Evaluation of antioxidant-associated efficacy of flavonoid extracts from a traditional Chinese medicine Hua Ju Hong (peels of Citrus grandis (L.) Osbeck)

Ethnopharmacological relevance: Hua Ju Hong (HJH, peels of Citrus grandis (L.) Osbeck) is a popularly used traditional Chinese medicine recorded by "Compendium of Materia Medica" (Ben Cao Gang Mu) in Ming Dynasty of China (1578 A.D.). With flavonoid components, HJH possesses hypolipidemic effect associated with antioxidation action. However, no report was found regarding the flavonoid profile and antioxidant activity of HJH.

Materials and methods: Five purified flavonoid extracts (TFCA, TFCB, TFCC, TFCD and TFCE.) were obtained from HJH using Ca(OH)2 and HPD-300 macroporous resins, and their total flavonoids and representative flavonoid components were analyzed. In vitro tests of DPPH free radical scavenging activity, reducing power, and total antioxidant activity of each extract were evaluated. The most effective extract was selected for in vivo antioxidative evaluation using a rat hyperlipemia model.

Results: The total flavonoid content was varying among each HJH extract and decreased in an order of TFCB>TFCD>TFCC>TFCE>TFCA. TFCB, TFCD, and TFCC contained more than 50% of total flavonoids, the highest content of which was found in TFCB (80.7%). HPLC analysis showed that the contents of three flavonoid components, narirutin, naringin and neohesperidin, displayed a similar trend as that of total flavonoids. In vitro antioxidative tests determined that TFCB at 0.24 to 1.2mg/ml possessed the most significant antioxidant effects among other extracts and was also superior to BHT. In vivo experiment also revealed the significant antioxidant and antihyperlipidemic activities of TFCB started from 50 to 200mg/kg after oral administration to hyperlipemia rats. These results indicate that TFCB with the highest flavonoid contents has the strongest antioxidant-associated activities.

Conclusion: This is the first report regarding antioxidant-associated activities and relevant flavonoid components of HJH extracts, providing a promising candidate of traditional Chinese medicine for antioxidative treatment.