Correlation between antioxidant activity and phenolics of Corydalis ochroleuca extracts obtained by different extraction techniques

Abstract

Corydalis ochroleuca Koch. (Papaveraceae) called white corydalis is herbaceous perennial plant, native to rocky woodland areas of south-eastern Europe. It is recognized by narrow, tubular, fragrant white-yellow flowers. Currently, use of this plant is mainly associated with decorative purposes, while there is lack of data for other possibilities of its application. In this research, rhizome and vegetative shoot of C. ochroleuca collected from canyon of the Derventa river (National park Tara) located in western Serbia, were used to determine antioxidant activity by ABTS∙+, DPPH∙, in vitro phosphomolybdenum total antioxidant (TAC), cupric reducing antioxidant capacity (CUPRAC) and ferric reducing power (FRP) assays. For this purpose, samples were washed, powdered and extracted with 80% methanol by solvent extraction (SE) and ultrasound-assisted extraction (UAE). The aim of this study was to evaluate antioxidant activity of C. ochroleuca extracts and to determine their correlation with previously spectrophotometrically determined phenolic classes (total phenolics (TPC), total flavonoids (TFC), total hydroxycinnamic acid derivatives (HCAs)). The results of antioxidat assays show that the rhizome extract obtained by UAE show the highest antioxidant activity by ABTS∙+ (58.66% ± 0.72) and CUPRAC (67.30 ± 0.73 mg/g AAE). In the case of DPPH∙, TAC and FRP assays, extracts of vegetative shoot obtained by both extraction techniques (SE and UAE) show higher antioxidant activity then rhizome extracts. Correlation analysis confirmed a positive correlation between TFC and antioxidant tests - DPPH∙ (r= 0.96; p˂ 0.1) and TAC (r= 0.92; p˂ 0.1), and between HCAs and DPPH∙ (r= 0.91; p˂ 0.1), respectively. DPPH∙ is a known lipophilic and stable free radical, so this result indicates that the extract of the tested plant was rich in lipophilic flavonoids and chlorogenic acid derivatives that are able to donate H+ ions and neutralize the DPPH radical. Conclusion. Also, there was good correlation between DPPH∙ and TAC (r= 0.99; p˂ 0.1). It is assumed that the total flavonoids, which show the same activity according to these assays, contributed to this correlation. In general, flavonoids apparently contribute to high antioxidant activity of C. ochroleuca which indicate a complex flavonoid profile. Further research should focus on detailed phenolic characterization and analysis with their in vivo and in vitro properties.