Primary and Phenolic Metabolites Analyses, In Vitro Health-Relevant Bioactivity and Physical Characteristics of Purple Corn (Zea mays L.) Grown at Two Andean Geographical Locations

Abstract

Purple corn (Zea mays L.) is native to the Andean region, but limited research has been performed about the potential metabolic variability when grown under Andean environmental conditions. This study was aimed at evaluating the phenolic and primary polar metabolites composition of purple corn (kernels and cobs) grown at two Peruvian Andean locations (lowland and highland) using targeted UHPLC (ultra-high-performance liquid chromatography) and untargeted GC-MS (gas chromatography mass spectrometry) metabolomic platforms, respectively. Changes in the physical characteristics and the in vitro bioactivity were also determined. Purple corn from the highland zone showed higher contents of ash, crude fiber, total phenolic contents, DPPH (2,2-diphenyl-1-picrylhydrazyl) antioxidant capacity, and α-amylase inhibitory activity in kernels, whereas increased levels of flavonoids (anthocyanins and quercetin derivatives) and ABTS [2,2ʹ-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] antioxidant capacity were observed in cobs in comparison to lowland samples. No effect of the Andean location was found on the α-glucosidase inhibitory activity relevant for hyperglycemia management, while yield-linked physical characteristics were high in purple corn grown at the lowland zone. Polar primary metabolites related to the carbohydrate (monosaccharides, sucrose, and d-sorbitol), amino acid (valine and alanine), and tricarboxylic acid cycle (succinic, fumaric, and aconitic acid) metabolism were higher in highland purple corn (cob and kernel) likely due to abiotic stress factors from the highland environment. This study provides the foundation for further breeding improvements at Andean locations.

Diversity of the Peruvian Andean maize (Zea mays L.) race Cabanita: Polyphenols, carotenoids, in vitro antioxidant capacity, and physical characteristics

“…The anthocyanin concentrations found in Cabanita maize agree with the amounts reported by Paulsmayer et al ( 54 ) (0.3–12.8 mg/100 g DW of total anthocyanins with a HPLC method) in diverse pink aleurone maize germplasm from Mexico and the United States with similar kernel pigmentations as those observed in Cabanita maize samples ( Figures 1 , 2 ). Partially red-pigmented kernels in some evaluated samples indicate lower anthocyanin contents in comparison to purple pericarp-pigmented maize ( 18 ).…”

“…The free and bound phenolic fractions were extracted from the powdered maize samples following the methodology of Ranilla et al ( 18 ) and Ranilla et al ( 24 ). A mix of 0.1% HCl methanol/acetone/water (45:45:10, v/v/v) was used for the extraction of the free phenolic compounds.…”

“…A mix of 0.1% HCl methanol/acetone/water (45:45:10, v/v/v) was used for the extraction of the free phenolic compounds. An alkaline hydrolysis with 3 N NaOH was applied on the free phenolic extraction residue for the release of the bound phenolic fraction ( 18 , 24 ). Final aqueous extracts were kept at –20°C until further analysis.…”

“…Phenolic compounds were separated using a Kinetex C18 analytical column (100 × 2.1 mm i.d., 1.7 μm) with a Kinetex C18 guard column (5 × 2.1 mm i.d., 1.7 μm) (Phenomenex Inc., Torrance, CA, USA). The binary gradient elution with 0.1% formic acid and acetonitrile mobile phases, and chromatographic conditions were the same as used previously by Ranilla et al ( 18 ) and Vargas-Yana et al ( 32 ). The chromatograms and peaks were processed using the Chromeleon SR4 software version 7.2 (Thermo Fisher Scientific).…”

“…In case of Peru, research has been focused mostly on purple maize ( Kculli race) because of its high content of anthocyanins ( 16 , 17 ). Different studies have reported the phenolic composition of Peruvian purple maize and highlighted its associated bioactivity such as the antioxidant, antimicrobial, anti-hypertensive, and anti-cancer potential ( 18 – 23 ). However, limited information exists about the bioactive composition of other Peruvian maize races.…”