Characterization of the nutritional components in fruit and cladode of selenium-enriched nutraceutical cactus pear fruit varieties grown on agricultural sediment

Authors: Banuelos, Gary; STUSHNOFF, C - Colorado State University; Walse, Spencer; ZUBER, T - Colorado State University; PICKERING, I - University Of Saskatoon; GEORGE, G - University Of Saskatoon; YANG, S - University Of Saskatoon; FREEMAN, J - Fresno State University

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2012
Publication Date: 8/1/2012
Citation: Banuelos, G.S., Stushnoff, C., Walse, S.S., Zuber, T., Pickering, I., George, G., Yang, S.I., Freeman, J.L. 2012. Characterization of the nutritional components in fruit and cladode of selenium-enriched nutraceutical cactus pear fruit varieties grown on agricultural sediment. Food Chemistry. 135:9-16.

Interpretive Summary: Growers in the Westside San Joaquin Valley of California are attempting to identify new drought-tolerant crops because of strong reductions in available water supplies. To compound the problem, much of the area’s soils have accumulated high levels of salt, boron and selenium. We have identified three varieties of cactus (prickly-pear fruit) of different colors that were able to tolerate these adverse soil conditions. Fruit and cladodes were sampled from each variety and the following nutritional parameters were evaluated: mineral nutrient content, chemical forms of selenium, total phenolics, vitamin C and antioxidant status. Results show that fruit and cladodes grown in the poor quality soils exhibited the following: 1) accumulated more nutrients, including selenium 2) exhibited higher total phenolics in red and orange fruit; 3) exhibited no signifcant effect on vitamin C content, and 4) increased free radical activity (antioxidant activity) in orange fruit and their cladodes. This work demonstrates some of the biochemical changes that occur in different varieties of salt and boron tolerant cactus (prickly-pear fruit products) grown in poor quality soils compared to the same plants grown under good quality soil conditions. Importantly, we present the potential of growing this new crop and producing selenium-biofortified plant products, which possess enhanced nutritional characteristics.

Technical Abstract: Different accessions of different colored cactus pear (Opuntia ficus Indica) were grown in soils high in salts, boron and selenium (Se) located in the Westside of central California. The changes in the nutritional status and biological transformation of the absorbed inorganic Se from the soils into organic forms of Se within cactus plant parts are plant responses that may lead to producing a valuable nutra-ceutical food crop from poor quality soils. In order to evaluate changes in selected nutritional parameters, we employed, a suite of analytical procedures for testing fruit and cladodes from Opuntia grown in control and in poor quality soils for the following: 1) mineral nutrient; 2) chemical forms of Se; 3) total phenolics; 4) vitamin C, and 5) antioxidant status (free radical scavenging capacity). Our results showed that fruit and cladodes among the three different accessions (purple, orange, red) accumulated a mean of 2.6 and 7.8 mg Se/kg DM, respectively. High resolution Se speciation using proteinase XIV aqueous extractions and pressure liquid chromatography coupled to ICP-MS identified the highest percentages of soluble Se forms in fruit and cladodes as selenomethionine (SeMet), methylselenocysteine (MeSeCys), selenate and selenocystathionine (SeCyst). Red and orange fruit from cactus grown in poor quality soil contained significantly more total phenolics than control-grown, while no differences were observed in cladodes. Vitamin C content was slightly elevated in control grown fruit and cladodes from all accessions compared to those obtained from plants grown in poor quality soil. Only orange fruit and cladodes from purple in and red fruit producing plants exhibited a significant increase in free radical scavenging capacity when grown on poor quality soil compared to some plants grown on control soils. Overall, these results are the first to report on the different nutritional characteristics of Se and the other biochemical changes in fruit and cladodes from different accessions (based upon fruit color) of Opuntia grown under high salinity, boron, and selenium conditions. Moreover, we clearly present the potential advantages of growing this new alternative crop under adverse soil conditions and producing Se-biofortified and nutritional-enhanced fruits and cladodes as new potential nutra-ceutical food products.