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Flavonoids are well-known for their many therapeutic and pharmaceutical effects. In this study, we tested the antibacterial activity of 11 flavonoids extracted from some medicinal plants by the agar diffusion method. Then, we measured their antioxidant activity using the DPPH (2,2'-diphenyl-1-picrylhydrazyl) radical assay and we also tested their acute toxicity effect on mice. The results showed that apigenin-7-O-glucoside was more active against the Gram-positive bacteria and quercetin was more active against the Gram-negative ones. Also, quercetin and diosmin showed the best antioxidant activity. Quercetin, apigenin-7-O-glucoside, luteolin-7-O-glucoside and luteolin-3'-O-glucuronide gave the best acute toxicity values. It can be concluded that quercetin was the most interesting compound for all the tested activities. Also, we observed that the presence or the absence of substitutions in flavonoids influenced significantly the results obtained, whereas the substitution type had a low impact.

The genus Centaurea is known to contain a variety of secondary metabolites of various types, especially sesquiterpene lactones and flavonoids, which have been shown to be biologically active [1][2][3].Centaurea lippii L. (Asteraceae), synonyms Volutaria lippii (L.) Cass.; Volutarella lippii (L.) Cass.; Amberboa lippii (L.) DC., is widely distributed in all Mediterranean areas [4]. Previous phytochemical investigation of this species has led to the isolation of sesquiterpene lactones [5]. The present work concerned the phytochemical study of the chloroform and the n-butanolic soluble parts of the aqueous ethanol extract of the leaves and flowers of the Algerian species.Centaurea lippii was collected during the flowering phase in May 1998, in the East of Algeria, and was authenticated by Prof. A. Kaabeche (Biology Department, University of Setif Algeria).Air-dried and powdered leaves and flowers (1267 g) of Centaurea lippii were macerated with EtOH for 24 h three times. After filtration, the filtrates were combined, concentrated at room temperature, and diluted with 800 mL H 2 O. After remove of chlorophyll, the remaining aqueous solution was extracted successively with CHCl 3 , EtOAc, and n-BuOH to obtain the extracts: chloroform (12 g), ethyl acetate (1 g), and n-BuOH (16 g).The chloroform extract was chromatographed on a 70-230 mesh silica gel column eluted with a gradient of chloroformacetone to yield 8 fractions from which the most important compound 1 was isolated and purified by preparative TLC on silica gel using chloroform-acetone-EtOAc (1:1:3) as eluent.The n-BuOH extract was applied to a polyamide SC6 column eluted with a gradient of toluene-MeOH to yield 9 fractions. Three flavonoid glycosides 2-4 contained in several fractions were isolated by preparative TLC using water-MeOHmethyl-ethyl ketone-acetylacetone (13:3:3:1) as solvent. Purification of each compound for spectral analysis was carried out using MeOH over Sephadex LH-20 column [6].The structures were elucidated by IR, UV, 1 H NMR, 13 C NMR, and MS analysis. All these data were in good agreement with the respective literature data [6][7][8][9][10].Compound 1. C 20 H 26 O 7 , mp 143°C. IR spectrum (KBr, Q, cm -1 ): 1759 (J-lactone), 1705 (C=O conjugated ester), 3356 (-OH). 1 H NMR (250 MHz, CDCl 3 + 2 drops of CD 3 OD, G, ppm, J/Hz): 4.78 (1H, m, H-1), 2.20 (1H, m, H-2), 2.25 (1H, m, H-2c), 2.55 (1H, m, H-3), 2.00 (1H, m, H-3c), 4.81 (1H, d, J 5-6 = 9.7, H-5), 5.25 (1H, t, J 6-5 = J 6-7 = 9.7, H-6), 3.12 (1H, m, H-7), 5.15 (1H, m, H-8), 2.50 (1H, m, H-9), 2.55 (1H, m, H-9c), 5.67 (1H, d, J 13-7 = 2.7, H-13), 6.14 (1H, d, J 13c-7 = 3.3, H-13c), 1.47 (1H, s, H-14), 3.99 (1H, d, J 15-15c = 13.9, H-15), 4.23 (1H, d, J 15c-15

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Background Anvillea garcinii Coss. & Durieu (Anv) plant is used as a traditional North African medicine against several diseases associated with inflammation. At inflammatory sites, reactive oxygen species (ROS) produced in excess by activated phagocyte NADPH oxidase (NOX2) can accentuate inflammatory responses. Thus, we investigated if Anv-water soluble polysaccharides could modulate primary human neutrophil oxidative burst in vitro.MethodsHuman neutrophils were isolated from fresh whole blood and O2 .- generation was measured by cytochrome c reduction assays. Western blots were used to analyse the translocation of PKC, p47phox (a key component of NOX2 activity) to neutrophil plasma membrane. Also, myeloperoxidase (MPO) release in the extracellular medium was studied by western blots. Flow cytometric analysis was used to detect CD11b membrane expression.ResultsWater soluble polysaccharides from Anv dose-dependently inhibited N-formyl-methionyl-leucyl-phenylalanine (fMLF)- and phorbol myristate acetate (PMA)-induced O2 .- generation by human neutrophils. Moreover, Anv-polysaccharides strongly inhibited PMA-induced PKCβ and p47phox translocation to membranes and p47phox phosphorylation on Ser328, a main PKC target. In contrast, polysaccharides extract from Zygophyllum gaetulum plant, which is also used as a traditional North African medicine against inflammatory diseases, was ineffective on this PKCβ-p47phox pathway. Further, Anv inhibited important neutrophil degranulation markers corresponding to myeloperoxidase (MPO) release and CD11b membrane expression.ConclusionThe process of down-regulating NADPH oxidase by polysaccharides extracts from Anv provides new insights into the mechanism of Anv’s anti-inflammatory actions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12906-016-1411-7) contains supplementary material, which is available to authorized users.