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Radiolytic synthesis provides a convenient and environmentally-friendly approach to prepare metallic nanoparticles in large scale with narrow size distribution. In this report, colloidal silver nanoparticles (AgNPs) were synthesized by gamma radiation using poly(vinyl alcohol) (PVA) or silk fibroin (SF) as stabilizers and were evaluated for their antibacterial properties. The conversion of metallic silver ions to silver atoms depended on irradiation dose and stabilizer concentration as determined by UV-Vis spectrophotometry and transmission electron microscopy. The uniformly dispersed AgNPs with diameter 32.3 ± 4.40 nm were evaluated as antiseptic agents in films composed of chitosan, SF, and PVA that were processed by irradiation-induced crosslinking. Using disc diffusion assay, the films containing 432 ppm AgNPs could effectively inhibit the growth of bothStaphylococcus aureusandPseudomonas aeruginosa. Therefore, we have demonstrated in our present study that gamma radiation technique can potentially be applied in the mass production of antibacterial wound dressings.

Carissa carandas, commonly known in Thai as 'nham-daeng', has a long history in alternative medicine in Thailand. Ethanolic extracts of fresh leaves, unripe fruits and fully-ripe fruits were investigated for their antioxidant activity, total phenolic content, total anthocyanins, anthocyanin identification, vitamin C content and cytotoxicity. Results showed that the leaf extract exhibited the highest antioxidant activity, FRAP value and total phenolic content. The antioxidant activities of leaf, unripe and fully-ripe fruit extracts were 65.24±0.69, 0.85±0.03 and 2.42±0.41 mg AAE/g, respectively. Total phenolic contents were 24.91±0.22, 1.29±0.16 and 4.67±0.41 mg GAE/g and total anthocyanins were 0, 0.33±0.04 and 54.80±6.07 mg/l, respectively. The fully-ripe fruit extract, which showed low antioxidant activity and total phenolic contents, exhibited the highest total anthocyanins and cyanidin-3-galactoside levels. The unripe fruit extract showed the highest content of vitamin C (300.75±57 mg/100g). The major anthocyanin of all samples was cyanidin-3-galactoside. At a concentration of 200 µg/ml, treatment with the leaf extract caused the greatest reduction in HepG2 viability among the three extracts. These results indicated that the amounts of total phenolics and antioxidant activity could be correlated with cytotoxicity on HepG2 cells for the leaf sample.

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