Orange peel is the dried, ripe peel of Citrus reticulata Blanco and its cultivars in the Rutaceae family. According to the different origins and varieties, tangerine peel medicinal materials are divided into "tangerine peel" and "guang tangerine peel". Cantonese tangerine peel refers to the tangerine peel mainly produced in Xinhui, Guangdong. It is processed from the ripe peel of Citrus reticulata 'Chachi', a cultivar of tangerine. It is the top grade of tangerine peel medicinal materials. Since ancient times, Cantonese tangerine peel is the first of the Three Treasures of Guangdong. In order to explore the mechanism of "Chen Jiu Zheliang" of Cantonese tangerine peel, Professor Wu Hong's team used ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS), combined with metabolomic analysis methods to analyze different aging methods. Years (0-4 and 29 years) of flavonoids in tangerine peels were studied (below).
Figure 1 Samples of Cantonese tangerine peel (0, 1, 2, 3, 4, 29 years)
The results showed that a total of 219 flavonoid metabolites (flavonoid metabolites) were detected, including 5,7,3',4',5'-pentamethoxydihydroflavonoids, 2'-hydroxy-3,4,5, 3'4',6'-hexamethoxychalcone was detected for the first time in tangerine peel. According to metabolite cluster analysis, 0, 1, and 2 years old dried tangerine peel belonged to one category, and 3, 4, and 29 years old dried tangerine peel belonged to another category. The quantitative analysis results showed that the content of 4 flavonoid glycosides in the former type of tangerine peel was higher than that of the latter type, and the content of 15 polymethoxyflavonoids was higher than that of the latter type. The unaged tangerine peel (0 years) was compared with the other five groups of tangerine peels (1, 2, 3, 4, and 29 years) with different aging years, and it was found that poplaraxanthin, apigenin, 2'- Hydroxyisoflavones, luteolin, 6-hydroxyluteolin, gallocatechin, quercetin-O-acetylhexoside and apigenin-7-O-[β-D-glucuronide (1→ 2)-O-β-D-glucuronide) These eight flavonoids can be used as the landmark components to distinguish the unaged new skin from the aged skin.
APC showed that the total antioxidant activity of tangerine peel in 3 and 4 years was stronger than that in other years. It shows that the composition of tangerine peel has changed in quality and quantity after being aged for more than three years, and the aging directly promotes the increase of the types and contents of polymethoxyflavonoids in tangerine peel. Polymethoxyflavones not only have good antioxidant activity, but also alleviate metabolic syndromes such as hypertriglyceridemia, fatty liver, and insulin resistance by regulating intestinal microbes and amino acid metabolism. Growth, induction of tumor cell apoptosis and other pathways play a role in the treatment of cancer.
However, through molecular docking of 8 important flavonoids in tangerine peel with the new coronavirus (SARS-CoV-2) Spike protein, SARS-CoV-2 RNA polymerase and important proteases (3CLpro, PLpro), it was found that there are some flavonoids in tangerine peel. The binding affinity of flavonoids to four important functional proteins of SARS-CoV-2 was significantly better than that of the positive control drug. The results showed that the content of potential components against 2019-nCoV in Canton tangerine peel new peel (0 years old) was significantly higher than that of aged old peel.
Based on this, the researchers suggest that when using tangerine peel with polymethoxyflavonoids as the active ingredient, it is recommended to use tangerine peel for more than 3 years. If it is developed and utilized as an antioxidant, it is best to age 3-4 years of dried tangerine peel. When used as an anti-coronavirus drug, it is better to use unaged new skins. The results of this study provide scientific data for the quality control, evaluation and rational utilization of different aged tangerine peel medicinal materials, and also provide basic data for in-depth analysis of the metabolic regulation of the medicinal components of tangerine peel.
