Željan Maleš

Antimicrobial activity of Paliurus spina-christi Mill. (Christ's thorn)

Paliurus spina-christi Mill. (Rhamnaceae), also known as Christs thorn, is a perennial thorny shrub of widespread distribution in dry and rocky places in Mediterranean region and Asia. In Croatia, this plant grows along the Adriatic coast and on the islands. Christs thorn is used as a diuretic, against diarrhoea and rheumatism in traditional Croatian herbal medicine. Chemical investigations indicate the presence of the flavonoids isoquercitrin, rutin, hyperoside and quercetin-3-O-triglycoside. No literature could be found in respect of the antimicrobial activity of Paliurus spina-christi. The antibacterial effect of extracts from different plant parts was therefore investigated

Optimization of TLC analysis of flavonoids and phenolic acids of Helleborus atrorubens Waldst. et Kit.

Numerical methods for the evaluation of the separation power of thirteen thin-layer chromatographic systems for splitting a methanolic extract of leaves of Helleborus atrorubens Waldst. et Kit. into 15 compounds (flavonoids and phenolic acids) have been investigated. For this purpose, the following mathematical approaches have been applied: calculation of the information content (I), determination of discriminating power (DP) and formation of clusters and dendrogram. The most suitable chromatographic system for the separation of investigated compounds is ethyl acetate-formic acid-water (65:15:20, v/v/v).

HPTLC determination of flavonoids and phenolic acids in some Croatian Stachys taxa

Stachys is a large genus belonging to the family Lamiaceae. In common with many other representatives of this family, the aerial parts of plants belonging to this genus have been used in folk medicine and phytotherapy for many years. The aim of this work was to determine the amounts of biologically active compounds (flavonoids and phenolic acids) present in seven Croatian Stachys taxa (S. alpina, S. officinalis, S. palustris, S. recta subsp. recta, S. recta subsp. subcrenata, S. salviifolia, and S. sylvatica). This was achieved by establishing an appropriate extraction procedure and by analyzing the samples by HPTLC with densitometric evaluation. Plant extracts and standard solutions of flavonoids and phenolic acids were applied to silica gel 60 F254 HPTLC plates as 10 mm bands. Plates were developed in vertical glass chambers previously saturated with the mobile phase, ethyl acetate—acetic acid—formic acid—water, 100 + 11 + 11 + 26 (v/v). After drying and spraying with NP/PEG reagent, the bands were visualized under short and longwavelength UV light. By use of standard solutions, RF values and fluorescence colors of the investigated compounds were determined. Concentrations of the standard solutions were adjusted to the amounts in the samples and again chromatographed with Stachys samples. The Camag Reprostar 3 Videosystem was used for quantitative evaluation. The compound occurring in most of the samples investigated was found to be chlorogenic acid (it was not present in S. recta subsp. recta only); isoquercitrin, luteolin 7-O glucoside, rutin, and quercitrin were present in several of the samples. Although S. recta subsp. recta did not contain chlorogenic acid, it was found to be richest in the flavonoids whose presence was determined. This HPTLC method was found to be simple and convenient for rapid screening of active compounds and quantification of the investigated flavonoids and phenolic acids in Stachys taxa.

Thin-layer chromatographic analysis of flavonoids, phenolic acids, and amino acids in some Croatian Hypericum taxa

The flowering tops of Hypericum hirsutum, H. montanum, H. perforatum subsp. angustifolium, H. perforatum subsp. perforatum, and H. perforatum subsp. veronense, collected from different locations in Croatia, were investigated to determine their flavonoid, phenolic acid, and amino acid composition. Thin-layer chromatography (TLC) on silica gel was used for separation and identification of the flavonoids and phenolic acids and TLC on cellulose was used for investigation of the amino acids. By use of these procedures ten flavonoids, three phenolic acids, and sixteen amino acids were detected and identified in the samples investigated. The composition of these compounds depended on the taxa investigated and the locality. Spectrophotometric analysis of the flavonoid content indicated that the three subspecies of H. perforatum are richer in flavonoids than H. hirsutum and H. montanum. H. perforatum subsp. perforatum is the richest in flavonoids, phenolic acids, and amino acids. This is the first time these biologically active compounds have been identified in the some Hypericum taxa.

Determination of Flavonoids, Phenolic Acids, and Xanthines in Mate Tea (Ilex paraguariensis St.-Hil.)

Raw material, different formulations of foods, and dietary supplements of mate demands control of the content of bioactive substances for which high performance thin layer chromatography (TLC), described here, presents simple and rapid approach for detections as well as quantification. Using TLC densitometry, the following bioactive compounds were identified and quantified: chlorogenic acid (2.1 mg/g), caffeic acid (1.5 mg/g), rutin (5.2 mg/g), quercetin (2.2 mg/g), and kaempferol (4.5 mg/g). The results obtained with TLC densitometry for caffeine (5.4 mg/g) and theobromine (2.7 mg/g) show no statistical difference to the content of total xanthines (7.6 mg/g) obtained by UV-Vis spectrophotometry. Thus, TLC remains a technique of choice for simple and rapid analysis of great number of samples as well as a primary screening technique in plant analysis.

Application of numerical methods to thin-layer chromatographic investigation of the main components of chamomile (Chamomilla recutita (L.) Rauschert) essential oil

Abstract The efficiency of eleven TLC systems for separating the main components of chamomile essential oil has been tested. The information theory and the methods of numerical taxonomy have been applied for this purpose. The design of the most effective series of chromatographic systems is discussed in terms of discriminating power and mean information content. The series of systems with the highest discriminating power is shown to produce the best overall separations for a large specified population of components of chamomile essential oil. It leads to the identification of an unknown component using a minimum number of systems. It has been established that the most favourable mobile phases for TLC of chamomile essential oil are chloroform–toluene (75:25) and chloroform–toluene–ethyl acetate (65:30:5) mixtures.

Quantitative Determination of Flavonoids and Chlorogenic Acid in the Leaves of Arbutus unedo L. Using Thin Layer Chromatography

The plant species Arbutus unedo shows numerous beneficial pharmacological effects (antiseptic, antidiabetic, antidiarrheal, astringent, depurative, antioxidant, antihypertensive, antithrombotic, and anti-inflammatory). For the medicinal use, standardization of extracts is a necessity, as different compounds are responsible for different biological activities. In this paper, we analyze monthly changes in the content of quercitrin, isoquercitrin, hyperoside, and chlorogenic acid. Methanolic extracts of the leaves are analyzed by HPTLC for the identification and quantification of individual polyphenol, and DPPH test is used to determine antioxidant activity. Based on the results obtained, the leaves should be collected in January to obtain the highest concentrations of hyperoside and quercitrin (0.35 mg/g and 1.94 mg/g, resp.), in June, July, and October for chlorogenic acid (1.45–1.46 mg/g), and for the fraction of quercitrin and isoquercitrin in November (1.98 mg/g and 0.33 mg/g, resp.). Optimal months for the collection of leaves with the maximum recovery of individual polyphenol suggested in this work could direct the pharmacological usage of the polyvalent herbal drugs.

Essential oil of Thymus bracteosus Vis. ex Benth., an Endemic Species of Dinaric Karst

Abstract The essential oils of two samples of Thymus bracteosus Vis. ex Benth. (Lamiaceae) collected in Croatia were examined by GC/MS and GC-FID. The major compounds were germacrene D (29.0%) and β-caryophyllene (13.1%), respectively.

USE OF INFORMATION THEORY AND NUMERICAL TAXONOMY METHODS FOR EVALUATING THE QUALITY OF THIN-LAYER CHROMATOGRAPHIC SEPARATIONS OF FLAVONOIDS AND PHENOLIC ACIDS OF RHAMNI CATHARTICI FRUCTUS

A rational selection of a restricted set from fifteen available chromatographic systems for the separation of flavonoids and phenolic acids identified in the methanolic extract of Rhamni cathartici fructus is discussed. Series of mathematical techniques for the evaluation of solvents and solvent combinations in thin-layer chromatography of flavonoids and phenolic acids have been investigated. The chromatographic systems are classified according to their mutual resemblance by numerical taxonomy techniques. The selection criterion in the groups, obtained by numerical taxonomy classification, is the information content or discriminating power. The numerical taxonomic and information theoretical selection procedures are compared and their respective advantages and disadvantages discussed.

Metabolic profiling of rhizomes of native populations of the strictly endemic Croatian species Iris adriatica

Abstract Iris adriatica Trinajstić ex Mitić (Iridaceae L.) is a strictly endemic taxon from Croatia. It is a rhizomatous dwarf plant from the I. pumila complex with a distribution area limited to the Croatian part of the Mediterranean area, mainly central Dalmatia. The genus Iris is known for its richness in isoflavonoids which also play a significant role in chemotaxonomy and biological activity. Hence, in the current study, different plant batches of I. adriatica collected in early spring of 2016 were analysed for their phytochemical profiles and qualitatively compared. UHPLC-PDA-ESI-MS analyses of methanolic rhizome extracts were performed. Altogether, 36 compounds, representing isoflavonoids (including 6,7-methylendioxy derivatives), benzophenones and xanthones were found as aglycones or in glycosidically bound form to be the main constituent groups of I. adriatica rhizomes. Qualitative results were identical between different batches of plant material from collection sites in central Dalmatia, they differed only in quantity. For some phenolic compounds of I. adriatica, chemotaxonomic relevance was detected.