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Potential applications of gold nanoparticles in biomedicine have increasingly been reported on account of the ease of synthesis, bioinert characteristics, optical properties, chemical stability, high biocompatibility, and specificity. The safety of these particles remains a great concern, as there are differences among toxicity study protocols used. This article focuses on integrating results of research on the toxicological behavior of gold nanoparticles. This can be influenced by the physicochemical properties, including size, shape, surface charge, and other factors, such as methods used in the synthesis of gold nanoparticles, models used, dose, in vivo route of administration, and interference of gold nanoparticles with in vitro toxicity assay systems. Several researchers have reported toxicological studies with regard to gold nanoparticles, using various in vitro, in vivo, and in ovo models. The conflicting results concerning the toxicity of gold nanoparticles should thus be addressed to justify the safe use of gold nanoparticles in biomedicine.

a b s t r a c tAim: To validate plant species for hypoglycaemic activity. Materials and methods: Four plants were investigated for hypoglycaemic activity by evaluating inhibiting effects on carbohydrate-hydrolising enzymes: ␣-glucosidase and ␣-amylase. Acetone plant extracts were screened against C2C12 myocytes, 3T3-L1 preadipocytes and Chang liver cells by measuring glucose uptake. Cytotoxicity was done in preadipocytes and hepatocytes. Results: Extract of Euclea undulata rootbark exhibited highest activity, displaying a glucose uptake of 162.2% by Chang liver cells at 50 g/ml. An inhibition concentration of 50% for Euclea undulata was found to be 49.95 g/ml for ␣-glucosidase and 2.8 g/ml for ␣-amylase. No cytotoxicity was recorded for Euclea undulata, while Schkuhria pinnata and Elaeodendron transvaalense exhibited cytotoxicity at 12.5 g/ml. ␣-Glucosidase and ␣-amylase assays showed inhibitory activity on enzymes for three plant extracts. Conclusion: Euclea undulata, Schkuhria pinnata and Elaeodendron transvaalense showed in vitro hypoglycaemic activity. Schkuhria pinnata and Elaeodendron transvaalense indicated cytotoxicity on 3T3-L1 preadipocytes and Chang liver cells. Euclea undulata, Pteronia divaricata and Elaeodendron transvaalense inhibited ␣-glucosidase and ␣-amylase enzymes. Ethnopharmacological relevance: Screening of plant extracts scientifically validated traditional use of Euclea undulata for treatment of diabetes. Cytotoxicity results revealed that acetone extracts of Schkuhria pinnata and Elaeodendron transvaalense are toxic and raise concern for chronic use.