Substituent Effects on in Vitro Antioxidizing Properties, Stability, and Solubility in Flavonoids

Abstract

Antioxidants are widely used by humans, both as dietary supplements and as additives to different types of products. The desired properties of an antioxidant often include a balance between the antioxidizing capacity, stability, and solubility. This review focuses on flavonoids, which are naturally occurring antioxidants, and different common substituent groups on flavonoids and how these affect the properties of the molecules in vitro. Hydroxyl groups on flavonoids are both important for the antioxidizing capacity and key points for further modification resulting in O-methylation, -glycosylation, -sulfation, or -acylation. The effects of O-glycosylation and acylation are discussed as these types of substitutions have been most explored in vitro concerning antioxidizing properties as well as stability and solubility. Possibilities to control the properties by enzymatic acylation and glycosylation are also reviewed, showing that depending on the choice of enzyme and substrate, regioselective results can be obtained, introducing possibilities for more targeted production of antioxidants with predesigned properties.

Storage Stability of Dietary Nitrate and Phenolic Compounds in Beetroot (Beta vulgaris) and Arugula (Eruca sativa) Juices

“…A principal sign of the degradation of betalains and betacyanins is a loss of color due to their pigment properties (Stintzing & Carle, ). The stability of flavonoids in different plant matrices has also been researched extensively (Plaza et al., ). It has been observed that a 1‐month storage of apple juice at refrigerator and room temperatures did not lower the concentration of total quercetin glycosides, total catechins, chlorogenic acid, phloridzin, and cyanidin galactoside (van der Sluis, Dekker, & van Boekel MAJS, ).…”

Enzyme‐ and ultrasound‐assisted extractions of polyphenols from Citrus sinensis (cv. Malta) peel: A comparative study

“…Results of the study showed highest AOX activity of EAE extract (Table ) which is in correlation with the results of the TPC and HPLC, depicting a direct relation of TPC and AOX activities (Anagnostopoulou, Kefalas, Papageorgiou, Assimopoulou, & Boskou, ; Cho et al, ). Furthermore, previous studies of Rice‐Evans et al (); Di‐Majo et al () and Plaza et al () suggested the mechanism of decrease in AOX activity with glycosylation under the ultrasonic and enzymatic processing conditions. Similar effect of ultrasonication on the AOX activities have been shown in the studies on grapefruit solid waste and C. limon, where the activity increased after the ultrasonic extraction (Dahmoune et al, ; Garcia‐Castello et al, ).…”

“…Similar results have been reported by Londoño‐Londoño et al (), Chamorro, Viveros, Alvarez, Vega, and Brenes (), and Nayak et al (), on citrus peels (sweet orange, lime, orange, and tangerine) and grape pomace, respectively. The variation in polyphenolic profile is attributed to the significant effect of processing conditions on conversion of galloylated form of polyphenolic compounds to agalloylated form with higher reducing activities (Cheynier & Halbwirth, ; Heim, Tagliaferro, & Bobilya, ; Plaza et al, ; Rice‐Evans, Miller, & Paganga, ; Williamson, Plumb, & Garcia‐Conesa, ).…”

Phytochemical profile of Paulownia tomentosa (Thunb). Steud.

“…For example, the antiradical activity is increased by 2 0 -hydroxyl substitution of the ring B, whereas 4 0 -methoxyl substitution diminishes it. The general rules postulated for the antioxidant activity of flavonoids in vitro are applicable (Havsteen 2002;Chen et al 2002), there are many review publications that touch on this topic, and it is not aim of this paper to delve deeply into this (Plaza et al 2014). The type of antioxidant assays used for the experiment could also be a factor that significantly affects this activity (Zima et al 2010).…”