Composition, Efficacy, and Safety of Spinach Extracts

Abstract

Spinach leaves, containing several active components, including flavonoids, exhibit antioxidative, antiproliferative, and antiinflammatory properties in biological systems. Spinach extracts have been demonstrated to exert numerous beneficial effects, such as chemo- and central nervous system protection and anticancer and antiaging functions. In this review article, we present a compilation of data generated in our laboratories and those of other investigators describing the chemical composition of spinach, its beneficial effects, relative safety information, and its recommended inclusion in the human diet. A powerful, water-soluble, natural antioxidant mixture (NAO), which specifically inhibits the lipoxygenase enzyme, was isolated from spinach leaves. The antioxidative activity of NAO has been compared to that of other known antioxidants and found to be superior in vitro and in vivo to that of green tea, N-acetylcysteine (NAC), butylated hydroxytoluene (BHT), and vitamin E. NAO has been tested for safety and is well tolerated in several species, such as mouse, rat, and rabbit. NAO has been found to be nonmutagenic and has shown promising anticarcinogenic effects in a few experimental models, such as skin and prostate cancer; it has not shown any target-organ toxicity or side effects. The current review provides epidemiological and preclinical data supporting the efficacy of extracts of spinach and the safety of its consumption.

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“…Freshly cut spinach leaves contain approximately 1,000 mg of total flavonoids per kilogram. The possible presence of flavonoid-like compounds in spinach was first reported in 1943 but nearly 20 yr elapsed before the structure of the flavonol isolated from spinach leaves was established as patuletin and the presence of spinacetin was confirmed [11]. In addition, the existence of several flavonol glycosides in a methanolic extract of spinach leaves was reported.…”

“…In addition, the existence of several flavonol glycosides in a methanolic extract of spinach leaves was reported. The occurrence of at least 10 flavonoid glycosides has now been reported in spinach [11]. These are glucuronides and acylated di-and triglycosides of methylated and methylene dioxide derivatives of 6-oxygenated flavonols [11].…”

“…The occurrence of at least 10 flavonoid glycosides has now been reported in spinach [11]. These are glucuronides and acylated di-and triglycosides of methylated and methylene dioxide derivatives of 6-oxygenated flavonols [11]. Glucuronides are more water-soluble than glycosides and acylated compounds that remain in the tissue after cooking in boiling water.…”

Unique natural antioxidants (NAOs) and derived purified components inhibit cell cycle progression by downregulation of ppRb and E2F in human PC3 prostate cancer cells

“…This NAO contains polyphenols, which include phenolic acids (p-coumaric acid derivatives) and the glucuronic acid derivatives of flavonoids [26]. We have shown that NAO has antioxidative [26,27], antiproliferative [28], and antiinflammatory properties [29][30][31][32][33] in various biological systems. Spinach flavonoids have been shown to have strong antimutagenic potential and were found beneficial in a Tg.AC mouse model [33].…”

“…We have shown that NAO has antioxidative [26,27], antiproliferative [28], and antiinflammatory properties [29][30][31][32][33] in various biological systems. Spinach flavonoids have been shown to have strong antimutagenic potential and were found beneficial in a Tg.AC mouse model [33]. Furthermore, spinach NAO has been reported to have a protective effect in various animal models for diseases such as doxorubicin-induced cardiotoxicity [30], skin papilloma [31], and lipopolysaccharide-induced septic shock [29,32].…”