Antioxidant Properties of Cultivars and Selections from the Colorado Potato Breeding Program

Abstract

Consumers have become increasingly aware of potential health benefits from diets rich in fruits and vegetables. While potato has not yet surfaced as a headline-grabber in this respect, there is increasing evidence that some genotypes may possess health attributes that warrant attention. Plant breeders rely on germplasm biodiversity to advance their programs and are also acutely aware of current marketing trends that relate to health attributes. Investigations of antioxidant properties for over 90 genotypes were conducted to characterize antioxidant profiles for the Colorado potato breeding program and to identify those especially rich in antioxidants. The objective was to summarize data based on total phenolics (TP), Trolox equivalent antioxidant capacity (TEAC) and vitamin C, as well as to provide LC/MS characterization of major phenolic compounds and glycoalkaloids for pigmented genotypes. Preliminary data from breast cancer cell culture inhibition studies were examined for relationships to in vitro chemical assays. Genotypes with red or purple skin and flesh consistently had the highest gallic acid equivalent TP, TEAC, and chlorogenic acid content. Baked tubers had lower TP levels, TEAC and vitamin C compared to uncooked, microwave cooked and boiled tubers. Environmental effects contributed year to year variation in TP and TEAC radical scavenging capacity. TP content increased after 6 to 7 months in refrigerated storage at 5 ± 1°C in several highly pigmented, but not in white or yellow fleshed cultivars and selections. Major phenolic compounds, anthocyanins, and glycoalkaloid content were further investigated with LC/MS in six cultivars. The pigmented cultivars ‘Purple Majesty’ and ‘Mountain Rose’ contained considerably higher levels of chlorogenic acid isomers than the non-pigmented genotypes. In the non-pigmented genotypes, chlorogenic acid and glycolalkaloid content were highest in ‘Rio Grande Russet’. Chlorogenic acid has been demonstrated to exhibit several desirable anticarcinogenic properties in recent biochemical investigations, as have several of the phenolic based anthocyanin pigments found in many colorful fruits and vegetables. Thus, comprehensive compositional profiles using LC/MS are of interest in characterizing germplasm for breeding purposes. Preliminary tests with phosphate buffered saline (PBS) extracts of baked tubers from six cultivars revealed that ‘Rio Grande Russet’ was most effective in inhibiting growth of breast cancer cultures MCF-7 and MDA-MB-468. ‘Purple Majesty’ inhibited to some extent, ‘Mountain Rose’ and ‘Yukon Gold’ had no inhibitory effect. A subsequent study with 21 genotypes where the initial extract was made with 80% acetone followed by drying and extraction in aqueous PBS differed from direct PBS extraction. Five genotypes including ‘Russet Nugget’ inhibited at 0.187% to 0.375% w/v of the cell culture solution. However, IC50 inhibition data was not strongly related to the in vitro chemical data for these cultivars.