Impact of Phylogenetically Diverse Bacterial Endophytes of Bergenia pacumbis on Bergenin Production in the Plant Cell Suspension Cultures.

Plant in vitro cultures are potential sources for secondary metabolites. However, low productivity is often a major drawback for industrial application. Elicitation is an important strategy to improve product formation in vitro. In this context, endophytes are of special interest as biotic elicitors due to their possible interaction with the metabolism of the host plant. A total of 128 bacterial endophytes were isolated from the medicinal plant Bergenia pacumbis and taxonomically classified using 16S rRNA gene sequencing. Five strains belonging to different genera were grown in lysogeny broth and tryptic soy broth medium and cells as well as spent media were used as elicitors in cell suspension cultures of B. pacumbis. Production of the main bioactive compound bergenin was enhanced 3-fold (964 µg/g) after treatment with cells of Moraxella sp. or spent tryptic soy broth medium of Micrococcus sp. These results indicate that elicitation of plant cell suspension cultures with endophytic bacteria is a promising strategy for enhancing the production of desired plant metabolites.

Production of bioactive plant secondary metabolites through in vitro technologies-status and outlook.

Medicinal plants have been used by mankind since ancient times, and many bioactive plant secondary metabolites are applied nowadays both directly as drugs, and as raw materials for semi-synthetic modifications. However, the structural complexity often thwarts cost-efficient chemical synthesis, and the usually low content in the native plant necessitates the processing of large amounts of field-cultivated raw material. The biotechnological manufacturing of such compounds offers a number of advantages like predictable, stable, and year-round sustainable production, scalability, and easier extraction and purification. Plant cell and tissue culture represents one possible alternative to the extraction of phytochemicals from plant material. Although a broad commercialization of such processes has not yet occurred, ongoing research indicates that plant in vitro systems such as cell suspension cultures, organ cultures, and transgenic hairy roots hold a promising potential as sources for bioactive compounds. Progress in the areas of biosynthetic pathway elucidation and genetic manipulation has expanded the possibilities to utilize plant metabolic engineering and heterologous production in microorganisms. This review aims to summarize recent advances in the in vitro production of high-value plant secondary metabolites of medicinal importance.Key points• Bioactive plant secondary metabolites are important for current and future use in medicine• In vitro production is a sustainable alternative to extraction from plants or costly chemical synthesis• Current research addresses plant cell and tissue culture, metabolic engineering, and heterologous production.

Exploring Actinobacteria Associated With Rhizosphere and Endosphere of the Native Alpine Medicinal Plant Leontopodium nivale Subspecies alpinum.

The rhizosphere of plants is enriched in nutrients facilitating growth of microorganisms, some of which are recruited as endophytes. Endophytes, especially Actinobacteria, are known to produce a plethora of bioactive compounds. We hypothesized that Leontopodium nivale subsp. alpinum (Edelweiss), a rare alpine medicinal plant, may serve as yet untapped source for uncommon Actinobacteria associated with this plant. Rhizosphere soil of native Alpine plants was used, after physical and chemical pre-treatments, for isolating Actinobacteria. Isolates were selected based on morphology and identified by 16S rRNA gene-based barcoding. Resulting 77 Actinobacteria isolates represented the genera Actinokineospora, Kitasatospora, Asanoa, Microbacterium, Micromonospora, Micrococcus, Mycobacterium, Nocardia, and Streptomyces. In parallel, Edelweiss plants from the same location were surface-sterilized, separated into leaves, roots, rhizomes, and inflorescence and pooled within tissues before genomic DNA extraction. Metagenomic 16S rRNA gene amplicons confirmed large numbers of actinobacterial operational taxonomic units (OTUs) descending in diversity from roots to rhizomes, leaves and inflorescences. These metagenomic data, when queried with isolate sequences, revealed an overlap between the two datasets, suggesting recruitment of soil bacteria by the plant. Moreover, this study uncovered a profound diversity of uncultured Actinobacteria from Rubrobacteridae, Thermoleophilales, Acidimicrobiales and unclassified Actinobacteria specifically in belowground tissues, which may be exploited by a targeted isolation approach in the future.

Flavonoids as chemotaxonomic markers in the genus Drosera.

The botanical classification of the huge genus Drosera remains controversial since long. In the present study, the pattern of major phenolic compounds in ten Drosera species belonging to seven different subgenera and/or sections of the genus was investigated for chemotaxonomic allocation. The composition of flavonoids and ellagic acid derivatives in Drosera adelae, Drosera burmannii, Drosera dielsiana, Drosera hilaris, Drosera montana, Drosera petiolaris, and Drosera pygmaea was elucidated for the first time. The scarce data on these compounds in Drosera binata, Drosera aliciae, and Drosera spatulata were complemented significantly. Detailed LC-DAD-MS, LC-NMR, and offline 1D and 2D NMR analyses resulted in the unambiguous identification of around 40 different substances, three of them (8-hydroxy-luteolin-8-O-arabinopyranoside, tricetin-7-O-xylopyranoside and 8-hydroxytricetin-8-O-arabinopyranoside) being natural products described for the first time. The distribution of the compounds characterized underlines their potential to serve as chemotaxonomic markers in this genus.

Discovery and resupply of pharmacologically active plant-derived natural products: A review.

Medicinal plants have historically proven their value as a source of molecules with therapeutic potential, and nowadays still represent an important pool for the identification of novel drug leads. In the past decades, pharmaceutical industry focused mainly on libraries of synthetic compounds as drug discovery source. They are comparably easy to produce and resupply, and demonstrate good compatibility with established high throughput screening (HTS) platforms. However, at the same time there has been a declining trend in the number of new drugs reaching the market, raising renewed scientific interest in drug discovery from natural sources, despite of its known challenges. In this survey, a brief outline of historical development is provided together with a comprehensive overview of used approaches and recent developments relevant to plant-derived natural product drug discovery. Associated challenges and major strengths of natural product-based drug discovery are critically discussed. A snapshot of the advanced plant-derived natural products that are currently in actively recruiting clinical trials is also presented. Importantly, the transition of a natural compound from a "screening hit" through a "drug lead" to a "marketed drug" is associated with increasingly challenging demands for compound amount, which often cannot be met by re-isolation from the respective plant sources. In this regard, existing alternatives for resupply are also discussed, including different biotechnology approaches and total organic synthesis. While the intrinsic complexity of natural product-based drug discovery necessitates highly integrated interdisciplinary approaches, the reviewed scientific developments, recent technological advances, and research trends clearly indicate that natural products will be among the most important sources of new drugs also in the future.

Lignan formation in hairy root cultures of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter).

A hairy root line of Edelweiss (Leontopodium nivale ssp. alpinum (Cass.) Greuter) was obtained upon transformation with Agrobacterium rhizogenes strain ATCC15834. Elicitation of this line with silver nitrate, sucrose, methyl jasmonate and yeast extract at various concentrations in most cases resulted in a stimulation of lignan biosynthesis. Through elicitation with 6% sucrose the roots accumulated the pharmacologically active lignans leoligin and 5-methoxy-leoligin at levels of 0.0678% and 0.0372%, respectively, without significant growth inhibition. These lignan levels were comparable to those found in intact roots of cultivated Edelweiss. The biotechnological production of leoligin could be an attractive option for the continuous, field culture-independent production of the valuable secondary metabolites leoligin and 5-methoxy-leoligin.

Ethnopharmacological in vitro studies on Austria's folk medicine--an unexplored lore in vitro anti-inflammatory activities of 71 Austrian traditional herbal drugs.

ETHNOPHARMACOLOGICAL RELEVANCE: In Austria, like in most Western countries, knowledge about traditional medicinal plants is becoming scarce. Searching the literature concerning Austria's ethnomedicine reveals its scant scientific exploration. Aiming to substantiate the potential of medicinal plants traditionally used in Austria, 63 plant species or genera with claimed anti-inflammatory properties listed in the VOLKSMED database were assessed for their in vitro anti-inflammatory activity. MATERIAL AND METHODS: 71 herbal drugs from 63 plant species or genera were extracted using solvents of varying polarities and subsequently depleted from the bulk constituents, chlorophylls and tannins to avoid possible interferences with the assays. The obtained 257 extracts were assessed for their in vitro anti-inflammatory activity. The expression of the inflammatory mediators E-selectin and interleukin-8 (IL-8), induced by the inflammatory stimuli tumor necrosis factor alpha (TNF-α) and the bacterial product lipopolysaccharide (LPS) was measured in endothelial cells. The potential of the extracts to activate the nuclear factors PPARα and PPARγ and to inhibit TNF-α-induced activation of the nuclear factor-kappa B (NF-κB) in HEK293 cells was determined by luciferase reporter gene assays. RESULTS: In total, extracts from 67 of the 71 assessed herbal drugs revealed anti-inflammatory activity in the applied in vitro test systems. Thereby, 30 could downregulate E-selectin or IL-8 gene expression, 28 were strong activators of PPARα or PPARγ (inducing activation of more than 2-fold at a concentration of 10µg/mL) and 21 evoked a strong inhibition of NF-κB (inhibition of more than 80% at 10µg/mL). CONCLUSION: Our research supports the efficacy of herbal drugs reported in Austrian folk medicine used for ailments associated with inflammatory processes. Hence, an ethnopharmacological screening approach is a useful tool for the discovery of new drug leads.

Identification of ostruthin from Peucedanum ostruthium rhizomes as an inhibitor of vascular smooth muscle cell proliferation.

Inhibition of vascular smooth muscle cell (VSMC) proliferation is of substantial interest in combating cardiovascular disease. A dichloromethane extract from the rhizomes of Peucedanum ostruthium, a traditionally used Austrian medicinal plant with anti-inflammatory properties, was examined for a putative antiproliferative activity in rat aortic VSMC. This extract inhibited serum (10%)-induced VSMC proliferation concentration dependently. Further identification and biological testing of its major constituents revealed that the coumarin ostruthin (7) is the major antiproliferative substance. In summary, a new bioactivity of P. ostruthium rhizomes is described, and 7 has been identified as the responsible compound.

Identification and quantification of coumarins in Peucedanum ostruthium (L.) Koch by HPLC-DAD and HPLC-DAD-MS.

The rhizomes of Peucedanum ostruthium (L.) Koch (masterwort) are traditionally used in the alpine region as ingredient of liqueurs and bitters, and as a herbal drug. A sensitive and specific high-performance liquid chromatography-diode-array detection-mass spectrometry (HPLC-DAD-MS) method has been developed for the simultaneous identification and quantification of its main coumarins, oxypeucedanin hydrate, oxypeucedanin, ostruthol, imperatorin, osthole, isoimperatorin, and ostruthin. Fast HPLC separation could be achieved on an Acclaim C18 column (150 mm × 2.1 mm i.d., 3 µm) using a mobile phase gradient of acetonitrile-water modified with 0.01% acetic acid. The quantification by HPLC-DAD was performed with imperatorin as external standard and validated to demonstrate selectivity, linearity, precision, and accuracy. The content of the main coumarins was quantitated in various batches of commercial and field-collected rhizomes of Peucedanum ostruthium, as well as in beverages prepared thereof.

Root colonization by symbiotic arbuscular mycorrhizal fungi increases sesquiterpenic acid concentrations in Valeriana officinalis L.

In some medicinal plants a specific plant-fungus association, known as arbuscular mycorrhizal (AM) symbiosis, increases the levels of secondary plant metabolites and/or plant growth. In this study, the effects of three different AM treatments on biomass and sesquiterpenic acid concentrations in two IN VITRO propagated genotypes of valerian ( VALERIANA OFFICINALIS L., Valerianaceae) were investigated. Valerenic, acetoxyvalerenic and hydroxyvalerenic acid levels were analyzed in the rhizome and in two root fractions. Two of the AM treatments significantly increased the levels of sesquiterpenic acids in the underground parts of valerian. These treatments, however, influenced the biomass of rhizomes and roots negatively. Therefore this observed increase was not accompanied by an increase in yield of sesquiterpenic acids per plant. Furthermore, one of the two genotypes had remarkably high hydroxyvalerenic acid contents and can be regarded as a hydroxyvalerenic acid chemotype.

Diosgenin contents and DNA fingerprint screening of various yam (Dioscorea sp.) genotypes.

In addition to the importance of many Dioscorea species (yams) as starchy staple food, some representatives are known and still used as a source for the steroidal sapogenin diosgenin, which, besides phytosterols derived from tall-oil, is an important precursor for partial synthesis of steroids for pharmaceutical research and applications. While in edible yams the diosgenin content should be as low as possible, a high yield of the compound is preferable for cultivars which are grown for the extraction of sterols. In the past, miscalculations and insufficiently precise techniques for quantification of diosgenin prevailed. Therefore we set out to re-evaluate the steroid content of a world collection of Dioscorea species, using leaves as sample material. We optimized diosgenin quantification techniques and fingerprinted the whole collection with the DNA amplification fingerprinting (DAF) technique. Total diosgenin contents ranged from 0.04 to 0.93% of dry weight within the collection. Several Dioscorea cultivars can be characterized via their DAF fingerprint patterns.