Flavonoids of Limonium axillare

The chemical composition of the aerial parts' essential oil of Limonium lobatum (L.f.) Chaz. growing wild in Algeria

The Limonium genus (Plumbaginaceae) includes several species of perennial herbs and shrubs belonging to a particular type of halophytes, known as 'recretohalophytes'. Limonium species are widely distributed in the Mediterranean region, mainly in the North-Eastern and Southern countries and several bioactivities have been well documented. In the present study, the chemical composition of the essential oil (EO) of the aerial parts of Limonium lobatum (L.f.) Chaz., a species never chemically previously studied and collected in Algeria, which grows in South Spain, North Africa, and SW Asia, was analysed using GC-MS. The main constituents of the EO were monoterpenes involving eucalyptol (14.21%), β-pinene (8.62%), β-myrcene (8.18%). Among the sesquiterpene compounds β-caryophyllene (8.94%) was the major one. The chemical profile of the EO presented here was compared with the EOs of previously investigated Limonium taxa. Furthermore, a complete literature review on the ethno-pharmacological uses of Limonium species was performed.

Characterization and Antimicrobial Activity of a Halophyte from the Asturian Coast (Spain): Limonium binervosum (G.E.Sm.) C.E.Salmon

The work presented herein deals with the characterization and valorization of a halophyte from the cliffs of the Asturian coast: Limonium binervosum (G.E.Sm.) C.E.Salmon (rock sea-lavender). Its biomass and hydromethanolic extracts were studied by elemental and thermal analysis, infrared spectroscopy and gas chromatography-mass spectroscopy. Tetradecanoic acid/esters and 1,2-tetradecanediol were identified in its flower extract, while the leaf extract was rich in linolenic and linoleic acids and their esters, hexadecanoic acid and its esters, and phytol. Both flower and leaf hydromethanolic extracts contained eicosane, sitosterol and tocopherols in significant amounts. With a view to its valorization, the antimicrobial activity of these extracts was investigated against three apple tree and grapevine phytopathogens. Both the hydroalcoholic extracts and their main constituents, alone or in combination with chitosan oligomers (COS), were tested in vitro. A remarkable antibacterial activity was observed for the conjugated complexes of the flower extract with COS, both against Xylophilus ampelinus (MIC = 250 μg·mL-1) and Erwinia amylovora (MIC = 500 μg·mL-1), and complete inhibition of the mycelial growth of Diplodia seriata was found at concentrations <1000 μg·mL-1. In view of these results, this extremophile plant can be put forward as a promising source of bioactive metabolites.

Chemical and biological investigations of Limonium axillare reveal mechanistic evidence for its antidiabetic activity

Root and bark of Limonium axillare (Forssk) Kuntze are used as antidiabetic remedies in parts of East Africa, but this activity has never been fully investigated. To validate its ethnobotanical use, we compared the chemical and pharmacological profiles of the ethanolic extracts of L. axillare root (REE) and aerial parts (AEE). Administration of REE (500 mg kg-1) reduced streptozotocin-induced hyperglycemia by 44%, restored serum insulin levels, reestablished Glut2 and Glut4 expression and ameliorated pancreatic tissue damage in diabetic rats. In vitro studies revealed a strong radical scavenging effect, α-glucosidase, and α-amylase inhibition activity of REE at IC50 at 25.2, 44.8 and 89.1μg/mL, respectively. HPLC analysis identified ten phenolic compounds in REE with umbelliferone as the major constituents at 10 ± 0.081 mg/g of extract. Additionally, six compounds were isolated from REE including, β-sitosterol-3-palmitate, β-sitosterol, myricetin and gallic acids with two new tetrahydrofuran monoterpenes; 2-isopropyl- 3,4,4, trimethyl-tetrahydrofuran (3), and 2-isopropyl-4-methyl-tetrahydrofuran-3,4 dicarboxylic acid (4), the latter was revealed by molecular docking to be a good ligand to glycerol-3-phosphate dehydrogenase a key enzyme in glycolysis.

[Does the sampling locality influence on the antifungal activity of the flavonoids of Marrubium vulgare against Aspergillus niger and Candida albicans?]

OBJECTIVE

The study was undertaken to determine the effect of the sampling locality on the antifungal activity of the flavonoids extracted from the leaves of Marrubium vulgare L. against two fungal strains; Aspergillus niger ATCC 16404 and Candida albicans ATCC 10231.

MATERIALS AND METHODS

The leaves were collected from three different sampling localities belonging northwest Algeria: Tessala mount, M'sila forest and Ain Skhouna. The flavonoid extraction was carried out by using organic solvents with increasing polarity. A phytochemical screening was performed by staining test tubes. The inhibition diameters were measured by solid medium diffusion method. The minimum inhibitory concentrations were determined by dilution method on solid medium.

RESULTS

The antifungal activity varied significantly (P<0.001) according to the sampling locality of the leaves, the flavonoid extract and its concentration, and the strain fungal type. The inhibition diameters varied between 8.16 and recorded 37.5mm even recording a total inhibition of fungal growth and often exceed those induced marketed antifungals (Amphotericin, Fluconazole, Terbinafine and econazole nitrate). The minimum inhibitory concentrations (MICs) obtained range between 6.25 and 100μg/mL; experiencing strong antifungal inhibition. The phytochemical screening revealed the existence of certain flavonoids classes such as flavans and flavanols which may be responsible of this remarkable antifungal power.

CONCLUSION

The sampling locality of Marrubium vulgare leaves influenced on the antifungal activity of flavonoids. These have proven very good fungistatic and worth valuing in pharmacology.

Antimicrobial activity of flavonoids

Flavonoids are ubiquitous in photosynthesising cells and are commonly found in fruit, vegetables, nuts, seeds, stems, flowers, tea, wine, propolis and honey. For centuries, preparations containing these compounds as the principal physiologically active constituents have been used to treat human diseases. Increasingly, this class of natural products is becoming the subject of anti-infective research, and many groups have isolated and identified the structures of flavonoids possessing antifungal, antiviral and antibacterial activity. Moreover, several groups have demonstrated synergy between active flavonoids as well as between flavonoids and existing chemotherapeutics. Reports of activity in the field of antibacterial flavonoid research are widely conflicting, probably owing to inter- and intra-assay variation in susceptibility testing. However, several high-quality investigations have examined the relationship between flavonoid structure and antibacterial activity and these are in close agreement. In addition, numerous research groups have sought to elucidate the antibacterial mechanisms of action of selected flavonoids. The activity of quercetin, for example, has been at least partially attributed to inhibition of DNA gyrase. It has also been proposed that sophoraflavone G and (-)-epigallocatechin gallate inhibit cytoplasmic membrane function, and that licochalcones A and C inhibit energy metabolism. Other flavonoids whose mechanisms of action have been investigated include robinetin, myricetin, apigenin, rutin, galangin, 2,4,2'-trihydroxy-5'-methylchalcone and lonchocarpol A. These compounds represent novel leads, and future studies may allow the development of a pharmacologically acceptable antimicrobial agent or class of agents.

Additional antiprotozoal constituents fromCuphea pinetorum, a plant used in Mayan traditional medicine to treat diarrhoea

In addition to kaempferol and quercetin already found in the roots from Cuphea pinetorum, bioassay-guided fractionation of the crude extract of the aerial part of this species gave four flavonoid glycosides, quercetin-3-O-alpha-rhamnopyranoside, luteolin-7-O-beta-D-glucopyranoside, apigenin-7-O-alpha-L-rhamnopyranoside and apigenin-7-O-beta-D-glucopyranoside, as well as squalen and beta-sitosterol. In vitro antiamoebic and antigiardial activities of isolated compounds indicated that kaempferol is the principal antiprotozoal agent in C. pinetorum. Based on finding this antiprotozoal inhibitor, flavonoids were studied in order to elucidate structure-activity relationships. These data suggest that kaempferol may play an important role in antidiarrhoeal activity of C. pinetorum.

Assessment of the antibacterial activity of selected flavonoids and consideration of discrepancies between previous reports

Activity of the flavonoids apigenin, baicalin and galangin against sensitive and antibiotic resistant strains of Staphylococculs aureus, Enterococcus faecalis, E. faecium, Escherichia coli and Pseudomonas aeruginosa was investigated. Using an agar dilution assay, galangin was shown to have a minimum inhibitory concentration (MIC) of 25 to 50 microg/mL against all six strains of S. aureus but negligible activity against the othe species. Apigenin displayed only marginal activity against S. aureus and no activity was detected from baicalin. In inhibition curve studies, galangin caused a 100,000-fold decrease in the viability of a growing population of S. aureus NCTC 6571 within the first two hours of treatment. Decreases in viability of S. aureus NCTC 11561 and NCIMB 9968 populations were also observed.

Antimicrobial and antifungal activity of crude extracts and isolated saponins from Astragalus verrucosus

The antimicrobial and antifungal properties of several crude extracts and pure saponins, astraverrucins I-VI, from the aerial parts of Astragalus verrucosus were investigated by the disc diffusion method. Antimycotic activity was observed on more polar extracts, but only one saponin showed an appreciable activity.

A new flavonoid from Limonium axillare

A new flavonol glycoside identified as myricetin 3-O-beta-D-sorboside (1) has been isolated from the leaves of L. axillare. The new compound showed a moderate inhibition of Ehrlich ascites carcinoma cells.