Efficient thermal treatment of radish (Raphanus sativus) for enhancing its bioactive compounds.

Old preserved radish (OPR), a traditional pickled-food of Asia, contains the healthy bioactive compounds, such as phenols and flavonoids. To preserve the phenols levels in radish by thermal treatment, which are decreased due to the polyphenol oxidase activity during long storage. Range of thermal processing evaluated to retain the maximum phenols level in the radish while processed at temperatures of 70 °C, 80 °C and 90 °C for 30 days. In this study, the bioactive compounds and antioxidant activity of thermal processing radish (TPR) were evaluated and compared with commercial products of OPR. Results showed the best condition of thermal processing, 80°C for 30 days, could increase the values of phenols, flavonoids and antioxidant activity that were 2.27, 2.74 and 2.89 times, respectively. When comparing the thermally processed radish or TPR with OPR, TPR has a higher content of phenols and flavonoids, indicating that the thermal processing was effective to increase the content of functional compounds in radish and significantly improved its nutritional values.

Reduction of 3-Deoxyglucosone by Epigallocatechin Gallate Results Partially from an Addition Reaction: The Possible Mechanism of Decreased 5-Hydroxymethylfurfural in Epigallocatechin Gallate-Treated Black Garlic.

5-Hydroxymethylfurfural (5-HMF) is a harmful substance generated during the processing of black garlic. Our previous research demonstrated that impregnation of black garlic with epigallocatechin gallate (EGCG) could reduce the formation of 5-HMF. However, there is still a lack of relevant research on the mechanism and structural identification of EGCG inhibiting the production of 5-HMF. In this study, an intermediate product of 5-HMF, 3-deoxyglucosone (3-DG), was found to be decreased in black garlic during the aging process, and impregnation with EGCG for 24 h further reduced the formation of 3-DG by approximately 60% in black garlic compared with that in the untreated control. The aging-mimicking reaction system of 3-DG + EGCG was employed to determine whether the reduction of 3-DG was the underlying mechanism of decreased 5-HMF formation in EGCG-treated black garlic. The results showed that EGCG accelerated the decrease of 3-DG and further attenuated 5-HMF formation, which may be caused by an additional reaction with 3-DG, as evidenced by LC-MS/MS analysis. In conclusion, this study provides new insights regarding the role of EGCG in blocking 5-HMF formation.

A strategy for promoting γ-glutamyltransferase activity and enzymatic synthesis of S-allyl-(L)-cysteine in aged garlic via high hydrostatic pressure pretreatments.

S-allyl-(L)-cysteine (SAC) is a bioactive compound within garlic. Its level is low since SAC formation is impeded by the cellular structure of garlic. This study investigates the effect of high hydrostatic pressure (HHP) pretreatment on SAC formation in garlic aged at 40 °C for 10 days. Results showed that HHP could enhance γ-glutamyltransferase (γ-GTP) activity, damage the cellular structure of garlic and increase SAC content in aged garlic by about 7-10 times, depending on the processing parameters. HHP processing at 300 MPa for 15 min provided the optimal conditions for enhancing γ-GTP activity (45%) and promoting SAC formation (from 0.51 ± 0.01 to 5.60 ± 0.22 mg/g dry weight). It was also found that HHP could induce the greening and browning of aged garlic. As such, we consider that HHP technology is a promising technique to produce aged black garlic products with higher amounts of bioactive compounds.

Extracts from Fermented Black Garlic Exhibit a Hepatoprotective Effect on Acute Hepatic Injury.

The mechanism of hepatoprotective compounds is usually related to its antioxidant or anti-inflammatory effects. Black garlic is produced from garlic by heat treatment and its anti-inflammatory activity has been previously reported. Therefore, the aim of this study was to investigate the hepatoprotective effect of five different extracts of black garlic against carbon tetrachloride (CCl4)-induced acute hepatic injury (AHI). In this study, mice in the control, CCl4, silymarin, and black garlic groups were orally administered distilled water, silymarin, and different fraction extracts of black garlic, respectively, after CCl4 was injected intraperitoneally to induce AHI. The results revealed that the n-butanol layer extract (BA) and water layer extract (WS) demonstrated a hepatoprotective effect by reducing the levels of alanine aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and hepatic malondialdehyde (MDA). Furthermore, the BA and WS fractions of black garlic extract increased the activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione reductase (GSH-Rd), tumor necrosis factor alpha (TNF-α), and the interleukin-1 (IL-1ß) level in liver. It was concluded that black garlic exhibited significant protective effects on CCl4-induced acute hepatic injury.