmium content, which was higher than its limit value in all analysed soils, poses the biggest threat. We determined more than 20 times the limit value for cadmium in the sample Veľká Smrekovica (9.17 mg/kg).The contamination factor (Cf) values and the geoaccumulation index (Igeo) indicate that this hazardous metal is involved in soil contamination to a large extent. The highest values of the degree of contamination (Cdeg) and the pollution load index (PLI) were determined in samples from the Ždiarska dolina and the Veľká Smrekovica. The contents of nickel and zinc were higher than the limit values only in the 1st sampling year in the Ždiarska dolina sample (46.30 mg/kg; 138.30 mg/kg). The results showed that soil monitoring and remediation of old environmental burdens are important in the territory of the Horehronie region. The highest permissible amounts for cadmium were exceeded in all types of forest fruits (0.03-0.18 mg/kg FW). The contents of nickel and lead were exceeded only in the sample of rosehips (Rosa canina). The contents of zinc and copper were lower than the permissible amounts in all samples. The estimated daily intake (EDI) was lower than the acceptable daily intake of all heavy metals. The bioaccumulation factor (BAF), total hazardous quotient and hazard index of the analysed samples was < 1, which means that the consumption of forest fruits from the Horehronie does not pose a health risk for the consumer.