Identification of Betalains from Petioles of Differently Colored Swiss Chard (Beta vulgaris L. ssp. cicla [L.] Alef. Cv. Bright Lights) by High-Performance Liquid Chromatography−Electrospray Ionization Mass Spectrometry

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Abstract
The betalain pattern of differently colored Swiss chard (Beta vulgaris L. ssp. cicla [L.] Alef. cv. Bright Lights) was investigated for the first time. Nineteen betaxanthins and nine betacyanins were identified by RP-HPLC and positive ion electrospray mass spectrometry, co-injection experiments with semisynthetic reference compounds, and standards derived from authentic plant material, respectively. Histamine−betaxanthin and alanine−betaxanthin were found to be novel betaxanthins, which to the best of our knowledge have not been reported as natural compounds until now. Furthermore, tyramine−betaxanthin (miraxanthin III) and 3-methoxytyramine−betaxanthin, which to date were known only from families other than the Chenopodiaceae, were detected for the first time in colored Swiss chard. The betacyanin pattern of purple petioles was composed of betanin, isobetanin, betanidin, and isobetanidin. Although phyllocactin was present in only trace amounts, further acylated structures such as betanidin−monoferuloyl-5-O-β-diglucoside and lampranthin II, accompanied by their corresponding C15-epimers, were identified. In addition, quantification of betalains and CIE L*C*h° measurements were performed with the colored extracts to correlate the visual appearance with the respective pigment patterns. Besides the novel phytochemical findings, the present study is useful for the evaluation of betalainic Swiss chard as a potential coloring foodstuff. Keywords: Chenopodiaceae; Beta vulgaris; colored Swiss chard; betalains; betaxanthins; acylated betacyanins; coloring foodstuff