In vivo lipid oxidation generates hydroperoxides, which are implicated in various diseases. Therefore, understanding the underlying mechanisms of lipid oxidation is essential for preventing its further process. One effective approach to inhibit this process is employing antioxidants. Among them, polyphenols are recognized as promising candidates for suppressing the oxidation. Our studies have identified several potential polyphenolic compounds using precise analysis; advanced mass spectrometry techniques, combined with several analytical methods. Notably, we discovered novel source of γ-oryzanol (OZ) isomers, particularly as 24-methylenecycloartanyl ferulate (24MCA-FA), which were previously thought to exist exclusively in rice but were also detected in barley. Another new isomer of 24MCA-FA, particularly 24-methylenecycloartanyl caffeate (24MCA-CA) was also discovered in barley, which was reported for the first time in our study. Additionally, we discovered newly identified of 24MCA-FA isomers—cyclobranyl ferulate (CB-FA) and cyclosadyl ferulate (CS-FA)—present in rice bran oil and processed foods containing it but absent in rice bran itself. These findings demonstrate the strength of mass spectrometry in precisely identifying and exploring unique molecular species of polyphenols, particularly OZ. The studies also open new opportunities for further investigation into the antioxidant potential of OZ isomers, thus supporting the development of next-generation functional foods for in vivo efficacy.