Heat Stable Inhibitors of Protein Cross-linking from Sri Lankan Medicinal Plants

Aims: Glycation induced protein cross-linking is recognized as the most damaging element of advanced glycation end product formation and is a key player of diabetic complications. Objectives of the present study were to assess the heat stability of potential glycation inhibitors of seven medicinal plants and to investigate whether the cross-linking is inhibited when the extracts are added after the commencement of glycation.

Study Design: Experimental.

Place and Duration of Study: Department of Biochemistry, Faculty of Medicine, University of Peradeniya, Sri Lanka, from May 2013 to March 2014.

Methodology: Plant parts with promising in vitro cross-link inhibitory potential were analyzed. Lysozyme and fructose system was used as the glycation model. Effect of heated (at 95ºC for 1 hour) and non heated samples on fructosamine formation and glycation induced protein cross-linking was compared using nitroblue tetrazolium method and sodium dodecyl sulfate polyacrylamide gel electrophoresis respectively. Effect of the addition of non heated samples on day 0, 1 and 2 on cross-linking was also compared.

Results: Both heated and non heated extracts of Coriandrum sativum seed, Phyllanthus debilis whole plant, Phyllanthus emblica fruit, Syzygium aromaticum flower and Syzygium cumini leaf showed reduction in the formation of fructosamine and lysozyme cross-links almost to the same extent. There was a reduction in the inhibitory effects of the heated samples of Ficus racemosa stem bark and Pterocarpus marsupium latex. All seven samples prevented further increase in cross-linking when added on day 1 of the incubation, but not when added on day 2 except for S. cumini.

Conclusion: C. sativum, P. debilis, P. emblica, S. aromaticum and S. cumini extracts possess thermo stable compounds that inhibit fructosamine and glycation induced protein cross-linking. Plants used are likely to have inhibitory effects on early or middle stages of glycation and did not demonstrate the ability of breaking cross-links.