High-Performance Liquid Chromatography Characterization and Identification of Antioxidant Polyphenols in Maple Syrup

Abstract

Maple syrup of four grades (extra-light, light, medium, and dark) of the 2007 crop was provided by three local (St. Joseph's Island, Ontario, Canada) producers. Twenty-four phenolic compounds were isolated from a medium-grade syrup and identified on the basis of spectral and chemical evidence. They were (a) benzoic acid and several hydroxylated and methoxylated derivatives (gallic acid, 1-O.-galloyl-β-d-glucose, γ-resorcylic acid); (b) cinnamic acid derivatives (p.-coumaric acid, 4-methoxycinnamic acid, caffeic acid, ferulic acid, sinapic acid, and the ester chlorogenic acid); (c) flavonoids, the flavanols catechin and epicatechin, and the flavonols kaempferol and its 3-O.-β-d-glucoside, 3-O.-β-d-galactoside, quercetin and its 3-O.-β-d-glucoside, 3-O.-β-L-rhamnoside and 3-O.-rhamnoglucoside (rutin). Traces obtained at 280 and 350 nm in HPLC runs of the ethyl acetate–soluble fractions of eight samples indicated the presence of many more phenolic substances, most at very low concentration with some varibilities in peak heights, but not in retention times, among the syrups. In view of the well-established antioxidant activity these substances possess, it is suggested that it is the complexity of the mixture rather than any one compound that may serve to counter the unhealthful presence of the high concentration of sugars in the syrup.     

On the photodegradation of azithromycin,erythromycin and tylosin and their transformation products – A kinetic study

In this study, the photo-induced degradation of azithromycin (Azi), erythromycin (Ery) and tylosin (Tyl) was investigated. The three macrolides are regularly found in different kinds of water, and are thus considered a potential environmental risk. In search of efficient ways for elimination, the compounds were systematically irradiated with a polychromatic UVC light source emitting 185, 254 and discretely further up to 580 nm. Due to their specific structural features, the macrolides possess different optical absorption characteristics leading to photodegradation pathways with dissimilar kinetic properties. Hence, the photodegradation products and their kinetics were analyzed using high-performance liquid chromatography (HPLC) coupled to high-resolution time-of-flight mass spectrometry. Among the degradants, i.e. the products formed during UV irradiation, both sugar moieties and lactone macrocycles were observed. Applying a first order kinetic model, the half-life of Azi was determined as 1.0?3.7 min, that of Ery as 1.0?14.2 min depending on the reaction conditions. The two compounds possess much lower absorption cross-sections than Tyl, in particular at 254 nm. Their half-lives appeared at least three times higher than that of Tyl that has t_1/2 of 0.2?1.0 min. Based on quantum efficiency considerations, it was assumed that the degradation of Ery and Azi was mainly due to hydroxyl radical formation, which originated from water irradiation below 200 nm, whereas Tyl experienced predominantly photo induced degradation. The photodegradants of Azi exhibited half-lives of over 200 min, whereas most of the photo-products of Ery and Tyl showed half-lives of less than 10 min. Photodegradation processes were investigated at pH 3, pH 7 and pH 9 and in the presence of hydrogen peroxide. Both the educts and the photo-products were degraded more rapidly under neutral and acid conditions.     

The Rewards and Challenges of Becoming a Clinical Instructor

Frontline nurses working in the clinical area are a vital component to nursing education. Taking on the role of adjunct clinical instructor can be a rewarding way to increase one's own knowledge while performing the important task of educating the next generation of nurses.     

Perceived Family and Friend Support and the Psychological Well-Being of American and Chinese Elderly Persons

This study examines two sources of informal support??perceived family and friend support??and the psychological well-being??self-esteem, depression and loneliness??of 150 Chinese and 145 American elders. There were no significant differences between the elderly American and Chinese persons?? mean scores on family and friend support. The multiple linear regression analyses with interaction terms (country x family support and country x friend support), however, indicated that the relationship between family support and depression and family support and loneliness was stronger for the Chinese elderly than the US elderly. Conversely, the relationship between friend support and depression and friend support and loneliness is stronger for US elderly than Chinese elderly. The implications of these findings for social work practice in both countries is discussed.