Sina Cosmulescu

HPLC determination of phenolic acids, flavonoids and juglone in walnut leaves.

A high-performance liquid chromatographic method with gradient elution and diode-array detection was developed to quantify free phenolic acids (gallic, vanillic, chlorogenic, caffeic, syringic, p-coumaric, ferulic, sinapic, salycilic, elagic and trans-cinnamic), flavonoids (catechin, epicatechin, rutin, myricetin and quercetin) and juglone in walnut leaves. Chromatographic separation was performed on a Hypersil Gold C18 column (5 µm particle size, 250 × 4.6 mm) and detection was conducted at three different wavelengths (254, 278 and 300 nm) according to the absorption maxima of the analyzed compounds. Validation procedures were conducted and the method was proven to be precise, accurate and sensitive. The developed method has been applied to analyze walnut leaves samples from nine different cultivars, with the same agricultural, geographical and climatic conditions. The experimental results revealed high concentrations of myricetin, catechin hydrate and rutin, and low concentrations of quercetin and epicatechin aglycones. Ellagic acid was established as the dominating phenolic acid of walnut leaves, followed by trans-cinnamic, chlorogenic and caffeic acids. Juglone content varied between 44.55 and 205.12 mg/100 g fresh weight. Significant differences were detected among cultivars for the concentration levels of phenolics.

Seasonal variation of the main individual phenolics and juglone in walnut (Juglans regia) leaves

Abstract Context: Walnut [Juglans regia L. (Juglandaceae)] is a rich source of phenolic compounds, including phenolic acids, naphtoquinones and flavonoids. The increasing interest in the powerful biological activities of plant phenolics has outlined the necessity of determining their content in leaves of different walnut cultivars. Objective: In this study, walnut leaves from walnut cultivars, originating from the same orchard and from the same year of production, were analyzed for their content in ellagic acid, rutin, myricetin and juglone. In addition, the seasonal variation of these major individual phenolics from June to August was determined. Materials and methods: An HPLC method was used for identification and quantification of ellagic acid, rutin, myricetin and juglone contained in the methanol extract of walnut leaves in nine different cultivars grown under the same agricultural, geographical and climatic conditions. Results: Cultivars and sampling date had statistically significant influence on the phenolics contents in walnut leaves. The results showed that ellagic acid, rutin, myricetin and juglone were more abundant in July 15th samples (average content is 84.62 mg/100 g FW, 98.9 mg/100 g FW, 178.09 mg/100 g FW and 73.81 mg/100 g FW, respectively). Their contents increases similarly in all the cultivars; therefore, the walnut leaves should preferentially be collected until early August, when phenolics content is higher. Discussion and conclusion: The results reported here show that genotype and its interaction with the environment could make significant differences in leaf polyphenols. Walnut leaves may become a noticeable source of compounds with health protective potential.

Phenolic acids and flavonoids profiles of extracts from edible wild fruits and their antioxidant properties

ABSTRACT In this study, the total phenolic, total flavonoids, phenolic compounds, the mineral content, and antioxidant activity of fruit extracts of seven wild species (Crataegus monogyna Jacq., Prunus spinosa L., Rosa canina L., Hippophaë rhamnoides L., Rubus fruticosus L., Prunus padus, Cornus mas L.) were investigated. The results indicated significant differences (p < 0.05) in the total phenolics and total flavonoids content, between the seven analyzed species. These ranged from 184.69 to 727.29 mg GAE/100 g FW and 17.27 to –165.55 mg QE/100 g FW, respectively. The antioxidant activity found in fruits was not directly affected by the total phenolic content (TPC). This activity was linked to a larger extent to the type of individual phenolic compounds and to a lesser extent to the TPC, because fruits with higher TPC have not always presented the highest values of antioxidant activity. HPLC analysis of methanolic extract showed the presence of phenolic acids (i.e. gallic, vanillic, chlorogenic, caffeic, syringic, p-coumaric, ferulic, sinapic, salycilic, elagic, and trans-cinnamic) and flavonoids (i.e. catechin, epicatechin, rutin, myricetin, and quercetin). Significant differences (p < 0.05) were observed in each individual mineral between fruits from wild flora. The fruits tissues of wild species turned out to be a good source of calcium (Ca), magnesium (Mg), sodium (Na), iron (Fe), manganese (Mn), copper (Cu), chromium (Cr), zinc (Zn), and boron (B). The results demonstrated that wild species possessed great potential for food production as sources of bioactive compounds such as phenolic compounds and minerals, for food supplements or functional foods.

Optimization of ultrasound-assisted hydroalcoholic extraction of phenolic compounds from walnut leaves using response surface methodology

Abstract Context Walnut leaves are highly appreciated for their pharmacological effects and therapeutic properties which are mainly attributed to their high content of phenolic compounds. Objective This study optimizes ultrasound assisted hydroalcoholic extraction (UAE) of phenolic compounds from dried walnut leaves by the maximization of total phenolics content (TPC) and total flavanoids content (TFC) of the extracts. Materials and methods Optimal conditions with regard to ethanol concentration (X1: 12.17–95.83% v/v), extraction time (X2: 8.17–91.83 min) and liquid-to-solid ratio (X3: 4.96–25.04 v/w) were identified using central composite design combined with response surface methodology. A high-performance liquid chromatography method with diode-array detection was used to quantify phenolic acids (gallic, vanillic, chlorogenic, caffeic, syringic, p-coumaric, ferulic, sinapic, salicylic, ellagic and trans-cinnamic), flavonoids (catechin, epicatechin, rutin, myricetin and quercetin) and juglone in the extracts. Results Liquid-to-solid ratio and ethanol concentration proved to be the primary factors affecting the extraction efficiency. The maximum predicted TPC, under the optimized conditions (61% ethanol concentration, 51.28 min extraction time and 4.96 v/w liquid-to-solid ratio) was 10125.4 mg gallic acid equivalents per liter while maximum TFC (2925 mg quercetin equivalents per liter) occurred at 67.83% ethanol concentration, 4.96 v/w liquid-to-solid ratio and 49.37 min extraction time. High significant correlations were found between antioxidant activity and both TPC (R2 = 0.81) and TFC (R2 = 0.78). Discussion and conclusion Extracts very rich in polyphenols could be obtained from walnut leaves by using UAE, aimed at preparing dietary supplements, nutraceuticals or functional food ingredients.

Phenolic Profile and Antioxidant Capacity of Walnut Extract as Influenced by the Extraction Method and Solvent

Abstract Total phenolic content, total flavonoid content, antioxidant activity and individual phenolic compounds were assessed in full fat and defatted walnut kernel. For quantification of phenolic fraction of walnut kernels, two different solvents (methanol and ethanol) and two methods of extraction (ultrasonic-assisted extraction and Soxhlet extraction) were tested. Total phenolics, flavonoid content and antioxidant capacity of alcoholic extracts varied depending on the solvent used and extraction methods. Seventeen phenolic compounds were detected and the study provides evidence on high phenolic contents and high antioxidant potential of full fat walnut kernel and defatted walnut kernel. The Soxhlet extraction is the best in terms of the amounts of total phenolic content (2,089.2 mg gallic acid equivalent/100 g dry matter), while the ultrasonic assisted extraction is a fast method but resulted in significantly lower phenolic content (667.3–1,426.8 mg gallic acid equivalent /100 g dry matter). The concentrations of phenolics (especially (+)-catechin hydrate, juglone, vanillic acid, caffeic acid, ferulic acid, sinapic acid, salicylic acid and ellagic acid) are many fold lower in ultrasonic-assisted extraction as compare to the Soxhlet method using the same extraction solvent. The results of this study provide evidence on high phenolic contents and high antioxidant potential of full fat and defatted walnut kernel.

Phenological calendar in some walnut genotypes grown in Romania and its correlations with air temperature

Phenology is the study of periodic biological events in the plant world that are influenced by the environment. Temperature increase in spring season can advance the spring phases, but warming in autumn and winter may slow the fulfillment of chilling requirements and lead to later onset of spring events. This study examined different genotypes of walnut trees under environmental conditions, and measured the cold demand, heat requirements, and average time from budburst till flowering for 28 walnut genotypes. The information obtained provides a better understanding of the phenological temperature response of walnuts that will be useful for walnut production and will also contribute to the development of adaptation measures in the light of the expected climate change.