Detection of Bioactive Compounds in Organically and Conventionally Grown Asparagus Spears

In the recent reports, there are contradictory conclusions about the nutritional and health properties of organic and conventionally growing vegetables. We hypothesized that organic cultivation system results in higher quality of asparagus (Asparagus officinalis L.) because of organic manure and effective organisms. Therefore, new analytical methods were applied in order to find the differences in bioactive compounds between the plants growing under various cultivation systems. Total antioxidant capacities (TAC) of the conventional and organic greenhouse and conventional open-field farming of asparagus spears were determined by 2,2-azino-bis (3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt (ABTS), 1,1-diphenyl-2-picryl-hydrazyl (DPPH), and ferric-reducing antioxidant power (FRAP) assays, and UHPLC-PDA-MS was used for identification of some phenolic acids and flavonoids. Total phenolic compounds (TPC), total flavonoids, rutin, vitamin C, chlorophylls, carotenoids, and the values of TAC, determined in organic growing asparagus spears, were higher than in conventional, but not always significant. The applied for the first time FTIR spectroscopy as an estimation of the differences between the investigated samples showed more prominent bands in the region of polyphenols in organic asparagus spears than in conventional and provides a rapid and precise alternative to other methods. The binding properties of extracted polyphenols to HSA determined by 3D-fluorescence were relatively higher in organic asparagus spears than in other samples. Correlation between the amounts of total polyphenols and flavonoids and their quenching properties showed a linear relationship. All proposed analytical methods can be applied to a variety of studied plants.