Development and validation of a novel HPLC-UV method for quantifying vitamin D forms and precursors in vegetable oils after exposure to sunlight and UV radiation

Abstract This study presents the development and validation of a robust HPLC-UV method for the simultaneous detection and quantification of vitamin D 2 , vitamin D 3 , ergosterol, and 7-dehydrocholesterol in a single analytical run, adhering to ICH Q2 (R1) guidelines. Application of the HPLC-UV method to six vegetable oils demonstrated inherent vitamin D content and its enhancement under different radiation conditions. Oils were exposed to direct sunlight, UVA, and UVB radiation, with UVB showing the most significant impact on vitamin D levels. Notably, UVB exposure increased vitamin D 3 in castor oil from 2.82 μg mL −1 to 4.29 μg mL −1 and vitamin D 2 in mustard oil from 0.73 μg mL −1 to 1.89 μg mL −1 . The findings highlight the potential of UVB radiation to convert vitamin D precursors to active forms more effectively than other radiation sources. This study provides a novel approach for naturally enriching vitamin D in vegetable oils, offering a promising strategy to mitigate vitamin D deficiencies in populations with limited sun exposure or dietary restrictions. The developed HPLC-UV method and resultant insights into the radiation-induced enhancement of vitamin D content in oils contribute valuable knowledge to nutritional science.