The analytical method for the determination of phenolic compounds in rice varieties was developed. The
method consisted of extraction of phenolic compounds from rice before analysis by high performance
liquid chromatography (HPLC). Reversed phase HPLC equipped with photodiode array detection was
used and the separation condition was optimized. Under the optimum condition, twelve phenolic
compounds were separated within 24 min. Pressurized liquid extraction (PLE) was used to extract free
phenolic compounds from rice with the optimum extraction condition of 70% methanol and extraction
time of 15 min. While, bound phenolic compounds were extracted using alkaline hydrolysis for 15 min.
Six varieties of Thai rice including pigment and non-pigment rice in their brown and polished forms
were investigated. All of 12 phenolic compounds were detected as free phenolic compounds in all
samples. Ferulic acid was the most abundant free phenolic compounds in all samples, while ferulic acid
and p-coumaric acid were found as bound phenolic compounds in some samples. The content of
phenolic compounds, total flavonoid and antioxidant activity detected in pigment rice and brown form
were higher than non-pigment rice and polished form.