Influence of Environmental Factors on Green Asparagus Flavonoids

We have previously reported that there is high correlation between antioxidant capacity and total phenol content in green asparagus (RODRÍGUEZ et al. 2005), which suggests that phenols could be mainly responsible for that activity as happens for other plant-derived products (VINSON et al. 1998; KAMAT et al. 2000; NINDO et al. 2003; PELLEGRINI et al. 2003). It has also been established that flavonoids are the most abundant phenolics in green asparagus and that their profile is significantly different among genotypes (FUENTES-ALVENTOSA et al. 2007, 2008). The composition of flavonoids in plants is influenced by both genetic factors and environmental conditions. It has been previously reported that the former seem to be a determinant factor because significant differences were found between green (triguero) native spears and commercial hybrids of green asparagus both cultivated in the same area (FUENTES-ALVENTOSA et al. 2008). The main objective of the present work is to determine the influence of cultivation area and harvest date on the content and composition of flavonoid glycosides from several green asparagus genotypes. The variability of flavonoid composition among spears of the same genotype collected from different plants has also been investigated. Quantitative evaluation of flavonoid content was carried out by HPLC-DAD-MS, as described by FUENTES-ALVENTOSA et al. (2007). Flavonoid glycosides and flavonols were identified by using their retention times and both spectroscopic and mass spectrometric data. Quantification of individual flavonoids was directly performed by HPLC-DAD using an eight-point regression curve in the range of 0-250 μg on the basis of standards. Where standards were not available, quantification was based on an average value for that class of compound, since responses were essentially similar within classes. Results were calculated from the mean of three replicates. From the results of this study it can be concluded that flavonoid composition of green asparagus was influenced by both cultivation area and harvest date, whereas no significant differences were found among spears of the same genotype from different plants within an asparagus field.