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Cytoprotective effects of methanolic extracts from leaves of different Globularia spp. in human hepatocellular carcinoma Hep G2 cells with induced hyperglycemia

Globularia alypum L. is a Mediterranean medicinal plant, whose leaves are frequently used in the treatment of diabetes by people from North African countries. Its extracts were previously shown to possess antihyperglycemic activity in vivo as well as antioxidant activity both in vitro and in vivo. Other species from the same genus were recently reported to exhibit antioxidant properties as well. In diabetes mellitus, liver cells, which are largely involved in the regulation of constant blood glucose levels, can be especially susceptible to increased oxidative damage as a result of the hyperglycemia-induced increase of free radical production and/or decrease of antioxidative defense mechanisms. The aim of the present study was to establish the effects of methanolic extracts (0, 5 mg/mL and 1, 0 mg/mL) obtained by ultrasound-assisted extraction of leaves from G. alypum and three related species (G. cordifolia L., G. meridionalis (Podp.) O.Schwarz and G. punctata Lapeyr.) on cell viability of human hepatocellular carcinoma Hep G2 cells in hyperglycemic conditions using the lactate dehydrogenase (LDH) and the 3-(4, 5- dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) cell viability assay. Contents of secondary metabolites, i.e. total phenolics, flavonoids, condensed tannins and iridoids, were evaluated spectrophotometrically, while the major extract components were identified using LC-PDA- ESI-MSn. All samples displayed an inverse effect on the hyperglycemia-induced cytotoxicity in Hep G2 cells in the LDH test. The observed effect was correlated with the established flavonoid (r = 0.88, P = 0.004) and total phenolic content (r = 0.75, P = 0.031). In both used cell viability assays, the greatest cytoprotective effect was shown by extracts from G. punctata, which were especially rich in flavonoids (e.g. 6- hydroxyluteolin 7-O-glucoside, 6-hydroxyluteolin 7-O-sophoroside, 6-hydroxyluteolin 7-O-(6’’’-O- caffeoyl)-sophoroside, 6-hydroxyluteolin 7-O- (6’’’-O-p-coumaroyl)-sophoroside) and iridoids (e.g. asperuloside, besperuloside, globularin). The observed cytoprotective effects might partially explain the use of G. alypum as an antidiabetic agent. With this in mind, related species of the genus Globularia might also have beneficial effects in diabetes treatment, possibly due to some similarities in their phytochemical composition.

cell viability, diabetes mellitus, Globularia, Hep G2

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