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Triterpenoid Saponins quantification from Quinoa (Chenopodium Wild) by UV-Vis/GC-MS
I. MEDINA MEZA (1), N. Aluwi (1), S. Saunders (2), G. Ganjyal (1) (1) School of Food Science, Washington State University, Pullman, WA, U.S.A.; (2) 2The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, U.S.A..

Quinoa (<i>Chenopodium quinoa</i> Willd) is an Andean crop with high nutritional value. Saponins are the phytochemicals found in the external layers of quinoa seeds (between 2-5%), conferring bitter flavor that is not desirable by consumers. Quantification of saponins is challenging, since they are a complex mixture of triterpene glycosides that are derivatives from ß-amyrin (<i>3ß</i>-Olean-12-en-3-ol). An attempt was to quantify the total triterpenoid saponins in 28 varieties of quinoa, developing a rapid extraction protocol coupled with a UV-Vis/GC-MS quantification method. The total saponins were quantified using a calibration standard curve of oleanolic acid at ? = 527 nm. The total saponin content (expressed as % oleanoic acid equivalent) ranged from 0.67% (BBR variety) to 3.09% (Red Head variety). Seven varieties were classified as low-saponin content >0.11% whereas 21 varieties were classified as bitter genotypes. A commercial variety (Black) was used as reference (2.7%). Oleanolic acid (OA), hederagenin (HD), serjanic acid (SA) and pytoalaccagenic acid (PA) were identified by GC-MS. PA was the most abundant sapogenin in all samples ranged from 40 to 80% of total content, followed by HD with 15-30%. The formation of PA and the total sapogenin content had a positive correlation of <i>R2=0.88</i>. This method reduces time and costs associated with extraction steps. Organic solvent-assisted washing and analytical fractionation were substituted by a hydrolysis step, followed by a liquid/liquid partition, which dramatically decreased the amount of organic solvent used. In conclusion, this methodology presents a potential alternative for a high sensitive quantification of total saponin in quinoa.