HPLC-DAD Analysis to Identify the Phenolic Profile of Rhododendron Honeys Collected from Different Regions in Turkey

In this study, phenolic compounds of Rhododendron honey (also known as mad honey) samples collected from the Black Sea Region were identified using high performance liquid chromatography-diode array detector system. The major phenolic substances in Rhododendron honeys were found to be chlorogenic and coumaric acids with the amounts of 0.11–191.54 mg/kg and 0–82.83 mg/kg, respectively. Gallic and ferulic acids were detected in the most honey samples. Additionally, significant correlations were determined between the phenolic substances. The present study showed that Rhododendron honeys contained higher quantities of phenolic acids than flavonoids. Chlorogenic and coumaric acids were the dominant phenolic substances detected in honey samples.     

Antioxidant Capacity and Phenolic Content of the Aqueous Extract of Commonly Consumed Cucurbits

The antioxidant capacity of commonly consumed cucurbits vegetable was determined by the DPPH, FRAP, Fe³⁺ reducing power, and hydrogen peroxide scavenging assay. The aqueous extract of Luffa cylindrica showed the highest value of phenolic content and antioxidant capacity based on FRAP, Fe³⁺ reducing power, and hydrogen peroxide scavenging assay. However, Laginaria siceraria extract showed the highest flavonoid and DPPH scavenging activities among all three cucurbits used in this study. Phenolic content in aqueous extracts of Luffa cylindrica and Laginaria siceraria was almost equal. Cucurbita maxima exhibited the lowest phenolic, flavonoid content, and exhibited the lowest power of antioxidant scavenging. The antioxidant capacity of cucurbits was significantly correlated (P < 0.05) with the phenolic content of their extracts. The antioxidant capacity of Luffa cylindrica and Laginaria siceraria have also shown a significant correlation (P < 0.05).     

Protective effects of phenolic constituents from Cytisus multiflorus,Lamium album L. and Thymus citriodorus on liver cells

The present study investigated the antioxidant and cytoprotective effects of purified ethanolic extracts of Cytisus multiflorus, Lamium album L. and Thymus citriodorus plants. These extracts showed high antioxidant activity in DPPH and reducing power assays. Using a model of chemical stress induced by potassium dichromate (DK) in human hepatoblastoma HepG2 cells, 50 μg/mL of C. multiflorus, L. album and T. citriodorus extracts decreased the rate of reactive oxygen species (ROS) production by 35%, 26% and 20%, respectively, when exposed to 25 μM of DK. This effect was also observed for the treatment of cells with individual polyphenolic compounds determined in the extracts, or with mixtures prepared with individual polyphenolic compounds simulating the phenolic composition of the extracts. Additionally, the purified ethanolic extracts and the prepared polyphenolic mixtures showed a cytoprotective effect against DK-induced toxicity. The overall results emphasize the contribution of polyphenols in antioxidant and cytoprotective properties of the studied plants.     

Total Antioxidant Activity and Total Phenolic Contents in Different Turkish Eggplant (Solanum Melongena L.) Cultivars

In this study, total water soluble antioxidant activity and phenolic content of 26 eggplant ( Solanum melongena L. ) cultivars were investigated. Total water soluble antioxidant activity of the cultivars varied from 2664 to 8247 μmolTrolox/kg, which is a 3.1-fold difference. Cultivars also showed significant variation for total phenolic contents ranging from 615 to 1376 mg/kg, a 2.2-fold difference. The two traits were significantly correlated and results of this study suggested that breeders can use the information to develop eggplant cultivars with high antioxidant activity.     

Radical Scavenging,Total Antioxidant Capacity,and Antiproliferative Activity of Phenolic Extracts from Extra Virgin Olive Oil by Cultivar ‘Frantoio’

The beneficial health effects of extra virgin olive oil are due to both its high content of monounsaturated fatty acids and its high content of phenolic compounds, which have recently attracted research interest. In this context, the aim of this work was to examine the in vitro antioxidant and antiproliferative activities of the phenolic extract obtained from extra virgin olive oil from O. europea cultivar ‘Frantoio’ (samples 1–4), one of the main varieties cultivated in Italy. The total phenolic content was determined by Folin–Ciocalteu method and instead the phenolic profile was obtained by HPLC coupled to a diode array detector and mass spectrometry. Extra virgin olive oil extracts exhibited high antioxidant activity through different mechanisms of action and these activities are related to the phenolic content. Sample 3 demonstrated the strongest free radical scavenging activity with IC₅₀ value of 56.5 μg/mL. The reducing ability measured with FRAP assay revealed that samples ranged from 91.3 to 156 μM Fe(II)/g. The same interesting trend was observed with Trolox equivalent antioxidant capacity value. Moreover, the virgin olive oils showed a good oxidative stability ranging between 19 to 32 h. Antiproliferative activity evaluated by SRB assay revealed that phenolic extracts from the cultivar ‘Frantoio’ showed a strong antiproliferative activity against CORL-23 cell line with an IC₅₀ value of 14.5 and 55.9 μg/mL for samples 3 and 1, respectively, and these results are comparable to the positive control vinblastine. Overall, these results showed that extra virgin olive oils from the cultivar ‘Frantoio’, may represent an interesting source of phenolic compounds as functional components that could be consumed in diets and/or used for the elaboration of functional food and pharmaceutical industries.     

Assessment of Nutritional and Antioxidant Potential of Selected Vitality Strengthening Himalayan Medicinal Plants

Three Himalayan medicinal plants (Habenaria intermedia, H. edgeworthii, and Roscoea procera), widely used in vitality strengthening Ayurvedic formulations in India, were assessed for nutritional phytochemical constituents, and antioxidant activity. These target species emerged as a good source of minerals and possessed important micro elements. Individually, H. intermedia contained a high content of total phenols, thiamins, tannins, and calcium; R. procera was rich in potassium and iron content; and H. edgeworthii emerged as a good source of sodium. While various antioxidant assays provided evidences on the antioxidant potential of target species, greater antioxidant potential of H. intermedia as compared to the other two species was revealing. This study, therefore, highlighted the possibilities of harnessing nutritional and antioxidant potential of these species.     

Influence of air temperature on drying kinetics and antioxidant potential of olive pomace

This work aims to evaluate the influence of olive pomace drying (a solid by-product of the olive oil industry) on both antioxidant potential and drying kinetics. The two main fractions of olive pomace (pits, PI and pulps + peels, P + P) were characterized by image analysis and density measurement. The drying process was analyzed in experiments carried out at different temperatures (from 50 to 150 °C) and mathematically described from the diffusion and Weibull models. The antioxidant potential of the extracts (ethanol–water 80:20 v/v, 22 ± 1 °C, 170 rpm for 24 h) obtained from the dry product was analyzed by measuring the total phenolic content and antioxidant capacity and the main polyphenols were quantified by HPLC–DAD/MS–MS.     

Pre-bottling use of dehydrated waste grape skins to improve colour,phenolic and aroma composition of red wines

Different dehydrated waste grape skins from the juice industry were added into aged and young red wines as an innovative way of compensating for colour loss before bottling. After addition of grape skins, colour intensity of wines increased a mean 11% and a maximum of 31% with predominance of the red component. Total polyphenols mean increase was 10% with a maximum value of 20%. Analysis of low molecular weight phenolic compounds by HPLC–DAD showed a significant (p < 0.05) content increase of the bioactive compounds gallic acid, (+)-catechin, (−)-epicatechin, and (E)-resveratrol. Anthocyanins content also increased at an average of 50 mg/l. The volatile profile of wines analysed by SBSE–GC–MS was only moderately influenced by the treatments. Mixtures of dehydrated waste grape skins were useful to improve the colour and polyphenol profile of red wines, considering them a useful tool for correcting colour loss before bottling.     

Soymilk phenolic compounds,isoflavones and antioxidant activity as affected by in vitro gastrointestinal digestion

The aim of this research was to evaluate changes in the phenolic compounds, isoflavones and antioxidant activity of soymilk following in vitro gastrointestinal digestion (including dialysis). Gastric digestion significantly influenced the release of bioactive substances from the soymilk matrix, increasing the concentration of total phenolic components (35% as the sum of individuals and 14% by Folin–Ciocalteu [F–C] method), total isoflavone content (22%) and total antioxidant activity (76%). The concentration of all those compounds was reduced significantly in the duodenal fraction in comparison to gastric digestion and their lowest concentration was observed in the dialysed fraction, where phenolic acids were not detected. The bioaccessibility of soymilk phenolic compounds was 15% as the sum of individuals and 20% by F–C assay; isoflavones 36% and constituents with antioxidant activity 27%. Results suggest that most of these compounds were sufficiently available to be absorbed and could contribute health benefits.     

Assessment of the antioxidant potential and fatty acid composition of four Centaurea L. taxa from Turkey

This paper focused on the assessment of antioxidant property and fatty acid composition of four Centaurea species. The antioxidant activity of its methanol extract was evaluated by several in vitro experiments including phosphomolybedum assay, DPPH assay, β-carotene/linoleic acid, ferric and cupric reducing power. Total phenolic and flavonoid contents were also evaluated. The methanol extract of Centaurea pulcherrima var. pulcherrima showed the superior free radical scavenging activity, linoleic acid inhibition capacity, reducing power and also had the highest total phenolic content. A significant relationship between antioxidant capacity and total phenolic components was found. The oils of Centaurea taxa were also analysed for fatty acid concentration by gas chromatography. The principal fatty acids in the species were palmitic acid (23.38–30.49%) and linoleic acid (20.19–29.93%). These findings suggest that the Centaurea species could be used as a potential source of new natural antioxidants and unsaturated fatty acids in food industry, cosmetics and pharmaceutical preparations.