In this study the leaves and fruits of wild raspberry (Rubus idaeus L.) populations from the central Balkan region were examined to determine the level of secondary metabolites and related antioxidant activity, as well as biological activity, upon existing ethnobotanical evidence, primarily linked to gastrointestinal disorders. The values obtained for total phenols ranged from 59.68 to 96.83 mg GA g-1 and 24.29 to 38.71 mg GA g-1 in leaf and fruit extracts, respectively. The highest values of tannins and anthocyanins were determined for leaf extracts from a population of east Serbia at a level of 1.27 mg mL-1 and 9.00 mg mL-1. Antioxidant activity was evaluated by measuring the scavenging capacity of the extracts on DPPH. Higher antioxidant activity was detected in the leaf extracts than in the fruit extracts. Leaf and fruit extract were the most effective against Escherichia coli (ATCC 8739). Anticancer activity was studied on a human colorectal cancer cell line HCT-116. Leaf extracts exhibited anticancer activity with IC50/24 h 162.38 μg mL-1 and IC50/48 h 95.69 μg mL-1. Wild raspberry leaf and fruit extracts contain numerous secondary metabolites providing marked antioxidant, antimicrobial and anticancer activity.

Variations in abiotic environmental factors have significant effects on quantity and quality of secondary metabolites, which is particularly important for plant species that possess biologically active compounds. The purpose of this study is determination of the total phenolic content, flavonoid concentration, and antioxidant activity of the different parts of Inula helenium L. (Asteraceae) sampled from different populations and in different time periods. The amounts obtained for the total phenolics varied from 16.73 to 89.85 mg of gallic acid (GA)/g. The concentration of flavonoids ranged from 9.32 to 376.22 mg of rutin (Ru)/g. The IC₅₀ values of antioxidant activity determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical method varied from 161.60 to 1563.02 μg/ml. The inflorescence and roots possessed high concentration of phenolic compounds and significant antioxidant activity, while leaves contained the highest concentration of flavonoids. Additionally, the quantity of the phenolics, as well as antioxidant activity, significantly varied among the different populations due to different impacts of environmental factors. This research showed that I. helenium represents an abundant source of bioactive substances, and that the quantity of these compounds greatly differs among the different populations as well as in the same populations regarding the different time periods as well as plant parts.

Many compounds from the phenolic group, flavonoids in particular, are well-known antioxidants, although their role in plant response to stress is debatable. The aim of this study was to determine the variability of the phenolic content and the antioxidant activity of Olea europaea leaf samples from different habitats. The determination included measurement of the total quantity of phenolics, the flavonoid content, as well as the antioxidant activity of the two types of methanolic leaf extracts of O. europaea from several natural habitats in the Mediterranean region (Tunisia, Malta and Montenegro) and from cultivated conditions (France and Serbia). The results showed that both the total quantity of phenols and flavonoids as well as the intensity of antioxidant activity in the two types of extracts largely depended on the type of habitat. The total quantity of phenols and flavonoids was greater in the samples from cultivated plants which demonstrated the significance of certain conditions in terms of the correlation between the intensity of primary and secondary metabolism. However, the values of antioxidant activity in both types of extract were higher in the samples from natural habitats. The results showed that plants from natural habitats contain secondary metabolites with high biological activity. It could be speculated that these active substances play an important role in the adaptation of plants to the stress caused by arid conditions.

The principal aim of this paper is to show the influence of soil characteristics on the quantitative variability of secondary metabolites. Analysis of phenolic content, flavonoid concentrations, and the antioxidant activity was performed using the ethanol and ethyl acetate plant extracts of the species Cichorium intybus L. (Asteraceae). The samples were collected from one saline habitat and two non-saline habitats. The values of phenolic content from the samples taken from the saline habitat ranged from 119.83 to 120.83 mg GA/g and from non-saline habitats from 92.44 to 115.10 mg GA/g. The amount of flavonoids in the samples from the saline locality varied between 144.36 and 317.62 mg Ru/g and from non-saline localities between 86.03 and 273.07 mg Ru/g. The IC₅₀ values of antioxidant activity in the samples from the saline habitat ranged from 87.64 to 117.73 μg/mL and from 101.44 to 125.76 μg/mL in the samples from non-saline habitats. The results confirmed that soil types represent a significant influence on the quantitative content of secondary metabolites. The greatest concentrations of phenols and flavonoids and the highest level of antioxidant activity were found in the samples from saline soil. This further corroborates the importance of saline soil as an ecological factor, as it is proven to give rise to increased biosynthesis of secondary metabolites and related antioxidant activity.

This study represents a comparative analysis of secondary metabolites content, antioxidant, and antimicrobial activity of 24 halophytes from coastal saline habitats of the Balkan Peninsula (Montenegro, Albania, and Greece). Total content of phenolics, flavonoids, tannins, anthocyanins, antioxidant, and antimicrobial activity was determined for dry methanolic (DME) and crude water extracts (CWE) and compared with well-known medicinal plants. The total phenolic content ranged from 13.23 to 376.08 mg of GA/g of DME, and from 33.68 to 511.10 mg/mL of CWE. The content of flavonoids ranged from 12.63 to 77.36 mg of RU/g of DME, and from 12.13 to 26.35 mg/mL of CWE. Total tannins and anthocyanins varied from 0.05 to 2.44 mg/mL, and from 1.31 to 39.81 µg/L, respectively. The antioxidant activity ranged from 1147.68 to 15.02 µg/mL for DME and from 1613.05 to 21.96 µg/mL for CWE. The best antioxidant properties, and the highest content of phenolic compounds, were determined for Polygonum maritimum and Limonium vulgare with values similar to or higher compared to the medicinal plants. Halophytes with significant antimicrobial potential were Limonium vulgare, L. angustifolium, and Artemisia maritima. Some of the analyzed coastal halophytes can be considered rich natural sources of phenolic compounds, with favorable antioxidative and antimicrobial properties.