Browsing by Author "Hsu, Jue-Liang"
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ItemEffect of drying process on the production of 5-hydroxymethylfurfural in citrofortunella microcarpa at two different maturity stagesCitrofortunella microcarpa is a well-known citrus fruit as a good source for flavonoids and antioxidant compounds in peels and seeds. However, they are leftover from juice industry. 5-Hydroxymethylfurfural (HMF) is well-recognized for its dominant role in immunology field, and commonly found in thermal-processed products. Thus, this study aimed to first time report HMF discovery from dried C. microcarpa waste. A conventional hot air drying method was used to determine the effects of drying temperatures (30 - 70 °C) and times as well as the maturity stages of C. microcarpa on HMF production. Liquid chromatography-tandem mass spectrometry (LC-MS") and nuclear magnetic resonance (NMR) were used to characterize the produced HMF. The results showed that HMF production was positively correlated with drying temperature and drying time. Furthermore, the mature fruits produced significantly higher HMF levels than immature fruits. The highest amount of HMF (0.86 mg/g dry weight) was obtained from drying mature fruit at 70°C for four days.
ItemGallic acid content in taiwanese teas at different degrees of fermentation and its antioxidant activity by inhibiting PKCδ activation: in vitro and in silico studiesTeas can be classified according to their degree of fermentation, which has been reported to affect both the bioactive components in the teas and their antioxidative activity. In this study, four kinds of commercial Taiwanese tea at different degrees of fermentation, which include green (non-fermented), oolong (semi-fermented), black (fully fermented), and Pu-erh (post-fermented) tea, were profiled for catechin levels by using high performance liquid chromatography (HPLC). The result indicated that the gallic acid content in tea was directly proportional to the degree of fermentation in which the lowest and highest gallic acid content were 1.67 and 21.98 mg/g from green and Pu-erh tea, respectively. The antioxidative mechanism of the gallic acid was further determined by in vitro and in silico analyses. In vitro assays included the use of phorbol ester-induced macrophage RAW264.7 cell model for determining the inhibition of reactive oxygen species (ROS) production, and PKCδ and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit (p47) activations. The results showed that only at a concentration of 5.00 μM could gallic acid significantly (p < 0.05) reduce ROS levels in phorbol ester-activated macrophages. Moreover, protein immunoblotting expressed similar results in which activations of PKCδ and p47 were only significantly (p < 0.05) attenuated by 5.00 μM treatment. Lastly, in silico experiments further revealed that gallic acid could block PKCδ activation by occupying the phorbol ester binding sites of the protein.
ItemNumber of hydroxyl groups on the B-ring of flavonoids affects their antioxidant activity and interaction with phorbol ester binding site of PKCδ C1B domain: in Vitro and in silico studiesAlthough ﬂavonoids have been reported for their beneﬁts and nutraceutical potential use, the importance of their structure on their beneﬁcial eﬀects, especially on signal transduction mechanisms, has not been well clariﬁed. In this study, three ﬂavonoids, pinocembrin, naringenin, and eriodictyol, were chosen to determine the eﬀect of hydroxyl groups on the B-ring of ﬂavonoid structure on their antioxidant activity. In vitro assays, including DPPH scavenging activity, ROS quantiﬁcation by ﬂow cytometer, and proteins immunoblotting, and in silico analysis by molecular docking between the ﬂavonoids and C1B domain of PKCδ phorbol ester binding site were both used to complete this study. Eriodictyol (10 μM), containing two hydroxyl groups on the B-ring, exhibited signiﬁcantly higher (p < 0.05) antioxidant activity than pinocembrin and naringenin. The IC50 values of eriodictyol, naringenin, and pinocembrin were 17.4 ± 0.40, 30.2 ± 0.61, and 44.9 ± 0.57 μM, respectively. In addition, eriodictyol at 10 μM remarkably inhibited the phosphorylation of PKCδ at 63.4% compared with PMA-activated RAW264.7, whereas pinocembrin and naringenin performed inhibition activity at 76.8 and 72.6%, respectively. According to the molecular docking analysis, pinocembrin, naringenin, and eriodictyol showed -CDOCKER_energy values of 15.22, 16.95, and 21.49, respectively, reﬂecting that eriodictyol could bind with the binding site better than the other two ﬂavonoids. Interestingly, eriodictyol had a remarkably diﬀerent pose to bind with the kinase as a result of the two hydroxyl groups on its B-ring, which consequently contributed to greater antioxidant activity over pinocembrin and naringenin.