Blackthorn or sloe (Prunus spinosa L.) from the family Rosaceae is a widespread wild plant growing from south--central Europe down to eastern Asia Minor and northwards to Scandinavia in open woodlands and forest margins. Nearly all parts of the plant including fruit, bark, root, leaves and flowers have been used since ancient times for the treatment of various ailments. The blackthorn flowers, which are usually processed by drying and used as tea, syrup, fresh juice or tincture to treat various diseases, may have wide potential applications in food and pharmaceutical industries (1,2). Despite a great potential and the long tradition of use in folk medicine, systematic phytochemical investigations of this plant are still missing. Previous investigations refer mainly to flavonoid SummaryThis research was undertaken to investigate the influence of extraction parameters during microwave-assisted extraction on total phenolic content, total flavonoids, total hydroxycinnamic acids and total flavonols of blackthorn flowers as well as to evaluate the antioxidant capacity by two different methods (2,2-diphenyl-1-picrylhydrazyl free radical scavenging capacity and ferric reducing antioxidant power assays). The investigated extraction parameters were: solvent type and volume fraction of alcohol in solvent (50 and 70 % aqueous solutions of ethanol and methanol), extraction time (5, 15 and 25 min) and extraction temperature (40, 50 and 60 °C) controlled by microwave power of 100, 200 and 300 W. Multivariate analysis of variance (MANOVA) was used to evaluate the differences at a 95 % confidence level (p≤0.05). The obtained results show that aqueous solution of ethanol was more appropriate solvent for extraction of phenolic compounds (total flavonoids, total hydroxycinnamic acids and total flavonols) than aqueous solution of methanol. The amount of phenolic compounds was higher in 70 % aqueous solution of ethanol or methanol, while higher antioxidant capacity was observed in 50 % aqueous solution of methanol. Higher temperature of extraction improved the amount of phenolic compounds and also antioxidant capacity determined by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging capacity assay. Extensive duration of extraction (15-to 25-minute interval) has a significant effect only on the increase of total phenolic content, while specific phenolic compound content and antioxidant capacity were the highest when microwave extraction time of 5 min was applied.

Prunus spinosa L. (blackthorn) is used in traditional medicine as a remedy for various diseases. To establish its anticancer properties, we exposed human liver cancer cells (Hep G2) to a range of blackthorn flower extract concentrations (10-200 µg/mL) and determined cytotoxic activity with the neutral red and kenacid blue methods after 24, 48, and 72 h of incubation. Statistically significant inhibitory effects on Hep G2 cellular proliferation were observed at concentrations above 50 µg/mL (p<0.001–0.05). Cell viability was lower when determined with neutral red than kenacid blue method. In addition, we evaluated antioxidant/prooxidant effects of the blackthorn flower extract by measuring reactive oxygen species (ROS), and the results confirmed its prooxidant behaviour within the applied concentration range. Flow cytometry determined primarily necrotic and apoptotic cell death, which provides additional evidence of its cytotoxic effect on liver carcinoma.

No abstract