Extraction and Isolation of Polymethoxylated Flavonoids from Pomelo Peels and the Antioxidant Stability of Its Oils
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Abstract:
Polymethoxylated flavonoids (PMFs) were extracted from pomelo (Citrus maxima) peels and separated using ultrasound-assisted technology combined with macroporous adsorption resins and preparative liquid chromatography. The PMF components were then analyzed by liquid chromatography-mass spectrometry (LC-MS). The results showed that pomelo peels contained five types of PMFs: citrin, tangerine, 3,5,6,7,8,3ʹ,4ʹ-heptamethoxy flavonoid, 5-hydroxy-3,6,7,8,3ʹ,4ʹ-hexamethoxy flavonoid, 5-hydroxy-3,3ʹ,7, 8-tetramethoxy-4ʹ, and 5ʹ-methylenedioxy flavonoid, with their contents being 5.12%, 4.29%, 4.33%, 4.10%, and 3.07%, respectively. Furthermore, when the PMF concentration reached 2 mg/mL, DPPH and ABTS+ free radicals showed maximum scavenging rates of 75.90% and 78.85%, respectively. In the APPH-induced RBC hemolysis model, the hemolysis rate was significantly reduced from 80.20% to 48.89% with 0.05 mg/mL PMFs. In addition, the PMF extract of pomelo peels had an antioxidant effect on oils and fats in oil cake fried at 180 ℃ for 1~5 h. Compared with the blank group (peroxide value of 0.16~0.28 g/100 g, acid value of 0.36~1.42 mg/g, anisidine value of 4.49~7.08), the physical and chemical indices of the PMF extract from pomelo peels with 1% flour content showed little change (peroxide value (0.15~0.19 g/100 g) , acid value (0.34~1.25 mg/g), whereas the lipid anisidine value (AV) decreased significantly with 0.5% flour content of PMFs (anisidine value 0.91~5.5). In conclusion, the five types of PMFs in pomelo peels have an optimal scavenging effect on free radicals and exhibit resistance towards lipid oxidation.
