Ana M. L. Seca

Chemical composition and structural features of the macromolecular components of Hibiscus cannabinus grown in Portugal

Different morphological regions of Hibiscus cannabinus plants grown in Portugal were submitted to chemical composition studies. General chemical composition was determined by established methods. The polysaccharides were fractionated by successive extractions of holocellulose with aqueous KOH solutions. The sugar composition was determined by hydrolysis of polysaccharides followed by gas chromatography (GC) analysis of neutral sugars and spectrophotometric determination of uronic acids. In situ lignins and milled wood lignins (MWL) were characterised by permanganate oxidation followed by GC and GC-MS (mass spectrometry) analysis of the methylated oxidation products. The results of general chemical analysis have evidenced the different relative abundance of holocellulose, lignin, proteins, extractives and ashes in bark, core and foliage, at different stages of maturity. About 70–80% of the core hemicelluloses (about 20% o.d. material) was easily extracted with 5% KOH aqueous solutions against 60–70% (about 15% o.d. material) for the hemicelluloses of the bark. This hemicellulose fraction was composed mainly by glucuronoxylans with high content of uronic acids (xylose: uronic acid: 3–5: 1 for bark and 5–10: 1 for core). The hemicellulose fraction extracted with 24% KOH aqueous solutions was composed mainly by glucuronoxylans (80–90%) and glucomannans (10–15%). The results obtained by the permanganate oxidation method indicated that kenaf lignins are H-G-S type with approximate H: G: S molar proportions of (9–13): (55–60): (27–34) in bark and (14–20): (57)-(74): (12–23) in core, which evidences a high content of H and G units and a relatively low content of S units when compared with traditional dicotyledons. The relative proportion of H, G and S units as well as the structural features of lignins depends on the stage of maturity and on the morphological region of the plant. Kenaf lignins present a lower degree of condensation when compared with traditional wood lignins.

Phenolic constituents from the core of Kenaf (Hibiscus cannabinus)

Four lignans, boehmenan H [2-(4-hydroxy-3-methoxyphenyl)-5-[3-(4-hydroxy-3-methoxycinnamoyloxy)propyl]-3-hydroxymethyl-7-methoxybenzodihydrofuran], boehmenan K [2-(4-hydroxy-3-methoxyphenyl)-5-[3-(4-hydroxycinnamoyloxy)-1-propenyl]-3-(4-hydroxy-3-methoxycinnamoyloxymethyl)-7-methoxybenzodihydrofuran], threo-carolignan H [threo-1-(4-hydroxy-3-methoxyphenyl)-2-[4-[3-(4-hydroxy-3-methoxycinnamoyloxy)propyl]-2-methoxyphenoxy]-1,3-propanodiol], and threo-carolignan K [threo-1-(4-hydroxy-3-methoxyphenyl)-3-(4-hydroxy-3-methoxycinnamoyloxy)-2-[4-[3-(4-hydroxycinnamoyloxy)-1-propenyl]-2-methoxyphenoxy]-1-propanol] as well as several other lignans, aldehydes and a tyramine derivative were isolated from the acetone extract of core of kenaf (Hibiscus cannabinus). All the structures were established by spectroscopic methods. The hitherto unreported 13C NMR spectra of some compounds are also presented and discussed. 2D NMR techniques have allowed the revision of certain previously reported 13C NMR assignments of some scarce naturally occurring compounds.

The genus Inula and their metabolites: from ethnopharmacological to medicinal uses.

ETHNOPHARMACOLOGICAL RELEVANCE The genus Inula comprises more than one hundred species widespread in temperate regions of Europe and Asia. Uses of this genus as herbal medicines have been first recorded by the Greek and Roman ancient physicians. In the Chinese Pharmacopoeia, from the 20 Inula spp. distributed in China, three are used as Traditional Chinese medicines, named Tumuxiang, Xuanfuhua and Jinfeicao. These medicines are used as expectorants, antitussives, diaphoretics, antiemetics, and bactericides. Moreover, Inula helenium L. which is mentioned in Minoan, Mycenaean, Egyptian/Assyrian pharmacotherapy and Chilandar Medical Codex, is good to treat neoplasm, wound, freckles and dandruff. Many other Inula spp. are used in Ayurvedic and Tibetan traditional medicinal systems for the treatment of diseases such as bronchitis, diabetes, fever, hypertension and several types of inflammation. This review is a critical evaluation of the published data on the more relevant ethnopharmacological and medicinal uses of Inula spp. and on their metabolites biological activities. This study allows the identification of the ethnopharmacological knowledge of this genus and will provide insight into the emerging pharmacological applications of Inula spp. facilitating the prioritirization of future investigations. The corroboration of the ethnopharmacological applications described in the literature with proved biological activities of Inula spp. secondary metabolites will also be explored. MATERIALS AND METHODS The major scientific databases including ScienceDirect, Medline, Scopus and Web of Science were queried for information on the genus Inula using various keyword combinations, more than 180 papers and patents related to the genus Inula were consulted. The International Plant Name Index was also used to confirm the species names. RESULTS Although the benefits of Inula spp. are known for centuries, there are insufficient scientific studies to certify it. Most of the patents are registered by Chinese researchers, proving the traditional use of these plants in their country. Although a total of sixteen Inula species were reported in the literature to have ethnopharmacological applications, the species Inula cappa (Buch.-Ham. ex D.Don) DC., Inula racemosa Hook.f., Inula viscosa (L.) Aiton [actually the accepted name is Dittrichia viscosa (L.) Greuter], Inula helenium, Inula britannica L. and Inula japonica Thunb. are the most frequently cited ones since their ethnopharmacological applications are vast. They are used to treat a large spectrum of disorders, mainly respiratory, digestive, inflammatory, dermatological, cancer and microbial diseases. Fifteen Inula spp. crude extracts were investigated and showed interesting biological activities. From these, only 7 involved extracts of the reported spp. used in traditional medicine and 6 of these were studied to isolate the bioactive compounds. Furthermore, 90 bioactive compounds were isolated from 16 Inula spp. The characteristic compounds of the genus, sesquiterpene lactones, are involved in a network of biological effects, and in consequence, the majority of the experimental studies are focused on these products, especially on their cytotoxic and anti-inflammatory activities. The review shows the chemical composition of the genus Inula and presents the pharmacological effects proved by in vitro and in vivo experiments, namely the cytotoxic, anti-inflammatory (with focus on nitric oxide, arachidonic acid and NF-κB pathways), antimicrobial, antidiabetic and insecticidal activities. CONCLUSIONS Although there are ca. 100 species in the genus Inula, only a few species have been investigated so far. Eight of the sixteen Inula spp. with ethnopharmacological application had been subjected to biological evaluations and/or phytochemical studies. Despite Inula royleana DC. and Inula obtusifolia A. Kerner are being used in traditional medicine, as far as we are aware, these species were not subjected to phytochemical or pharmacological studies. The biological activities exhibited by the compounds isolated from Inula spp., mainly anti-inflammatory and cytotoxic, support some of the described ethnopharmacological applications. Sesquiterpene lactone derivatives were identified as the most studied class, being britannilactone derivatives the most active ones and present high potential as anti-inflammatory drugs, although, their pharmacological effects, dose-response relationship and toxicological investigations to assess potential for acute or chronic adverse effects should be further investigated. The experimental results are promising, but the precise mechanism of action, the compound or extract toxicity, and the dose to be administrated for an optimal effect need to be investigated. Also human trials (some preclinical studies proved to be remarkable) should be further investigated. The genus Inula comprises species useful not only in medicine but also in other domains which makes it a high value-added plant.

Variations in chemical composition and structure of macromolecular components in different morphological regions and maturity stages of Arundo donax

Arundo donax plants were manually separated into fractions of different morphological regions (internodes, nodes and foliage) at different stages of maturity and submitted to chemical composition studies. General chemical composition was determined by established methods. The polysaccharides were fractionated by successive extractions of holocellulose with aqueous KOH solutions. The sugar composition was determined by hydrolysis of polysaccharides followed by GC analysis of neutral sugars as alditol acetates and spectrophotometric determination of uronic acids. In situ lignins, milled wood lignins (MWL) and dioxane lignin were characterised by permanganate oxidation followed by GC and GC-MS analysis of the methylated oxidation products and by quantitative 13C NMR spectroscopy. The results of general chemical analysis evidenced the different relative abundance of holocellulose, lignin, proteins, extractives and ashes in internodes, nodes and foliage, at different stages of maturity. In internodes, nodes and foliage about 70–80% of hemicelluloses (21–30% o.d. material) were easily extracted with 5% KOH aqueous solutions. The analysis of hemicelluloses indicated that they are constituted mainly by arabinoglucuronoxylans with a xylose:arabinose:uronic acid ratio of 91–93:5–7:2 for internodes. The high content of xylose in Arundo donax stem (24–27% o.d. material) and the easy extraction of hemicelluloses opens new perspectives for the use of this reed as a source of pentosans. The results obtained by the permanganate oxidation method indicated that Arundo donax lignins are essentially H-G-type with approximate H:G:S proportions of (32–36):(59–61):(5–8) in internodes. The H units are constituted mainly by esterified p-coumaric acid. These results were confirmed by quantitative 13C NMR spectroscopy of isolated dioxane lignin. The quantity of condensed structures in in situ lignin decreases from the older to the younger parts of the stems and is much higher in nodes than internodes.

Lignanamides and other phenolic constituents from the bark of kenaf (Hibiscus cannabinus)

Two new acyclic phenylpropane lignanamides, grossamide K and erythro-canabisine H, and the naphthol glucoside 2,5-dimethyl-3-O-beta-D-glucopyranosylnaphthol, along with six known compounds were isolated from the acetone extract of bark of Hibiscus cannabinus. All structures were established by spectroscopic methods including 2D NMR techniques, which allowed the correction of certain previously reported 13C NMR assignments of grossamide.

Chemical composition of the light petroleum extract of Hibiscus cannabinus bark and core

GC/MS studies of the light petroleum extracts obtained from different morphological regions of kenaf (Hibiscus cannabinus) showed large differences between the composition of the bark and of the core. The non-polar lipid constituents were essentially fatty acids (30.7% in bark; 53.3% in core), long chain alcohols (19.3% in bark), alkanes (22.0% in bark), sterols (12.5% in bark; 25.4% in core) and triterpenes (11.2% in bark). Octacosanyl eicosanoate (15.7%) was detected only in the bark extract and was identified by NMR and MS experiments, and by GC/MS after transesterification. Motiol, stigmast-4-en-3,6-dione (both reported here for the first time in the genus Hibiscus), β-sitosterol and stigmast-4-en-3-one were isolated by TLC and their structures confirmed by NMR experiments and by MS. The NMR structural characterisations reported permit the correction of some previously recorded 13C NMR data. Copyright

Isolation and characterization of a lignin-like polymer of the cork of Quercus suber L.

A lignin-like polymer was successfully extracted from the cork of Quercus suber L. using an organosolv-based technique. This material was characterized by elemental analysis, functional group analysis, nitrobenzene oxidation followed by HPLC analysis of the oxidation products, FTIR and liquid 13 C NMR. The evidence thus obtained indicated that the extracted material was composed mainly of a lignin-like polymer covalently bound to residual aliphatic structures which are not present in common lignins and which have been assigned to suberin. The latter is likely to be attached to the oxygenated side chains of the phenolic polymer but bonding through the aromatic ring can also be envisaged. No residual carbohydrates were detected. The phenolic polymer, composed mainly of guaiacyl-type units and small amounts of syringyl-type units, had a low methoxy content and a high degree of condensation. This polymer showed the presence of a fraction containing C 6 C 0 units with n < 3 or even n < 2.

Seaweeds as Preventive Agents for Cardiovascular Diseases: From Nutrients to Functional Foods

Being naturally enriched in key nutrients and in various health-promoting compounds, seaweeds represent promising candidates for the design of functional foods. Soluble dietary fibers, peptides, phlorotannins, lipids and minerals are macroalgae’s major compounds that can hold potential in high-value food products derived from macroalgae, including those directed to the cardiovascular-health promotion. This manuscript revises available reported data focusing the role of diet supplementation of macroalgae, or extracts enriched in bioactive compounds from macroalgae origin, in targeting modifiable markers of cardiovascular diseases (CVDs), like dyslipidemia, oxidative stress, vascular inflammation, hypertension, hypercoagulability and activation of the sympathetic and renin-angiotensin systems, among others. At last, the review also describes several products that have been formulated with the use of whole macroalgae or extracts, along with their claimed cardiovascular-associated benefits.

Lipophilic profile of the edible halophyte Salicornia ramosissima

Salicornia ramosissima J. Woods is considered, in the Iberian Peninsula and France, a gourmet product. Nevertheless, is one of the less studied Salicornia species. In this work, GC-MS was employed to, for the first time; fully characterise the lipophilic profile of S. ramosissima and to assess the effect of natural and extra irrigation in that profile. The obtained data showed esterified and free fatty acids, fatty alcohol, sterols, alkanes and aromatic acid derivatives, being palmitic acid, tetracosanol and octacosanol the most abundant compounds. The extra irrigation increases significantly (P<0.001) the content of esterified lipophilic compounds. Stigmastanol, 24-ethyl-δ(22)-coprostenol, several secondary fatty alcohols and dicarboxylic acids were identified for the first time in Salicornia genus. Several of the detected compounds are known to have health benefits and our results suggest that S. ramosissima should be considered as an important dietary source of lipophilic phytochemicals.

Di- and Sesquiterpenoids from Cystoseira Genus: Structure, Intra-molecular Transformations and Biological Activity

Natural products have been the single most productive source of leads for the development of drugs, because of the great variety of their chemical structures. Previous chemical investigation of members of the genus Cystoseira resulted in the discovery of various bioactive secondary metabolites. The secondary metabolites isolated and characterized are very interesting, both from the biological activity and structural complexity points of view, which make this genus an attractive target for further investigations. The present review covers the research progress on natural products isolated from this genus since January 1995 until now, concerning the isolation and structural elucidation of the secondary metabolites from Cystoseira species. In this contribution significant biological properties are briefly discussed. Simultaneously, we gradually construct an intra-molecular pathway that logically interrelates the isolated compounds.