Silk fibroin from the silkworm, Bombyx mori, has excellent properties such as biocompatibility, biodegradation, non-toxicity, adsorption properties, etc. As a kind of ideal biomaterial, silk fibroin has been widely used since it was first utilized for sutures a long time ago. The degradation behavior of silk biomaterials is obviously important for medical applications. This article will focus on silk-based biomaterials and review the degradation behaviors of silk materials.

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The interaction of a quercetin copper(II) complex with DNA was investigated using UV-vis spectra, fluorescence measurement, viscosity measurement, agarose gel electrophoresis, and thiobarbituric acid reactive substances assay. The results indicate that the quercetin copper(II) complex can promote the cleavage of plasmid DNA, producing single and double DNA strand breaks, and intercalate into the stacked base pairs of DNA. Moreover, the complex can induce oxidative DNA damage involving generation of reactive oxygen species such as H(2)O(2) and Cu(I)OOH. In addition, the cytotoxicity experiments carried out with A549 cells confirmed its apoptosis-inducing activity. And we also demonstrate that the levels of survivin protein expression in A549 cells decreased, and that relative activity of caspase-3 increased significantly after treatment with the complex. So our results suggest that the antitumor mechanism of the quercetin copper(II) complex involves not only its oxidative DNA damage with generation of reactive oxygen species but also its specific interaction with DNA.

BackgroundIn Chinese traditional medicine, Agrimonia pilosa Ledeb (APL) exhibits great effect on treatment of type 2 diabetes mellitus (T2DM), however its mechanism is still unknown. Considering that T2DM are correlated with postprandial hyperglycemia and oxidative stress, we investigated the α-glucosidase inhibitory activity and the antioxidant activity of flavonoid compound (FC) and triterpenoid compound (TC) from APL.MethodsEntire plants of APL were extracted using 95% ethanol and 50% ethanol successively. The resulting extracts were partitioned and isolated by applying liquid chromatography using silica gel column and Sephadex LH 20 column to give FC and TC. The content of total flavonoids in FC and the content of total triterpenoids in TC were determined by using UV spectrophotometry. HPLC analysis was used to identify and quantify the monomeric compound in FC and TC. The α-glucosidase inhibitory activities were determined using the chromogenic method with p-nitrophenyl-α-D-glucopyranoside as substrate. Antioxidant activities were assessed through three kinds of radical scavenging assays (DPPH radical, ABTS radical and hydroxyl radical) & β-carotene-linoleic acid assay.ResultsThe results indicate FC is abundant of quercitrin, and hyperoside, and TC is abundant of 1β, 2β, 3β, 19α-tetrahydroxy-12-en-28-oic acid (265.2 mg/g) and corosolic acid (100.9 mg/g). The FC & the TC have strong α-glucosidase inhibitory activities with IC50 of 8.72 μg/mL and 3.67 μg/mL, respectively. We find that FC show competitive inhibition against α-glucosidase, while the TC exhibits noncompetitive inhibition. Furthermore, The FC exhibits significant radical scavenging activity with the EC50 values of 7.73 μg/mL, 3.64 μg/mL and 5.90 μg/mL on DPPH radical, hydroxyl radical and ABTS radical, respectively. The FC also shows moderate anti-lipid peroxidation activity with the IC50 values of 41.77 μg/mL on inhibiting β-carotene bleaching.ConclusionThese results imply that the FC and the TC could be responsible for the good clinical effects of APL on T2MD through targeting oxidative stress and postprandial hyperglycaemia. So APL may be good sources of natural antioxidants and α-glucosidase inhibitors exhibiting remarkable potential value for the therapy of T2DM.