Rice varietal differences in bioactive bran components for inhibition of colorectal cancer cell growth

• Rice bran extracts differentially inhibit colorectal cancer (CRC) cell growth.
• Different rice varieties have unique lipophilic bioactive compounds.
• Total soluble phenolic content was correlated with CRC cell inhibition.
• Vitamin E isoforms γ-T3, α-T3, and α-T were correlated with CRC cell inhibition.
• Rice bran chemoprevention is due to the complex phytochemical mixture.

Rice bran chemical profiles differ across rice varieties and have not yet been analysed for differential chemopreventive bioactivity. A diverse panel of seven rice bran varieties was analysed for growth inhibition of human colorectal cancer (CRC) cells. Inhibition varied from 0% to 99%, depending on the variety of bran used. Across varieties, total lipid content ranged 5–16%, individual fatty acids had 1.4- to 1.9-fold differences, vitamin E isoforms (α-, γ-, δ-tocotrienols, and tocopherols) showed 1.3- to 15.2-fold differences, and differences in γ-oryzanol and total phenolics ranged between 100–275 ng/mg and 57–146 ng GAE/mg, respectively. Spearman correlation analysis was used to identify bioactive compounds implicated in CRC cell growth inhibitory activity. Total phenolics and γ-tocotrienol were positively correlated with reduced CRC cell growth (p < 0.05). Stoichiometric variation in rice bran components and differential effects on CRC viability merit further evaluation elucidate their role in dietary CRC chemoprevention.