Extraction and analysis of antioxidant compounds from the residues of Asparagus officinalis L

Abstract

Asparagus residues were used as materials to obtain antioxidant compounds by solid-liquid extraction in this study. The effects of different extraction parameters including extraction solvents, time, temperature and liquid-solid ratio on the contents of total flavonoids, total phenolics and total antioxidant activity were investigated. Antioxidant activity of the extract from asparagus residues was evaluated by HPLC- ABTS · (+) and the bioactive components were identified by HPLC- MS/MS. The results showed that the extraction yield was significantly influenced (P < 0.05) by solvent composition, extraction time and temperature. The appropriate parameters were preferred as extraction solvent of 50 % ethanol with liquid-solid ratio of 30:1, extraction temperature of 80 °C and time of 2 h. Antioxidant activity evaluation of the extract indicated flavonoids and phenolics were dominant bioactive compounds. Five antioxidant compounds were identified as ferulic acid, kaempferol, quercetin, rutin and isorhamnetin.

Keywords: Antioxidant activity; Asparagus residues; Extraction; Flavonoids; Phenolics.

Fig. 1

Comparison of experimental (symbols) and predicted by Peleg’s model (line) values for the extraction of antioxidant compounds from asparagus residues with 50 % aqueous ethanol (each experimental value was the mean of three measurements)

Fig. 2

Influence of extraction temperature on the contents of total phenolics, total flavonoids and total antioxidant activity (DPPH, ABTS assays) of the extracts from asparagus residues ^a. Theresults were expressed as mean ± standard deviation (n = 3), the different letters indicated that the difference was significant (P < 0.05), and the only same letter was expressed as insignificant difference (P > 0.05). ^a Extractions were carried out for 2 h with the solvent of 50 % ethanol

Fig. 3

Influence of liquid–solid ratio on the contents of total phenolics, total flavonoids and total antioxidant activity (DPPH, ABTS assays) of the extracts from asparagus residues^b. The results were expressed as mean ± standard deviation (n = 3), the different letters indicated that the difference was significant (P < 0.05), and the only same letter was expressed as insignificant difference (P > 0.05). ^b Extractions were carried out for 2 h with the solvent of 50 % ethanol at temperature of 80 °C

Fig. 4

HPLC-ABTS · ⁺ chromatographic profiles of antioxidant compounds in ethyl ether fraction of the extract^c. ^c Extraction was carried out at 80 °C for 2 h with 50 % ethanol in liquid–solid ratio of 30:1

Fig. 5

HPLC-ABTS · ⁺ chromatographic profiles of antioxidant compounds in ethyl acetate fraction of the extract

Fig. 6

HPLC-ABTS · ⁺ chromatographic profiles of antioxidant compounds in n-butanol fraction of the extract

Fig. 7

HPLC-ABTS · ⁺ chromatographic profiles of antioxidant compounds in aqueous fraction of the extract