Harvest Age Effect on Phytochemical Content of White and Black Glutinous Rice Cultivars

Many studies have been conducted on the bioactive compounds of rice seeds, however, there is limited information on the bioactive compounds of rice sprouts. This study focused on the age effect on the phytochemical content of white and black glutinous rice sprouts harvested between 5 and 25 days old. We assessed yield, total phenolic content, total flavonoid content, total anthocyanin content, total chlorophyll content, and proximate analysis. HPLC results identified protocatechuic acid, vanillic acid, and rutin in the sprouts of both cultivars, ranging between 0.56–1.58, 0.65–7.69, and 0.47–1.68 mg/g extract, respectively. The amount of bioactive compounds and proximate compositions in black glutinous rice were generally higher than white glutinous rice in an age-dependent manner (p < 0.05). At 5–7 days, black glutinous rice contained the highest total anthocyanin content, while white glutinous rice contained the highest total phenolic content and total flavonoid content (p < 0.05). High total chlorophyll content was initially detected in white glutinous rice at a younger age than black glutinous rice (p < 0.05), while total chlorophyll content in both cultivars was not significantly different. Our study confirms the presence of phytoconstituents in the rice sprouts of white and black glutinous rice and their potential as functional foods and for being further development as natural health products.