| Summary: | 碩士 === 國立宜蘭大學 === 食品科學系碩士班 === 104 === The purpose of this study was to investigate the change in phenolic composition of immature kumquat (Citrus japonica var. margarita) after in vitro gastrointestinal digestion and fermentation with lactic acid bacteria by LC/PDA/ESI/MS. In addition, the capability of elimination for methylglyoxal (MGO) will be also evaluated. Thus, the bioaccessibility and bioactivity of phenolic compounds after digestion and incubation could be elucidated and provide valuable information for the practical application. The results showed that flavonoids of immature kumquat, included C- glycoside, such as 3′, 5′ Di-C-b-glucopyranosylphloretin(DGPP), Acacetin 8-C-neohesperidoside (margaritene), and Acacetin 6-C-neohesperidoside(isomargaritene), and O-glycoside, such as Acacetin 7-O-neohesperidoside (fortunellin) and Isosakuranetin 7-O-neohesperidoside (poncirin). After gastric digestion, total flavonoids decreased about 25%. DGPP, a C-glycoside chalcone, decreased large magnitude about 29.3%.Besides the total flavonoids of O-glycoside, fortunellin and poncirin, reduced about 16.4-18.8%. However, margaritene and isomargaritene decreased just 4.7-8.7% after gastric digestion. The main reason might probably due to the effect of strict acid environment during digestion. After intestinal digestion, no obvious decrease of DGPP and fortunellin was observed. However, margaritene, isomargaritene, and poncirin decreased about 34%, 45%, and 30%,respectively. The bioaccessibility of flavonoids after intestinal digestion was between 23 and 33%, while DGPP was the major absorbed flavonoids. During gastrointestinal digestion, two new peaks were observed. One of these was named as Unknown 2, which was tentative identified as quinic acid. After gastrointestinal digestion and dialysis, the residue in the dialysis bag (known as unabsorbable) incubated with Lactobacillus (L. rhamnosus, L. plantarum, and L. paracasei) for 48 hours. Total flavonoids decreased significantly about 82% by L. plantarum incubation for 24 hours. The most decreasing flavonoid was DGPP to almost undetectable. The C-glycoside flavonoids, margaritene and isomargaritene, reduced 39% and 51%, respectively,while fortunellin and poncirin decreased also 66% and 34%, respectively. The flavonoids remained stable up to 48 hours. Similar changes were observed with incubation ofL. rhamnosus and L. paracasei. The flavonoids decreased drastically in 12 hours. The most decreasing one was DGPP, while the other flavonoids also decreased in 12 hours and remained stable up to 48 hours. Three new peaks were found after incubation, and the peaks Unknown 4 and 5 were tentative identified as derivatives of DGPP with hydroxyl groups.Immature kumquat, gastric digestion, and the absorbed compositions from intestinal digestion could react with MGO. The MGO elimination effects equal to 35%, 50%, and 70% aminoguanidine, respectively. After trapping MGO, total flavonoids of immature kumquat reduced about 90%, while gastric digestion of kumquat decreased about 40%. However, the flavonoids of intestinal digestion absorbed compositions of kumquat remained no obvious change. Therefore, it is proposed that either flavonoids or some other bioactivity compounds of kumquat possessed trapping ability of MGO. After digestion, the MGO elimination effects of kumquat is enhanced, which hinted the potential benefit to diabetes.In vitro fermentation by L. plantarum, total flavonoids of immature kumquat increased in 2 days. After that, it decreased or remained stable. It is suggested that flavonoids could be ease released from kumquat after fermentation with lactic acid bacteria, which lead to the increase of the flavonoids.
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