Herb and spice extracts inhibit protein glycation

Abstract

We hypothesized that substances in herbs and spices may inhibit protein glycation. Extracts of 20 herbs and spices were tested for ability to inhibit glycation of albumin. Dry samples were ground and extracted with 50% ethanol (10% w/v), and total phenolic content and ferric reducing antioxidant potential (FRAP) were measured. Aliquots were incubated in triplicate at 37°C in 0.2 M potassium phosphate buffer, pH.7.4, containing 0.25 M fructose and 10 mg/ml fatty acid-free bovine albumin with final concentrations of total phenolics from 33 to 267 μg/mL. After 4 days, fluorescence was measured at 440 nm as an index of the formation of glycated albumin. In general, the spice extracts inhibited glycation more than the herb extracts. When tested at 267μg/mL total phenolics, the most potent inhibitors included clove (83.5%), ground Jamaican allspice (67.8%), and cinnamon (65.0%). Potent herbs tested included sage (49.1%), tarragon (48.1% ), and rosemary (47.7%). Inhibition of glycation by spice extracts was concentration dependent and correlated with total phenolic and FRAP values (R²=0.66 and R²=0.51, respectively) whereas the inhibition by herb extracts was not highly correlated (R²=0.14 and R²=0.004, respectively). Total phenolics were highly correlated with FRAP (R²=0.93). The evidence shows that compounds found in herb and spice extracts inhibit albumin glycation in vitro. Not all active substances appear to be polyphenolics. (Supported by AES Hatch project GE09622)