Plant materials

The used materials were CNU hybrids described in Table 1. and cultivation methods were same as contents reported in J. of Crop Sci. 60(2) (Na et al., 2015).

Determination of antioxidant activity

Pre-treatment of samples

The used hybrid corn kernels that were used for physicochemical analysis were immediately frozen after sampling and lyophilized in freeze dryer at 5 μm Hg pressure and –80°C. Samples were pulverized using a disintegrator and sifted through a 24-mesh sieve. Samples from each corn hybrid were sealed in a plastic bag and kept at –20°C. The supernatant was filtered through Whatman No.1 filter paper and was concentrated using a rotary evaporator. The concentrated solutions were used for assessing antioxidant activities.

Measurement of antioxident

The free radical scavenging activity of extracted sample in the colored waxy corn hybrids was measured by the DPPH method proposed by Blosis (1958).

An SOD assay kit (Dojindo Laboratories) was used to determine the SOD activity. The anthocyanin content was determined according to the method described by Yang (2008) with modifications. The carotenoid content of corn kernel was estimated by the method described by Handelman (1996).

Statistical analysis

Mean difference of functional components on the used hybrids were compared using the SAS program (v. 9.3).

DPPH radical scavenging

DPPH radical scavenging activity estimated to determine the antioxidant activity of the waxy corn hybrids (Table 1). The average DPPH radical scavenging activity in colored waxy corn was 22. CNU13H-44 among hybrids showed as a highly 261% than check. In white corn, CNU13H-73 showed a higher activity than the control. Most of the yellow corn hybrids was higher than that of the control hybrid except CNU13H-40. The purple CNU13H-75 hybrid appeared to have a high DPPH radical scavenging activity as a 181%, and was followed by CNU13H-75 and CNU13H-46. Yu et al. (2006) reported that phenolic compounds have been reported to inhibit damages in the body caused by free radicals because it has a potent capability of reducing free radicals. Lee et al. (2006) and Lee et al. (2005) reported that colored waxy corn has been reported to contain more antioxidants than colorless corn and has superior DPPH radical scavenging activity.

SOD anion radical scavenging activity

SOD activity of the colored waxy corn hybrids showed in Table 2. The SOD activity ranged from 15.6 mg/g to 32.7 mg/g. Among the hybrids, CNU13H-44 showed the highest SOD activity (32.7 mg/g) and was followed by CNU13H-29, which showed an SOD activity of 31.8 mg/g. CNU13H-3 with a white colored hybrid and CNU13H-44 and CNU13H-29 with yellow colored hybrids showed high SOD activities, but SOD activity of most purple colored hybrids showed lowly than control hybrids. About these facts, Li et al. (2008) reported that reducing suoeroxide anion radical is significantly useful for human health.

Anthocyanin pigment content

The anthocyanin content of the 28 hybrids was detected at 530 nm (Table 3). Among the hybrids, the purple colored waxy corn hybrids including CNU13H-75, CNU13H-77 and CNU13H-74 had higher than the control hybrid, Miheukchal. These hybrids had estimated anthocyanin contents of 0.219 mg/g, 0.181 mg/g, and 0.168 mg/g, respectively. Additionally, CNU13H-27 as a white hybrid, and CNU13H-71 as a yellow hybrid, had high anthocyanin contents. These facts were same an other reports (Kim et al., 2005) They reported that five types of pigments were separated in black corn, especially, C3G level was higher than other pigments.

Carotenoid pigment content

The carotenoid pigment content in the CNU 28 waxy corn hybrids was analyzed at 420 nm (Table 4) according to the method described by Handelman. The carotenoid content of corn kernel varied regardless of color corn. Among the hybrids, the carotenoid content in the yellow colored corn (4.6 mg/g) was higher than that in the purple and white colored corn. Especially, CNU13H-71 of yellow hybrid had the highest carotenoid content of 12.6 mg/g, and CNU13H-73, a white hybrid, had the lowest a carotenoid content of 3.0 mg/g. Lambert et al., (1990) and Mayne (1996) reported that carotenoid is a natural pigment that is typically distributed widely in nature and is mainly included in red and yellow colored vegetable crops.