Comparative Analysis of Glucosylceramide, Steryl glucoside, and Cytotoxicity in Rice Bran Extracts from Hom Pathum and Riceberry

Abstract

This study evaluated residual methanol levels, lipid class distribution, and the glucosylceramide (GlcCer) and steryl glucoside (SG) contents of rice bran extracts from Hom Pathum (HP) and Riceberry (RB) cultivars and assessed the cytotoxicity of the GlcCer- and SG-enriched extracts using skin-relevant cell models. Rice bran from both cultivars was sequentially extracted with ethyl acetate followed by methanol. Residual methanol in crude extracts was quantified using headspace GC–MS. Total lipids were fractionated by solid-phase extraction into neutral lipids (NL), glycolipids (GL), and phospholipids (PL), and the GL fraction was analyzed by thin-layer chromatography with image-based quantification to determine GlcCer and SG contents. The RB extract, which showed higher glycolipid content, was selected for cytotoxicity testing using a resazurin reduction assay in HaCaT keratinocytes and BJ fibroblasts. HS-GC–MS results confirmed that residual methanol was below 10 ppm in all extracts, meeting international safety guidelines. Lipid profiling revealed clear varietal differences: HP bran was dominated by NL (90.3% w/w), whereas RB contained higher proportions of GL (14.3% w/w) and PL (17.3% w/w). GlcCer (3.08% of GL; 0.027% w/w of bran) and SG (6.34% of GL; 0.055% w/w of bran) were detected exclusively in RB. In vitro assays showed that RB extract was non-cytotoxic to HaCaT and BJ cells at 6.25–50 µg/mL and increased fibroblast viability (113-114%) at 100-200 µg/mL. Overall, the findings indicate that Riceberry bran provides a safe, GlcCer-rich lipid extract with potential dermal benefits. This integrated assessment identifies Riceberry bran as a promising source of functional sphingolipids for nutraceutical, cosmeceutical, and topical applications.