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Seaweed phytosterols are associated with potential health benefits, affording them and the seaweeds that produce them commercial interest. However, little is known about how their production is affected by the cultivation environment, limiting the efficiency with which these compounds can be exploited. Therefore, we performed a pilot study on the effect of nutrient availability and light stress on the sterol content of Saccharina latissima, a rapid growing brown alga of increasing interest in western mariculture. Individuals of S. latissima were subjected to a nutrient-replete and nutrient-depleted regime for 5 weeks, followed by the introduction of light-limited and light-saturated conditions in the sixth week; sampling occurred each week. No significant inter-treatment differences were found in the sterol content in week 1–5. However, significant intra-treatment differences were found in weeks 3–5 regardless of nutrient treatment, wherein the fucosterol, 24-methylenecholesterol, and squalene contents of both treatment groups were found to correlate inversely with photosynthetic performance. Factorial treatment of differential nutrient availability and light stress resulted in marked differences between the sterol content of all groups in week 6. Here, squalene and cycloartenol increased in concentration with increasing irradiance regardless of nutrient treatment. Concentrations of all other sterolic components increased with increasing irradiance and low nutrient conditions while decreasing or remaining unchanged with increasing irradiance and high nutrient conditions. Our data shows that within our cultivation conditions and time frame, the sterol content of S. latissima is unaffected by nutrient availability alone but changes with combined alterations in irradiance and nutrient availability. Graphical abstract

Assessing the umami taste of seaweed on a chemical level can inform the use and selection of seaweed in European cuisine. Accordingly, we developed a method for the simultaneous extraction, separate clean-up and analysis of 21 free amino acids and 10 free nucleotides by reversed phase and mixed-mode HPLC respectively. Of multiple mouth emulating solvents, extracting in Milli-Q at 35 °C was found most suitable. This method showed good linearity (R2 > 0.9996), resolution (Rs ≥ 1.5) and picomole detection limits, and was successfully applied to determine the Equivalent Umami Concentration (EUC) and Taste Activity Values (TAV) of seven Dutch seaweed species. Phaeophyceae showedthe highest EUC, followed by Chlorophyceae and Rhodophyceae (≈ 9.5, 3.7 and 1.1 g/100 g respectively). Glutamic acid always exceeded the TAV, while other umami compounds were species specific. Our method can accurately predict umami intensity and therefore contributes towards species selection for the European palette.

Detailed knowledge on natural dyes is important for agronomy and quality control as well as the fastness, stability, and analysis of dyed textiles. Weld (Reseda luteola L.), which is a source of flavone-based yellow dye, is the focus of this study. One aim was to reduce the required amount of dyed textile to ≤50 μg for a successful chromatographic analysis. The second aim was to unambiguously confirm the identity of all weld flavones. By carrying out the extraction of 50 μg dyed wool with 25 μL of solvent and analysis by reversed-phase UHPLC at 345 nm, reproducible chromatographic fingerprints could be obtained with good signal to noise ratios. Ten baseline separated peaks with relative areas ≥1% were separated in 6 min. Through repeated polyamide column chromatography and prepHPLC, the compounds corresponding with the fingerprint peaks were purified from dried weld. Each was unequivocally identified, including the position and configuration of attached sugars, by means of 1D and 2D NMR and high-resolution MS. Apigenin-4′-O-glucoside and luteolin-4′-O-glucoside were additionally identified as two trace flavones co-eluting with other flavone glucosides, the former for the first time in weld. The microextraction might be extended to other used dye plants, thus reducing the required amount of precious historical textiles.

Madder, used as a red dye, contains anthraquinones, and some of these can react with DNA possibly causing mutagenic effects. This is especially true for 1,3-dihydroxyanthraquinones with a hydroxymethyl (e.g., lucidin 6, ibericin 10) or methyl group (e.g., rubiadin 9) at C-2. In this research, a new process was developed through which the concentration of mutagenic compounds is minimized by adapting extraction and fractionation parameters. The process was tested on lab scale but also on 5000 L industrial scale. The first step is the key biotechnological step. Roots are stirred in water and the concentration of lucidin 6 is reduced to (near) zero by endogenous enzymes. When lucidin 6 is absent, the formation of mutagenic ibericin 10 by a reaction with ethanol as extraction solvent, is not possible. Mutagenicity can be further reduced by heat treatment, which is common in industrial downstream processing, e.g., in spray drying. Removal of rubiadin 9 is possible by flash chromatography. All madder root fractions were tested in the Salmonella microsome assay (Ames test, TA100) for mutagenicity, which was correlated with the anthraquinone concentration.

The main colouring compounds of the dye plant weld (Reseda luteola L.) are the flavones luteolin (lut), lut-7-O-glucoside and lut-7,3ʹ-O-diglucoside. Alum (an aluminium salt)-premordanted wool dyed with weld leads to yellow colours that are of low resistance to light. The photo-stability of lut in aerated methanol–water 8:2 (v/v) solution upon irradiation with light above 300 nm was studied at different lut–Al3+ ratios. Experiments using extracts of weld to dye wool premordanted with increasing quantities of aluminium salts were also carried out. The photo-stability of lut in the polar protic solvent and the photo-resistance (light-fastness) of the colour of weld-dyed wool decrease with increasing concentrations of aluminium ions. Thus, the lower the [Al3+] used for mordanting the wool, the more light-fast its colour. Lowering the [Al3+] appears to have no negative influence on the wash-fastness of the colour. As the gain in light-fastness by the use of low [Al3+] to premordant the wool is not extensive, however, this does not seem to be a way to meet today's requirement of light-fastness of the colours of dyed textiles by itself. Nevertheless, it may be part of a bigger strategy to address the need for increased light-fastness of the colour of wool dyed with weld. Implementation of this approach by dyers is expected to clarify whether it results in benefits for textile dyeing practice.

This paper reports on the colorimetric properties of natural dyes from madder and weld plants. For both crops, a comparison is made among several individual dye compounds and the total plant extracts. Dyeing properties, colour properties and colour stability have been studied. Insight has been gained into the role of the major dye compounds present in the plant. For madder as well as for weld, the use of the total plant extract is considered to be advantageous over the use of individual dye compounds in terms of solubility, colour tone and stability towards light, and non-coloured components present in the plant extract are considered to be responsible for increasing the solubility and the stability of the dye compounds.

This experiment exposes second-year undergraduate students taking a course in analytical organic chemistry to high-performance liquid chromatography (HPLC) and quantitative analysis using the internal standard method. This is accomplished using the real-world application of natural dyes for textiles. The extracted flavonoids of the plant weld are responsible for the yellow color of the dyed wool. Dried and ground weld is extracted for dyeing wool and quantifying the plant’s three main flavonoids. The students also mimic the work of chemists investigating historical textiles by carrying out a small-scale extraction of the dyed wool. Twenty-one students carried out the experiment, and their samples were analyzed using either a traditional 5 µm-particle size HPLC column or a modern 1.8 µm-particle size ultrahigh-pressure liquid chromatography (UHPLC) column mounted in a conventional HPLC system.

In the past decades, there has been a renewed interest in the use of natural dye plants for textile dyeing, e.g. Reseda luteola (weld). Its main yellow dye constituents are the flavones luteolin-7,3'-O-diglucoside, luteolin-7-O-glucoside and luteolin. The aim of this work was to develop a simple validated industrially usable quantitative method to assess the flavone content of R. luteola samples. The flavones were overnight extracted from the dried and ground aerial parts of the plant at room temperature via maceration with methanol-water 8:2. Afterwards, they were quantified through internal standardisation against chrysin by RP-HPLC-UV at 345 nm. The efficiency of the one-step extraction was 95%. The limits of detection (LOD) and quantitation (LOQ) were ≤ 1 ng and ≤ 3 ng, respectively, providing ample sensitivity for the purpose. The precision expressed as relative standard deviation of the entire method was

An analytical method for the comparison of the content of chlorophylls and their structurally similar breakdown products in weld is described.

Direct and indirect HPLC-UV methods for the quantitative determination of anthraquinones in dried madder root have been developed, validated and compared. In the direct method, madder root was extracted twice with refluxing ethanol–water. This method allowed the determination of the two major native anthraquinone glycosides lucidin primeveroside and ruberythric acid. In the indirect extraction method, the anthraquinone glycosides were first converted into aglycones by endogenous enzymes and the aglycones were subsequently extracted with tetrahydrofuran–water and then analysed. In this case the anthraquinones alizarin, purpurin and nordamnacanthal may be determined. The content of nordamnacanthal is proportional to the amount of lucidin primeveroside originally present. The indirect extraction method is easier to apply. Different madder cultivars were screened for their anthraquinone content. Copyright © 2004 John Wiley & Sons, Ltd.

For the production of a commercially useful dye extract from madder, the glycoside ruberythric acid has to be hydrolysed to the aglycone alizarin which is the main dye component. An intrinsic problem is the simultaneous hydrolysis of the glycoside lucidin pritneveroside to the unwanted mutagenic aglycone lucidin. Madder root was treated with strong acid, strong base or enzymes to convert ruberythric acid into alizarin and the anthraquinone compositions of the suspensions were analysed by HPLC. A cheap and easy method to hydrolyse ruberythric acid in madder root to alizarin without the formation of lucidin turned out to be the stirring of dried madder roots in water at room temperature for 90 min: this gave a suspension containing pseudopurpurin, munjistin, alizarin and nordamnacanthal. Native enzymes are responsible for the hydrolysis, after which lucidin is converted to nordamnacanthal by an endogenous oxidase. Copyright ©, 2003 John Wiley & Sons, Ltd.

The roots of Rubia tinctorum L. (madder) are the source of a natural dye. In this review for the first time all the different information on Rubia tinctorum available in the literature is summarised. The dye components are anthraquinones whichprobably contribute to the resistance of the plant against fungi in the soil. Madder roots have been used to dye textiles in many parts of the world since ancient timesand an overview of the historical development, cultivation, harvesting and dyeing techniques of madder is given. The anthraquinone alizarin, the hydrolysis product of ruberythric acid, is supposed to be the main dye component of Rubia tinctorum . The chemical synthesis of alizarin and the biosynthesis of the anthraquinones in Rubia tinctorum are described. As far as the purification, structure elucidation and structures of isolated compounds are concerned, the review confines itself to the anthraquinones of madder. Finally the pharmacology and medicinal uses of madder and pure anthraquinones are discussed. This review supplements and updates earlier partial reviews on madder or anthraquinones by Schweppe, Thomson and Wijnsma.

A HPLC method has been developed for the simultaneous characterisation of anthraquinone glycosides and aglycones in extracts of Rubia tinctorum L. The anthraquinones are separated on an end-capped C18-RP column with a water–acetonitrile gradient as eluent and measured with UV detection at 250 nm. With this method the glycosides lucidin primeveroside and ruberythric acid and the aglycones lucidin, alizarin, purpurin, quinizarin and 2,6-dihydroxyanthraquinone can be analysed. Lucidin which is not commercially available was synthesised starting from resorcinol and phthalic anhydride. The glycosides ruberythric acid and lucidin primeveroside are commercially available as a mixture and were separated by droplet counter-current chromatography in ascending flow with chloroform–methanol–water as eluents prior to their use as standards.