Table I.

Retention times and HPLC-PDA data of stereoisomeric betaxanthins (derived from Gly, (S)-amino acids, and amines), BA, and betanin

Amino Acid/Amine	Solvent System 1			Solvent System 2
	Rt		HPLC-PDAa	Rt		HPLC-PDAa
	2S/S	2S/R		2S/S	2S/R
	min		λmax (nm)	min		λmax (nm)
His	8.6	8.4	472	5.3	5.4	477
Lys	9.5		468	5.0	5.3b	475
Asn	10.6		469	4.4	4.6	472
Ser	11.1		466	3.9		474
Arg	11.5		468	8.0	8.3	475
Cystine	12.0	11.9c	475	5.6	6.0d	475
Gln	12.0		468	6.0	6.4	475
Asp	12.5	12.3	467	3.4		474
Hyp	12.6		480	4.3	4.7	481
Gly	12.7e		465	6.0e		472
Thr	13.5	13.3	468	6.2	6.5	475
Citrulline	14.7	14.5	467	8.6	8.8	475
Glu	14.9	14.7	468	7.7	8.0	475
Ala	17.4	16.7	465	8.5	8.7	474
Pro	19.8	19.3	477	10.5	10.0	485
−(BA)	21.8		405	9.6		425
Dopa	22.3	22.1	470	12.4		477
CDGf(betanin: isobetanin)	22.7	24.1	538	14.0	16.3	536
Dopamine	24.7e		457	18.1e		474
Tyr	25.2	24.8	469	19.4		473
Val	26.4	25.0	467	12.9	12.5	475
Met	26.4	25.3	468	13.3	12.7	476
Tyramine	29.3e		459	20.5e		469
Ile	33.0	31.5	466	16.1	15.8	475
Leu	34.0	32.7	468	16.4		476
Phe	34.5	33.3	472	18.2	17.9	477
Trp	37.3	36.8	472	19.8	18.1	478

BA extracted from hydrolyzed betanin:isobetanin mixture (2:1) was added to different (S)-amino acids and amines. After workup (see Methods) the betaxanthins were analyzed by HPLC (solvent systems 1 and 2). When only one R_t is given for an isomer pair, the separation was not achieved.

^aλ_max of the (2S/S)-form. 

^bAdditional peak at R_t 8.6 min (λ_max 469 nm). 

^cAdditional peak at R_t 29.8 min (λ_max 474 nm), cystein yielded with BA two compounds, R_t 17.2 and 18.1 min (both λ_max 497 nm). 

^dAdditional peak at R_t 19.4 min (λ_max 474 nm), cystein yielded with BA two compounds, R_t 7.9 and 9.9 min (both λ_max 495 nm). 

^eOnly S- and R-isomers of the BA moiety. 

^fCDG, cyclo-Dopa 5-O-glucoside.