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A comparative study was carried out on the methanolic extracts from six Achillea species and the examined polyphenols from these plants on the formation of advanced glycation end-products (AGE) in vitro. A. pachycephala which was richer in flavonoids (15 mg quercetin/g W) and phenolics (111.10 mg tannic acid/g DW) with substantial antioxidant activity (IC = 365.5 μg/ml) presented strong anti-AGE properties. Chlorogenic acid, luteolin, quercetin and caffeic acid were identified as the major polyphenols in the extracts by HPLC. In general, polyphenolic content follows the order of A. pachycephalla > A. nobilis > A. filipendulina > A. santolina > A. aucheri > A. millefolium. Most extracts exhibited marked anti-AGE ability in the bovine serum albumin (BSA)/methylglyoxal (MG) system, though A. pachycephala showed the highest potential. The formation of AGEs was assessed by monitoring the production of fluorescent products and circular dichroism (CD) spectroscopy. Diminution in free radical production (assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays) is discussed as potential mechanism for delay or reduced AGE. The results demonstrate the antiglycative, antioxidant and antimicrobial potential of Achillea species which can be attributed to polyphenols content and the effectiveness on generation of AGEs, thus Achillea species can be considered as natural sources for slowing down glycation related diseases.

Both physical and chemical procedures were applied to immobilize yeast alcohol dehydrogenase (yADH) on titania nanoparticles. It was found that chemical immobilization is an authentic method due to providing a strong bond between the enzyme and the support. The immobilization was confirmed by Fourier transform infrared spectroscopy and transmission electron microscopy. The immobilization parameters such as enzyme concentration, time of immobilization, and glutaraldehyde concentration were optimized based on the maximum immobilization yield and the best enzyme catalytic performance. Activity and kinetics of yADH before and after immobilization were studied, and the stability of enzyme at different pHs and temperatures was investigated. The optimum pH for the incubation and activity of yADH was obtained at 7.0, and the activity of immobilized yADH reached more than 80% of its initial activity after 30 days of storage at 4 °C. The reusability of yADH was improved by immobilization as revealed by retaining 84% of its initial activity following 10 cycles. Finally, we suggested that the immobilization of yADH is a promising method for the removal of substrate inhibition in the reaction of formaldehyde to methanol.

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