Effect of Preheating Processing on Antioxidant and Immunomodulatory Properties of Black Rice Extracts

• Main Authors: Yu-Hsiang Hsu, 徐鈺翔
• Other Authors: Cheng-Kuang Hsu
• Format: Others
• Language: en_US
• Online Access: http://ndltd.ncl.edu.tw/handle/42677476028162707261

碩士 === 國立嘉義大學 === 食品科學系研究所 === 103 === It has been shown that black rice possess antioxidant and anti-inflammatory activities. Researchers also found that preheating processing can increase antioxidant activities of some plants. This study investigated the effect of preheating processing on the antioxidant and immunomodulatory properties of black rice (Oryza sativa L) (Zijing rice). The preheating treatment groups included: the un-preheated control, black rice baked at 130℃ for 5 (B130-5), 10 (B130-10) and 20 (B130-20) minutes, black rice baked at 170℃ for 5 (B170-5), 10 (B170-10) and 20 (B170-20) minutes, microwave heated black rice at 10P for 30 (M10P-30s) and 60 seconds (M10P-60s), and 30P for 30 (M30P-30s) and 60 seconds (M30P-60s). Preheated black rice was extracted with 90℃ hot water at a solid-liquid ratio of 1:15 in a 90℃ water bath for 30 minutes, centrifuged at 9433 g. The supernatant was collected for the analysis of total phenolic content (TPC), total flavonoids content (TFC), total anthocyanin content (TAC), DPPH radicals scavenging capability, reducing power and ferrous ions chelating activity. The results showed that B170-20 contained the most abundant TPC and TAC compared with others, while its TFC was no significant difference compared with the control. In addition, the ferrous ions chelating activity and reducing power of B170-20 were significantly higher than those of the control. Therefore, the black rice baked at 170℃ for 20 minutes (notated as BBR; Baked black rice) was selected and compared with the un-preheated control (UBR; Un-preheated black rice) to investigate the effect of baking processing on the anthocyanins component and antioxidant properties of black rice extracted using various solvents. The anthocyanins in the hot water extracts of black rice were measured by a high-performance liquid chromatography, and the results showed BBR was higher than UBR in cyanidin-3-glucoside and peonidin-3-glucoside. UBR and BBR were extracted by 40, 80% ethanol, 40, 80% acetone, cold water and hot water. The highest TPC, TFC and TAC were obtained from UBR extracted by 80% acetone, and the highest DPPH radicals scavenging capability and reducing power could be obtained from UBR and BBR by 80% acetone extraction followed by hot water extract of BBR. In both 40% and 80% ethanol extracts, BBR was higher than UBR in TPC, TFC and TAC. The hot water extracts of BBR was also significantly higher than UBR in TAC but no significant difference in TPC. Furthermore, the hot water extracts of BBR was significantly higher than UBR in DPPH radicals scavenging capability and reducing power. To investigate the effect of the baking process on immunomodulatory properties of the hot water extracts from black rice, RAW 264.7 macrophages was used as the cell model. UBR or BBR pretreatment inhibited NO production and intracellular ROS production in lipopolysaccharide (LPS)-stimulated macrophages, and especially BBR was stronger than UBR in NO inhibition. However, UBR or BBR co-treatment with LPS did not inhibit TNF-α, IL-1β and IL-10 production in LPS-stimulated macrophages, while UBR or BBR treatment alone activated RAW 264.7 macrophages to produce NO, TNF-α, IL-1β and IL-10. In conclusion, the baking process (at 170℃ for 20 minutes) could be used to promote antioxidant properties of the hot water extract from black rice, and the hot water extracts of black rice possessed dual immunomodulatory properties in RAW 264.7 macrophages.