SPDS Lutein and Turmeric ERPs

General Information

Reviewer Name:

Neal Craft

Email:

ncraft@crafttechnologies.com

Organization:

Craft Technologies

Method Reviewed:

LUT‐02

Method Title:

Determination of Lutein and Zeaxanthin Esters and Their Geometric Isomers in  Carotenoid Ester Concentrates Used as Ingredients in Nutritional Supplements:  Validation of a Combined Spectrophotometric‐HPLC Method

Applicable SMPR

2016.004

Information about the Method Only

Summary of Method:

The method uses a combination of spectrophotomety to measure total carotenoids  and normal‐phase HPLC on a saponified sample to estimate the percentage of free  lutein and zeaxanthin content in carotenoid ester concentrates, including their main  geometrical isomers. The unique part of this method is the estimate of a composite‐ specific absorbance due to the differing absorbances of the geometric isomer  distribution. The method is reportedly applicable to carotenoid ester concentrates in  oil suspensions and dosage forms. The sample is first dissolved in hexane–2‐ propanol (95+5, v/v) for spectrophotometric measurement at the maximum  absorption wavelength of ~445 nm. Subsequently, a sample is saponified then  separated using normal‐phase HPLC to determine the relative percentage of the  main geometric isomers of lutein and zeaxanthin. The method is reportedly applicable to carotenoid ester concentrates in oil  suspensions and dosage forms.  The method principles are sound. Normal‐phase chromatography is an excellent  method to separate xanthophylls and geometric isomers. Spectrophotometry has  been used for decades to estimate carotenoid content. The specific addition in this  method is to account for geometric isomer distribution of the samples and adjust  the calculation of content for the specific isomer content. This should result in a  more accurate estimate of xanthophyll esters. It makes some the assumption that  saponification does not alter the original isomer distribution of the esters. The execution of the method is adequately clear. The calculation is more  complicated and makes some assumptions that may not be accurate or  substantiated. Normal‐phase HPLC is a good method to separate the xanthophylls.  Spectrophotometry is a simple straight‐forward measurement of total carotenoids.  There is an effort to more accurately assess the xanthophyll content. There are assumptions made that could bias the results. Total carotenoids includes  everything that absorbs at 445nm. This could include hydrocarbon carotenes and  more polar xanthophylls which may not be accounted for by the HPLC. It assumes  that the saponification does not alter the isomer distribution which is incorrect. The  calculation of composite‐specific absorbance is theoretically sound but may not be  fully substantiated with foundational data. It assumes a single fatty acid ester and  uses E1% values that are not well documented or generally accepted. The HPLC  conditions are not current technology. Use of neat lutein and zeaxanthin standards  would be beneficial. Method is limited to lutein and zeaxanthin ester products. It  does not include beta‐cryptoxanthin or beadlet products.

Method Scope / Applicability

General Comments About the  Method

Method Clarity

Pros / Strengths

Cons / Weaknesses

Review of Information in Support of the Method

General Comments about  Supporting Data

There is a substantial amount of precision , linearity and selectivity data from a  single lab.

Method Optimization

There is no discussion of HPLC or saponification optimization.