Phenolic compounds and antioxidant activity in sweet potato after heat treatment

Abstract

BACKGROUND The ability of heat treatment with a soaking solvent to increase soluble phenolic compounds due to the liberation or breakdown of the cell matrix has been investigated in various plants. This study investigated the changes in phenolic compounds and antioxidant activities of 12 sweet potato cultivars after heat treatment with distilled water or prethanol A. RESULTS The highest total polyphenol content (134.67 mg gallic acid equivalents/g extract residue) and flavonoid content (65.43 mg catechin equivalents/g extract residue) was observed in the ‘Jami’ (JM) cultivar after heat treatment with prethanol A. Higher polyphenol and flavonoid content was generally observed in the purple sweet potato cultivars. Salicylic acid was the major phenolic acid, followed by protocatechuic acid or chlorogenic acid in almost all untreated sweet potato cultivars. The salicylic acid, vanillic acid, gallic acid, and caffeic acid content of the sweet potatoes increased after the heat treatment, whereas the protocatechuic acid and chlorogenic acid content decreased. The highest 1,1‐Diphenyl‐2‐picrylhydrazyl (DPPH) and 2,2‐azinobis(3‐ethyl benzothiazoline)‐6‐sulfonic acid (ABTS) radical scavenging activity levels were observed in the JM cultivar subjected to heat treatment with prethanol A (48.15 and 80.00 mg TE/g extract residue, respectively). CONCLUSION These results suggest that heat treatment with a soaking solvent is an efficient method to enhance the antioxidant characteristics of Korean sweet potato cultivars. © 2019 Society of Chemical Industry

Influence of Heat Treatments on the Content of Bioactive Substances and Antioxidant Properties of Sweet Potato (Ipomoea batatas L.) Tubers

“…. Phenolic compounds are the primary antioxidants found in fruits, vegetables, and grains [28]. Sweet potatoes, which are also a source of many other bioactive substances, are also characterized by a high content of polyphenolic compounds [33].…”

“…ese acids are the main component of sweet potato phenolic compounds. Chlorogenic acid and isochlorogenic acid are the primary acids [17,26,28]. Precision or repeatability of retention times and peak areas from five standards was calculated using percent relative standard deviation (% RSD) and is presented in Table 5.…”

“…Its content (mg/g DW) decreased as a result of heat treatment in the order: raw (0.46) > microwaved (0.34) > baked (0.26) > boiled (0.20). e authors of [28] evaluated the effect of heat treatment with distilled water and methanol A on several phenolic acids, e.g., vanillic acid, protocatechuic acid, gallic acid, chlorogenic acid, and caffeic acid. After heat treatment with distilled water, as protocatechuic acid and chlorogenic acid content decreased, on the contrary, the content of minor phenolic acids of SP-vanillic acid, gallic acid, and caffeic acid-increased.…”

“…Chlorogenic acids in plants have high antioxidant activities, such as reducing power, metal chelating, and lipid peroxidation-inhibiting activity [27]. us, in addition to antimutagenic and anticarcinogenic effects in vitro and in vivo, chlorogenic acid can prevent the formation of hydroxyl radicals, remove free radicals, and eliminate oxidative activity [28]. However, there are only a few studies about the differences in antioxidant activities between different chlorogenic acids, which does not provide sufficient theoretical support for the application of antioxidant activities [27].…”

Grown to be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables

“…Starch is the main calorific component of sweet-potato tubers with significant variation in its structural and functional properties which depend mostly on the genotype and are not correlated with flesh color [118], although, using a proteomic approach, a recent study revealed that starch degradation may contribute to anthocyanin biosynthesis and accumulation in purple sweet-potato roots [119]. Chlorogenic acid, protocatechuic acid, salicylic acid, and caffeoylquinic acid derivatives are the main phenolic acids detected in purple sweet-potato roots and are responsible for their antioxidant capacity [48,120,121], while orange-fleshed sweet-potato cultivars are rich in provitamin A and also show significant antioxidant activity [113,122,123]. Moreover, in the study of Lebot et al [124], the antioxidant activity of sweet-potato cultivars with purple, orange, and white flesh was correlated mostly with the presence of caffeoylquinic acid derivatives and less with total anthocyanin content, whereas, according to Oki et al [8], the contribution of phenolic compounds in radical-scavenging activity is also dependent on the genotype.…”