A Validated Method for Identification and Quantification of Anthocyanins in Different Black Rice (Oryza sativa L.) Varieties Using High-Performance Thin-Layer Chromatography (HPTLC).

Abstract

Introduction: Black rice (Oryza sativa L.) has gained prominence as a functional food because of its rich content of anthocyanins and polyphenols, offering potential health benefits. However, comprehensive research addressing the diverse anthocyanin compositions in black rice cultivars remains limited.

Objective: This study aimed to quantify anthocyanin contents, specifically kuromanin, cyanidin-3-glucoside, peonidin-3-O-glucoside, peonidin-3-glucoside chloride, and cyanidin-3-rutinoside chloride, in 150 rice varieties sourced from the North Eastern Region of India using a robust high-performance thin-layer chromatography (HPTLC) method.

Materials and methods: Rice grains of varying colors-black, orange-reddish, and white-were subjected to methanol extraction under dark conditions through cold maceration for 72 h. The resulting extracts underwent separation on HPTLC silica gel 60 F₂₅₄ plates utilizing an optimized mobile phase of ethyl acetate, 2-butanol, formic acid, and water (9:6:3:3::v/v/v/v).

Results: Anthocyanins were found to be present, and they were most visible in white light compared with UV light at 254 and 366 nm. They were analyzed via densitometry under white light illumination in transmission mode following development. Notably, anthocyanins were absent in grains of white and orange-reddish rice varieties, except for specific lines of Joha (JN 71, JN 83, JN 77, and JN 78) and all black rice variants. Among these, BR 15 exhibited the highest kuromanin content (74.14 ± 0.82 μg/mg), while BR8 showcased the highest peonidin-3-glucoside chloride concentration (27.59 ± 0.83 μg/mg).

Conclusion: This comprehensive analysis provides detailed insights into the anthocyanin compositions of 15 significant black rice cultivars, offering crucial data for breeding programs targeting enhanced anthocyanin-rich cultivars and the development of functional foods.