Isatis tinctoria L. (Brassicaceae), which is commonly known as woad, is a species with an ancient and well-documented history as an indigo dye and medicinal plant. Currently, I. tinctoria is utilized more often as medicinal remedy and also as a cosmetic ingredient. In 2011, I. tinctoria root was accepted in the official European phytotherapy by introducing its monograph in the European Pharmacopoeia. The biological properties of raw material have been known from Traditional Chinese Medicine (TCM). Over recent decades, I. tinctoria has been investigated both from a phytochemical and a biological point of view. The modern in vitro and in vivo scientific studies proved anti-inflammatory, anti-tumour, antimicrobial, antiviral, analgesic, and antioxidant activities. The phytochemical composition of I. tinctoria has been thoroughly investigated and the plant was proven to contain many valuable biologically active compounds, including several alkaloids, among which tryptanthrin, indirubin, indolinone, phenolic compounds, and polysaccharides as well as glucosinolates, carotenoids, volatile constituents, and fatty acids. This article provides a general botanical and ethnobotanical overview that summarizes the up-to-date knowledge on the phytochemistry and biological properties of this valuable plant in order to support its therapeutic potential. Moreover, the biotechnological studies on I. tinctoria, which mainly focused on hairy root cultures for the enhanced production of flavonoids and alkaloids as well as on the establishment of shoot cultures and micropropagation protocols, were reviewed. They provide input for future research prospects.

For many years reactive oxygen and nitrogen species (ROS and RNS) have been recognized as key messengers in the process of thiol-based redox regulation. Relatively recently, literature reports began to mention reactive sulfur species (RSS) and their role in thiol regulation. This review is focused on biogenesis and biological properties of RSS, including: hydropersulfides, polysulfides and hydrogen sulfide (H₂S). Based on the most up-to-date literature data, the paper presents biological significance of S-sulfhydration process. In this reaction, sulfane sulfur is transferred to the–SH groups forming hydropersulfides. Protein cysteine residues, called ‘redox switches’ are susceptible to such reversible modifications. In line with the most recent reports, it was emphasized that sulfane sulfur-containing compounds (mainly hydrogen persulfides and polysulfides) are real and better mediators of S-sulfhydration-based signalling than H₂S. We also overviewed proteins participating in the formation and transport of RSS and in mitochondrial H₂S oxidation. In addition, we reviewed many reports about proteins unrelated to sulfur metabolism which are modified by S-sulfhydration that influences their catalytic activity. We also addressed the problem of the regulatory function of S-sulfhydration reaction in the activation of K_ATP channels (vasorelaxant) and transcription factors (e.g. NF_κB) as well as in the mechanism of therapeutic action of garlic-derived sulfur compounds. Some aspects of comparison between RNS and RSS are also discussed in this review.

Methanolic extracts from in vitro grown Scutellaria lateriflora shoots cultured on five Murashige and Skoog (MS) medium variants supplemented with different combinations of 6-benzylaminopurine (BAP) and α-naphthaleneacetic acid (NAA) under different light conditions (monochromatic light, white light and no light) were analysed by HPLC for three groups of metabolites: flavonoids (26 compounds), phenolic acids and their precursors (19+2) and phenylethanoid glycosides (2). The analyses revealed the presence of baicalein, baicalin, wogonin, wogonoside, 3,4-dihydroxyphenylacetic acid and verbascoside. There was clear evidence of the influence of plant growth regulators and light conditions on the accumulation of the analysed groups of secondary metabolites. The amounts of the compounds changed within a wide range—for the total flavonoid content, 30.2-fold (max. 1204.3 mg·100 g⁻¹ dry weight (DW)); for 3,4-dihydroxyphenylacetic acid, 5.5-fold (max. 33.56 mg·100 g⁻¹ DW); and for verbascoside, 1.5-fold (169.15 max. mg·100 g⁻¹ DW). The best medium for the production of most of the compounds was the Murashige and Skoog variant with 1 mg l⁻¹ BAP and 1 mg l⁻¹ NAA. For verbascoside, the best ‘productive’ medium was the MS variant supplemented with 0.5 mg l⁻¹ BAP and 2 mg l⁻¹ NAA. The accumulation of the metabolites was stimulated to the greatest extent by blue light, under which the extracts were found to contain the highest total amount of flavonoids and the highest amounts of flavonoid glucuronides, baicalin and wogonoside, as well as of verbascoside. Their amounts were, respectively, 1.54-, 1.49-, 2.05- and 1.86-fold higher than under the control white light.

Agitated shoot cultures of three Hypericum perforatum cultivars: ‘Elixir’, ‘Helos’ and ‘Topas’ were established and maintained on Linsmaier and Skoog (LS) and Murashige and Skoog (MS) media containing varying concentrations (0.1–3.0 mg l⁻¹) of α-naphthaleneacetic acid (NAA) and 6-benzyladenine (BA). In methanolic extracts of the biomass, the amount s of free phenolic acids and cinnamic acid were determined by HPLC. Six of the seventeen compounds analyzed were detected in all the extracts: 3,4-dihydroxyphenylacetic acid, p-coumaric acid, protocatechuic acid, syringic acid, and two depsides—chlorogenic and neochlorogenic acids. The amounts of individual compounds and the total amount of phenolic acids depended on the media variants used and the increases ranged from 1.2- to 15.0-fold and from 1.2- to 1.9-fold, respectively. The maximum total amounts in the biomass of ‘Elixir’, ‘Helos’ and ‘Topas’ were 212, 222, and 191 mg 100 g⁻¹ DW, respectively. The main metabolites in all the cultivars were neochlorogenic acid (max. 118.81 mg 100 g⁻¹ DW) and 3,4-dihydroxyphenylacetic acid (max. 129.29 mg 100 g⁻¹ DW). Three metabolites that also accumulated in high amounts were protocatechuic acid (max. 21.43 mg 100 g⁻¹ DW), syringic acid (max. 23.63 mg 100 g⁻¹ DW) and chlorogenic acid (max. 18.79 mg 100 g⁻¹ DW). The richest s ource of the estimated compounds and hence a potential biotechnological platform were the shoots of ‘Helos’ cultivated on LS and MS media containing low concentrations of NAA and BA (0.1–1.0 mg l⁻¹).