Glucosinolates and isothiocyanates from broccoli seed extract suppress protein glycation and carbonylation
Background: Glucosinolates from brassica plants are hydrolyzed by internal or salivary myrosinase to produce isothiocyanates. Glucoraphanin, a major glucosinolate in broccoli, is hydrolyzed to sulforaphane (SFN), which exhibits antitumor and detoxification activities. Regarding the influence of broccoli and its constituents on the skin, a few studies have reported anti-inflammatory and antioxidant effects. Recently, advanced glycation end products (AGEs) and carbonyl proteins have been reported to accelerate skin aging.
Objective: We evaluated the effects of broccoli seed extract (BSE) and glucosinolates on protein glycation and carbonylation in vitro.
Methods: To evaluate the effects of BSE and its constituents, protein glycation and carbonylation were induced by mixing fructose with bovine serum albumin (BSA) and then measuring production of AGEs, fructosamine, and carbonyl proteins (CP). Production of CP after mixing fatty acids with BSA was also assessed. Furthermore, the effect of BSE and its constituents on CP production by human fibroblasts (TIG103) was examined.
Results: BSE suppressed the production of AGEs, fructosamine, and CP after mixing fructose and BSA. BSE also suppressed production of CP when oxidized linoleic acid was mixed with BSA. Isothiocyanates, including SFN and iberin, suppressed fructose-based CP production, but SFN had no effect on CP production stimulated by oxidized linoleic acid. In contrast, glucosinolates from BSE did not suppress fructose-based CP production, but suppressed CP production due to oxidized linoleic acid. Among the glucosinolates in BSE, glucoberteroin showed the strongest suppression of CP production. CP production in fibroblasts was also suppressed by glucosinolates, including glucoiberin and glucoberteroin.
Conclusions: BSE demonstrated anti-glycation and anti-carbonylation effects on protein reactions with fructose and oxidized fatty acids. Isothiocyanates suppressed protein carbonylation induced by fructose, but not those induced by oxidized lipids. On the other hand, glucosinolates (precursors of isothiocyanates) did not suppress protein carbonylation induced by fructose, but suppressed carbonylation due to oxidized lipids. Moreover, glucoberteroin and glucoiberin suppressed CP production in a cell-based assay. These results suggest that glucosinolates in BSE could suppress protein carbonylation leading to aging of the skin.
Keywords: Broccoli; glucosinolate; sulforaphane; carbonylation; glycation; glucoberteroin; glucoiberin
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