Analysis of derivatized and underivatized theanine enantiomers by high-performance liquid chromatography/atmospheric pressure ionization-mass spectrometry.
Theanine, a naturally occurring non-proteinic amino acid found in tea leaves, has demonstrated wide-ranging physiological activity, from lowering blood pressure to enhancing the anti-tumor activity of chemotherapeutic drugs. The chiral nature of theanine suggests that enantiospecificity plays a significant role in its various pharmacological functions. Using the Chirobiotic T (teicoplanin) chiral stationary phase, native and derivatized theanine enantiomers were separated and detected via high-performance liquid chromatography (HPLC) coupled to atmospheric pressure ionization mass spectrometry (API-MS). With the use of flow rates compatible with each ionization source, native theanine standards achieved excellent sensitivity and detection limits (10 ng/mL) for both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). Optimum sensitivity and detection limits for derivatized theanine standards were achieved using ESI-MS. The enantiomeric composition of six commercially available L-theanine samples was evaluated using the high-flow APCI-MS method and confirmed with photodiode array detection. Five of the six products contained significant amounts of D-theanine. Only one product, SunTheanine, appeared to contain only the L-theanine enantiomer.
Desai
Meera J
MJ
Department of Chemistry, Iowa State University, Ames, IA 50011, USA.
Armstrong
Daniel W
DW
D000277:Adjuvants, Pharmaceutic; D000959:Antihypertensive Agents / Q000032:analysis / Q000737:chemistry; D000970:Antineoplastic Agents; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005971:Glutamates / Q000032:analysis* / Q000737:chemistry; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism
D000277:Adjuvants, Pharmaceutic; D000959:Antihypertensive Agents; D000970:Antineoplastic Agents; D005971:Glutamates; C026166:theanine