Potential of Gynura procumbens leaves as source of flavonoid-enriched fractions with enhanced antioxidant capacity

• Key active compounds from Gynura procumbens were purified using multiple steps.
• All of various fractions, sub-fraction 3 showed highest antioxidant activity.
• Major phenolic acids were isolated and identified as ferulic acid and sinapic acid.
• No correlation between total phenolic content and antioxidant activity.
• Myricetin and kaempferol were major flavonoid contributors to antioxidant activity.

Gynura procumbens has been consumed for a longtime in tropical regions as a vegetable with health promoting activities. We investigated phenolic antioxidants that were fractionated from the crude extract of G. procumbens leaves by Sephadex LH-20 column chromatography. Sub-fraction 3 had the highest antioxidant activity as well as its total phenolic and flavonoid contents. The IC50 values of sub-fraction 3 were 19 and 12 µg/ml, which were lower than those of ascorbic acid and trolox for DPPH
• and ABTS
• + assays, respectively. The major phenolic acids identified in sub-fraction 3 were ferulic acid and sinapic acid, whereas predominant flavonoids were myricetin and kaempferol. There was a strong positive correlation between antioxidant activity and total flavonoid content; however, no correlation existed between those and total phenolic content. Our findings suggest that the strongest antioxidant activity in sub-fraction 3 came from the flavonoids, especially myricetin and kaempferol, rather than phenolic acids.