which is 4 to 7 cm long. Tepals are usually of different shades of yellow and less frequent of violet or purple colour. The outer tepals have multicellular coloured hairs (so called "beard"). Plants bloom very early in the spring, in March and April. Its distribution area is limited to the Croatian part of the Mediterranean areacentral Dalmatia, the surroundings of the cities of Drniš, Unešić, Zadar, Šibenik and Split, as well as the nearby islands (e.g. Vir, Čiovo, Brač, Kornati etc.). Populations of I. adriatica are generally small, and in the past few years, some of them have disappeared or decreased. For this reason, I. adriatica belongs to the NT (near threatened) IUCN category in the Croatian Red Book of Vascular Plants (Nikolić 2017). However, the plant is suitable for cultivation in greenhouses and in vitro (Vršek et al. 2004; Kereša et al. 2009), and therefore, besides an ornamental use, it has a good perspective to become a useful medical plant, as it was shown for some other Iris taxa (Kukula-Koch et al. 2015; Venditti et al. 2017).
Rhodiola rosea has been used in folk medicine as ethanolic macerates for a long time. This study aims to provide a quantitative and qualitative analysis and comparison of different ethanolic Rhodiola rosea rhizome macerates (35%, 70%, and 96% v/v) and accelerated solvent extraction (ASE) extracts prepared with 85% methanol, in order to shed light on the effectivity of different extraction methods. Extract samples were analyzed by UHPLC-DAD-ESI-MS n on a ZORBAX SB-C18 column (100 × 2.1 mm, 1.8 µm) with a mobile phase consisting of water + 0.1% formic acid and acetonitrile. Qualitative analysis lead to the tentative identification of 18 compounds: Two cyanogenic glycosides (rhodiocyanoside A, lotaustralin), three phenylethanoids (salidroside, viridoside, 2-phenylethyl-vicianoside), two procyanidin and catechin derivatives (epigallocatechin-epigallocatechin gallate, epigallocatechin-3-O-gallate), five phenylpropanoids (cinnamyl alcohol, rosarin, rosavin, rosin, cinnamyl-(6'-O-β-d-xylopyranosyl)-O-β-glucopyranoside), two monoterpene alcohols (rhodioloside E, rosiridin) and four flavonols (rhodionidin, rhodiosin, rhodionin, kaempferol). Quantity was determined for salidroside, cinnamyl alcohol and its three major glycosides (rosarin, rosavin, rosin), as well as three flavonols (rhodionidin, rhodiosin, rhodionin). Methanolic ASE proved to be the superior extraction method for different substance groups. For macerates, high ethanol content increased yield and lowered hydrolysis of glycosides during extraction, but ethanolic macerates still showed low reproducibility and high fluctuations in quantity of marker compounds salidroside and rosavins, as well as flavonols. Rhodiola rosea rhizomes of wild origins seemed to underly great variability in chemical composition dependent on grow site.
Antibiotic resistance is a growing problem and may become the next major global health crisis if no timely actions are taken. Mycobacterial infections are widespread and, due to antibiotic resistance, also hard to treat and a major cause of mortality. Natural compounds have the potential to increase antibiotic effectiveness due to their resistance modulatory and antimicrobial effects. In this study, Peucedanum ostruthium extracts, fractions, and isolated compounds were investigated regarding their antimicrobial and resistance-modulatory effects as well as efflux pump inhibition in Mycobacterium smegmatis. P. ostruthium extracts were found to have anti-mycobacterial potential and resistance modulating effects on ethidium bromide activity. The major antibacterial effect was attributed to ostruthin, and we found that the more lipophilic the substrate, the greater the antimicrobial effect. Imperatorin caused potent modulatory effects by interfering with the action of the major LfrA efflux pump in M. smegmatis. The plant P. ostruthuim has a complex effect on M. smegmatis, including antibacterial, efflux pump inhibition, resistance modulation, and membrane permeabilization, and its major constituents, ostruthin and imperatorin, have a distinct role in these effects. This makes P. ostruthium and its coumarins promising therapeutics to consider in the fight against drug-resistant mycobacteria.
Reynoutria japonica Houtt. is a critical invasive alien plant in Europe and North America with a drastic impact on native flora. However, R. japonica has medicinal potential, especially as a source of stilbenes. In order to explore the potential of simple extractions of R. japonica, we conducted qualitative and quantitative analyses of fresh R. japonica rhizome infusion, decoction, and macerates with ethanol by UHPLC-DAD-ESI-MSn and UHPLC-DAD, with a focus on major constituent groups of stilbenes and anthranoids. Since R. japonica rhizome extracts showed antimicrobial potential in the past, we also evaluated the antimycobacterial effect of raw R. japonica extracts for the first time against Mycobacterium smegmatis. Of thirty-four characterized substances, six were stilbenes and twelve anthranoids. The main constituents, four trans-stilbenes and eight anthranoids, were quantified in a validated UHPLC-DAD method. The 38% ethanol macerate showed high stilbene (155.078 mg/100 g fluid extract) and low anthranoid content (5.420 mg/100 g fluid extract), while decoction showed the highest anthranoids. Antimycobacterial testing gave good results for all macerates (MIC 256 µg/mL) and trans-resveratrol (64 µg/mL). Extraction and enrichment of stilbenes from fresh plant material by simple extraction methods with food-grade solvents might encourage consideration of wild harvest of rhizomes over classic means of eradication of R. japonica.
Little is known about the pharmacological activities of Iris adriatica (Iridaceae), a plant endemic to Dalmatia (Croatia). We therefore performed a bioassay-guided fractionation including high-performance counter current chromatography (HPCCC) and antibacterial tests using Mycobacterium smegmatis mc2 155. One obtained fraction was found to be antimycobacterially active with a MIC of 64 mg L−1. Furthermore, fractions were tested for resistance modulatory effects using ethidium bromide as substrate. We were able to identify the pure isoflavonic compounds irigenin and irilone and a fraction containing mainly benzophenone 2,4,6-trihydroxy-4-methoxy-benzophenone, responsible for the resistance-modulatory activity of this plant.
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