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Summary Phenolic compounds, commonly found in plant‐based foods, exist in free or bound form. Despite much research on the soluble phenolics in spices and herbs, their bound phenolics have not been intensively investigated. In this study, six common dietary spices and medicinal herbs (Padang cassia, oregano, clove, Chinese cassia, Japanese knotweed and peel of pomegranate) were selected to evaluate and compare their phenolic composition and antioxidant capacity in soluble extracts (SEs) and bound extracts (BEs). Generally, the samples had high total phenolic content and antioxidant capacity, with lower levels in the BEs. From the HPLC results, (+)‐catechin, (−)‐epicatechin, eugenol, cinnamaldehyde and carvacrol were the major phenolic compounds in the SEs, and gallic acid, p‐coumaric acid and ellagic acid in the BEs. Phenolic compounds are likely the major contributors to the antioxidant capacity of these plant samples. Overall, these dietary spices and medicinal herbs can be excellent sources of natural antioxidant phenolics.

Hot air drying has been widely used for the processing and preservation of fresh fruits and vegetables. In this study, we investigated the browning of hot air dried mung bean (Vigna radiata L.) sprouts, as well as the antioxidant capacity and phenolic contents in their soluble and insoluble fractions. Hot air drying at 70 and 80C for 24 h increased the browning of mung bean sprouts, and hot air dried samples generally had higher total phenolic content and antioxidant capacity compared to the freeze‐dried sample. Rutin, caffeic acid and p‐coumaric acid were identified in mung bean sprouts by LC–MS, and hot air drying at higher temperature (70 and 80C) reduced rutin and p‐coumaric acid contents, while increasing the content of caffeic acid. Browning pigments and polyphenols may be the main contributors of antioxidant capacity in hot air dried mung bean sprouts. Practical Applications The mung bean sprout is a popular fresh vegetable in many Asian countries. We previously found that it had the highest antioxidant polyphenols among twelve cultivated edible bean sprouts, and this study further demonstrated that hot air drying was able to increase its antioxidant capacity and total phenolic conent compared to freeze‐dried samples. Therefore, hot air dried mung bean sprout powders are good natural source of antioxidant polyphenols, and can be used as additives to fortify food antioxidant polyphenols or developed into novel functional foods with potential health benefits. This finding should be of interest to the public and experts in the field of food science and technology.

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The red sword bean (Canavalia gladiata) is an underutilized edible bean cultivated in China. It was previously found to have the highest content of antioxidant polyphenols among 42 edible beans, mainly gallic acid, and gallotannins in its red bean coat, an apparently unique characteristic among edible beans. In this study, the main phenolic compounds in red sword bean coats were further separated by Sephadex LH-20 column chromatography, and identified by LC-MS/MS. Furthermore, the FRAP and ABTS antioxidant activities and antibacterial activity (diameter of inhibition zone, DIZ) of main gallotannin-rich fractions were tested. Our results showed that gallotannins of red sword bean coats were mainly comprised of monogalloyl to hexagalloyl hexosides. Interestingly, tetragalloyl, pentagalloyl, and hexagalloyl hexosides were identified as the possible candidates responsible for the red color of the coats. On the other hand, gallotannin-rich fractions exhibited diverse antioxidant and antibacterial activities, and tetragalloyl hexoside overall had the highest free radical scavenging and antibacterial activities. The degree of galloylation did not completely explain the structure-function relationship of gallotannins isolated from red sword bean coats, as there should exist other factors affecting their bioactivities. In conclusion, red sword bean coats are excellent natural sources of gallotannins, and their gallotannin-rich extracts can be utilized as natural antioxidant and antibacterial agents with potential health benefits as well as application in food industry.