Research On The Enrichment Of Sulforaphane In Postharvest Broccoli And Its Protective Effect On Intestinal

Broccoli is a nutritious and healthy vegetable which belongs to the cruciferous family and contains a lot of antioxidants such as ascorbic acid and polyphenols.Broccoli is rich in a variety of isothiocyanates,among which sulforaphane(SFN)is the natural phytochemical ingredient with the best anti-cancer effect,and it also has anti-inflammatory and other physiological effects.Postharvest broccoli is prone to senescence and yellowing,and the loss of nutrients will seriously affect its quality and commercial value.Melatonin is an indoleamine hormone that is widely present in living organisms,it has the ability to enhance the antioxidant capacity of fruits and vegetables after harvest by scavenging free radicals to delay senescence.However,the effect of melatonin on the SFN production and quality of fresh-cut broccoli during cold storage was unclear.In view of the characteristics of the sulforaphane production system,physical processing methods such as high pressure processing(HPP)and microwave(MW)can be used to treat broccoli,and it has practical significance to study their combined effect on the sulforaphane production system,and there is no relevant research in this area.Chemotherapy drugs such as 5-fluorouracil(5-Fu)can cause many side effects such as intestinal mucositis.It is currently known that SFN and 5-Fu have a synergistic anti-cancer effect,and the effect of SFN on intestinal mucositis caused by 5-Fu is unknown.This article mainly carried out research work from the above aspects to provide experimental basis for the post-harvest enrichment and physiological functions of SFN in broccoli.1.Storage temperature affects the yellowing and sulforaphane content of fresh cut broccoli.The effects of different storage temperatures on yellowing and SFN content of fresh cut broccoli were studied.The results showed that the L^*and b^*values of fresh cut broccoli increased,while the greenness(-a^*)and H value decreased,accompanied by the decrease of total chlorophyll and SFN content.Higher storage temperature accelerated the yellowing of broccoli and the loss of chlorophyll and SFN.Lower temperature such as 0?and 4?could effectively alleviate these phenomena.In addition,the results of correlation and regression analysis showed that the color parameters L^*,a^*,b^*were significantly negatively correlated with the total chlorophyll content and SFN content in broccoli,while the H value was significantly positively correlated with the two components.2.Melatonin immersion affects the quality of fresh-cut broccoli(Brassica oleracea L.)during cold storage.The results indicated that 100?M melatonin treatment inhibited the increase of L*and b*value,and retained higher hue angle,total chlorophyll content and fresh weight during storage.100?M melatonin treatment obviously increased antioxidant contents including ascorbic acid,total phenols and flavonoids,and enhanced antioxidant activity of florets.Individual phenolic compounds including epicatechin,rutin and quercetin were positively influenced by melatonin treatment.Superoxide dismutase(SOD),ascorbate peroxidase(APX)and catalase(CAT)activities were obviously enhanced by 100?M melatonin treatment whereas peroxidase(POD)activity was significantly reduced.Moreover,florets treated with melatonin exhibited lower malondialdehyde(MDA),H₂O₂and O₂^-levels,and melatonin reduced the total aerobic bacteria count at the end of storage.Our research concluded that melatonin treatment could be an effective technique for enhancing antioxidant capacity and improving the quality of fresh-cut broccoli during cold storage.3.Melatonin treatment affects the glucoraphanin-SFN system in postharvest fresh-cut broccoli(Brassica oleracea L.).The results showed that florets treated with 100?M melatonin exhibited higher contents of total glucosinolates,glucoraphanin and SFN.Expressions of glucoraphanin biosynthesis genes including Elong,CYP83A1,MYB28,UGT74B1 and FMOGS-OX1 were up-regulated while AOP2 was obviously decreased by melatonin treatment,leading to a higher glucoraphanin accumulation.In addition,application of melatonin enhanced the myrosinase activity and the expression level of MYO,benefiting the formation of SFN.This study demonstrates that melatonin treatment positively affected the glucoraphanin-SFN system in postharvest fresh-cut broccoli.4.Synergistic effects of high pressure and microwave processing in enhancing SFN production of broccoli florets.The optimum condition of HPP was3 min treatment at 400 MPa,which effectively inactivated the microorganism,destroyed the surface structure,and enhanced the antioxidant activity and SFN production of florets.MW treatment increased the greenness(-a^*)and antioxidant activity,while heating at 462 W for 20 s resulted in the highest SFN content in control florets.The loss of antioxidant activity and the increase of yellowness(b^*)was observed in 400 MPa treated florets after several MW treatments.Both 400 MPa and MW treatment promoted the exudation of glucoraphanin,and synergistically activate myrosinase,thus their combination further led to higher yield of SFN after hydrolysis for 10 min or chewing for 30 s.The results indicate the combination of HPP and MW was of significant benefit for the enrichment of SFN in florets and the effective consumption of broccoli as a functional food.5.SFN attenuates 5-fluorouracil induced intestinal injury in mice.5-Fluorouracil(5-Fu)is a chemotherapy drug and can cause intestinal mucositis.In this study,the effects of SFN treatment at low(2 mg/kg)and high(20 mg/kg)doses on 5-Fu induced intestinal injury were evaluated.Compared with 5-Fu group,the severity of intestinal injury was significantly attenuated by SFN treatments,which alleviated the weight loss,repaired the disruption of epithelium structure in jejunum and colon,reduced the intestinal inflammation and healed intestinal permeability.However,SFN administration had no significant effect on the short-chain fatty acids(SCFAs)concentration which was reduced by 5-Fu treatment.Meanwhile,SFN treatments especially at high dose,significantly up-regulated the gene expression related to antioxidant defense(Nrf2&HO-1)and tight junction(Claudin-1)in jejunum,while decreasing the expression of inflammation related genes(NF?B&iNOS)compared to 5-Fu group.Therefore,SFN treatment may be a promising strategy to reduce intestinal injury in chemotherapy.