ANTIOXIDANTS FROM ASPARAGUS SPEARS: PHENOLICS

Extracts from asparagus (Asparagus officinalis) and isolated compounds have revealed a wide range of biological activities. Although the mechanism of action of the crude extracts and purified fractions is not well established yet, the antioxidant properties of asparagus may at least partly explain its therapeutic properties, since free radical damage is implicated in the etiology of different human diseases. The results of the present study show that asparagus spears can be considered an excellent source of natural antioxidants, such as phenolic compounds. These have been investigated by HPLC-DAD. The chromatograms have revealed that different flavonoids and hydroxycinnamic acids are correlated with antioxidant activity of asparagus ethanolic extracts. Two different methods (antiradical activity and reducing power) have been used to evaluate the antioxidant activity of asparagus samples of different origin: white and green spears of cultivar 'Grande' from Alcalá del Río (Seville) and from Huétor-Tájar (Granada), and green spears from a native cultivar 'Trigueros' from Huétor-Tájar. The analysis of the phenolic profiles from the different asparagus samples revealed that the green spears contain higher amounts of flavonoids and hidroxycinnamic acids than the white ones, which was correlated with greater antioxidant capacity of green asparagus. Sample origin was an important factor, with spears from Huétor-Tájar having not only higher antioxidant capacity and phenolic content, but also a larger variety of flavonoid compounds. Significant differences were also found between spears of the same origin, suggesting that genetics are another factor to take into account. In spears of 'Trigueros', which is a mixture of tetraploid and octaploid asparagus, seven “new flavonoids” have been detected, while 'Grande' (diploid) contained mostly rutin.