Elastase/Collagenase Inhibition Compositions of <i>Citrus unshiu</i> and Its Association with Phenolic Content and Anti-Oxidant Activity

• Main Authors: Chang-Ho Eun, Mi-Sook Kang, In-Jung Kim
• Format: Article
• Language: English
• Published: MDPI AG 2020-07-01
• Series: Applied Sciences
• Subjects: citrus; anti-aging; GC-MS; heptadecanoic acid; D-allose; HMF
• Online Access: https://www.mdpi.com/2076-3417/10/14/4838

Citrus fruits are rich sources of different phytochemicals for human health due to their high anti-oxidant capacity. However, the anti-aging effect of citrus fruits has not been well understood. In this study, methanol extracts taken at various developmental stages from tissues of <i>Citrus unshiu</i> was used to investigate its anti-aging effect by an elastase/collagenase inhibition assay, and a gas chromatography-mass spectrometry (GC-MS) analysis was carried out to identify the potential anti-aging compositions. The elastase/collagenase inhibitory activity was greatest in the flesh of immature green fruit (i.e., early July flesh (EJF)), and four candidate compounds were selected by GC-MS and evaluated by a collagenase inhibition assay. Three of the four candidate compounds (heptadecanoic acid, D-allose, and 5-hydroxymethyl-2-furaldehyde (HMF)) showed anti-aging activity, and the activity was highest in heptadecanoic acid, followed by D-allose and HMF. The total phenolic content (TPC), total flavonoid content (TFC), and anti-oxidant activity (DPPH and ferric reducing anti-oxidant power (FRAP) assay) were also investigated. Interestingly, the patterns of the total phenolic/flavonoid content and the anti-oxidant activity were different from that of the elastase/collagenase inhibitory activity. Flowers had the most anti-oxidant activity followed by immature fruit, and the fruit peels had more anti-oxidant activity than its flesh at all stages of development. This study demonstrated that the flesh of immature fruit and flowers of <i>C. unshiu</i> could be sources of anti-aging and anti-oxidant agents for human health, respectively.