Effects Of Processing On Phytochemicals Profiles And Biological Activities Of Sorghum Grain

Sorghum (Sorghum bicolor (L.) Moench), the fifth leading cereal crop in the world, is one of theimportant upland crops in China. Sorghum contains various phytochemicals such as procyanidins,phenolic acids, anthocyanins, which are concentrated in the outer layers of the sorghum grains (pericarpand testa). Epidemiological studies have shown that increased consumption of whole grains and theirproducts is associated with reduced risk of developing chronic diseases, such as cardiovascular disease,type II diabetes, obesity, and cancer.We use the normal phase of HPLC to investigate the sorghum procyanidins oligomers after purifiedby AB-8macroporous resin. The characterization and detection of sorghum procyanidins oligomerswere performed on Waters2695liquid chromatograph system equipped with UV and fluorescencedetectors. The mobile phase consisted of (A) dichloromethane/methanol/water/acetic acid (82:14:2:2)and (B) dichloromethane/methanol/water/acetic acid (10:86:2:2).In this study, ESI-MS full-scan analyses exhibited ions at m/z288.9,577.0,865.1,1153.3,1441.3,and1728.9for fractions P1, P2P3, P4, P5, and P6, respectively, corresponding to the deprotonatedmolecular ions [M-H] of procyanidin oligomers from monomer to hexamer. Additionally,thecontribution of the individual oligomers to the total procyanidins was calculated by the peak areameasurement.In order to make the attractive and high quality sorghum tea, we design the different processingconditions to obtain the optimum processing. Generally, the processing are as follows: for soaking, theraw whole sorghum grains were soaked in distilled water (1:8w/v) for1h at room temperature, thesample then was drained, washed and dried. For steaming, the soaked sample was steamed for20min.While for roasting, the steamed sample was roasted at150C for1h using the rotating oven.The effect of processing on phytochemicals and bioactivities of sorghum grains were performed. Inthis study, the total phenolc content (TPC), total flavonoid content (TFC), procyanidins content (PAC)and phenolic acids (free and bound) of the extracts from raw and processed sorghum grain weredetermined. Complex changes in chemical compositions occurred during processing. Followed by thechanges of phytochemicals of sorghum grains, there are significant （p <0.05） differences ofantioxidant activity, α-glucosidase and α-amylase inhibitory activities based on the processing. Thelinear correlation coefficients between phytochemicals (TPC, TFC and PAC) and bioactivities ofextracts from sorghum grain were evaluated. In our study, we found that procyanidins have the strongestcorrelation (r=0.979, r=0.968, r=0.912, p <0.0001, respectively) with antioxidant activity,α-glucosidase and α-amylase inhibitory activities.