Comparison of the contents of bioactive compounds and the level of antioxidant activity in different kiwifruit cultivars

The aim of this investigation was to find the best among four different cultivars of kiwifruit ('Hayward', 'Daeheung', 'Haenam' and 'Bidan') for human consumption. The bioactive compounds and the level of antioxidant activity of these cultivars were determined and compared. The presence of polyphenols (flavonoids and phenolic acids) in the investigated samples was studied by Fourier transform infrared (FT-IR) spectroscopy. By far the highest levels (P < 0.05) of polyphenols and ascorbic acids were found in 'Bidan' (25.9 ± 1.3 mg GAE/g and 152 ± 10.4 mg/g DW, respectively), which also contained the highest levels of protocatechuic and vanillic acids. In addition, the level of antioxidant activity (μM TE/g DW) was significantly higher (P < 0.05) in 'Bidan' (121 ± 5.8, 109 ± 11.2, 102 ± 6.6 and 94 ± 4.7 for CUPRAC, ABTS, DPPH and FRAP radical scavenging assays, respectively). Pattern-recognition techniques (cluster analysis, principal component analysis, factor analysis, and canonical discriminant analysis) were used to compare the cultivars. A high correlation was found among the polyphenols (R2 = 0.99), ascorbic acid (R2 = 0.99+) and the antioxidant activity in the studied cultivars. In conclusion, the overall bioactivity of the cultivars was: 'Bidan' > 'Haenam' > 'Daeheung' = 'Hayward'. 'Bidan', a relatively new cultivar, can be recommended for consumption.