Chemical characterization and antioxidative activity of four 3-hydroxyl-3-methylglutaroyl (HMG)-substituted flavonoid glycosides from Graptopetalum paraguayense E. Walther

Abstract

BackgroundGraptopetalum paraguayense E. Walther is a popular traditional Chinese herb and possesses several health benefits. In earlier studies, we demonstrated that G. paraguayense showed no genotoxicity and showed several biological activities. However, the constituents of G. paraguayense have not been studied yet. In this present study, we isolated and identified the constituents of the leaves of G. paraguayense E. Walther.ResultsA total of seven flavonoid compounds were isolated from the methanolic extract of G. paraguayense. The four major compounds isolated were flavonoid glucoside derivatives of quercetin (1, 3) and kampferol (2, 4), each presenting a 3-hydroxyl-3-methylglutaroyl (HMG) substituent; compounds 3 and 4—the 2´´-acetyl derivatives of 1 and 2, respectively—are novel compounds isolated from nature for the first time. High-performance liquid chromatography for the quantitative analyses of the four major HMG-substituted flavonoid glycosides in G. paraguayense E. Walther were accomplished to acquire the high yields of 1–4 in the methanolic extract (4.8, 5.7, 4.3, and 2.5 mg/g, respectively). Furthermore, the antioxidant activities, including radical-scavenging, reducing power and lipid peroxidation inhibitory effects of these isolated flavonoids were also evaluated. All seven of the isolated flavonoid compounds possessed antioxdative activity.ConclusionsIn this study of the constituents of the leaves of G. paraguayense E. Walther, we isolated four major components from its methanolic extract and determined their structures to be (acetylated) HMG-substituted flavonol glycosides, which are rare in nature. All seven of the isolated compounds possessed antioxdative activity, and those flavonoid compounds may be responsible for the functional ingredients in G. paraguayense. Further investigation of their bioactivities or pharmacological activities will be continued.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-015-0088-4) contains supplementary material, which is available to authorized users.

Anti-Herpes Simplex virus and antibacterial activities of Graptopetalum paraguayense E. Walther leaf extract: a pilot study

“…Concerning the possible mechanism of action of the GP extract, based on our data we could hypothesize that most probably it does not target the same cellular structures as b-lactam antibiotics [40] because there was no difference in the activity of the GP extract against the methicillin sensitive and methicillin resistant S. aureus tested in the present study. The in vitro antibacterial and anti-biofilm activities found in our experiments as well as the proven antioxidant effect [15] of G. paraguayense may be attributed to the presence of secondary metabolites belonging to various chemical classes present in the GP extract [33].…”

“…Little data exist for the GP chemical composition that could be associated with its bio-medical benefits. Seven flavonoid glucoside derivatives of quercetin and kaempferol were isolated from GP methanol extract by Liu et al [33]. To evaluate the anti-oxidative activities of water (GWE), 50% ethanol (GE50), and 95% ethanol (GE95) extracts of GP, the total phenol and anthocyanin contents were analyzed by Chung et al [15].…”

Antioxidant Activity of Graptopetalum paraguayense E. Walther Leaf Extract Counteracts Oxidative Stress Induced by Ethanol and Carbon Tetrachloride Co-Induced Hepatotoxicity in Rats

“…G. paraguayense E. Walther mainly contained flavonoids that were identified in our study (Figure 4). It has also been reported that G. paraguayense E. Walther contains various antioxidants, such as gallic acid, quercetin, genistin, and daidzin [16,17]. The protective effects of GE50 may be attributed to the presence of polyphenolic compounds such as gallic acid, flavone, genistin, daidzin, and quercetin.…”

“…Determine the polyphenolic compounds in GE50 extracts, HPLC analysis was performed in accordance with our previously described method with modifications [16,27]. GE50 was dissolved in 50% ethanol, filtered, and analyzed by HPLC.…”

“…It has also demonstrated dose-dependent ACE inhibitory activity, and the kinetics of ACE inhibition reveal that the G. paraguayense extracts are mixed-type inhibitors [13]. Our previous study also demonstrated that the leaf extracts of G. paraguayense are safe and have a potential antioxidative activity [14,15,16]. The previous studies have shown that G. paraguayense plays neuroprotective effects of brain injury in ischemic rats [17] and reduces oxidative stress in hypercholesterolemia patients [18].…”