Chemical constituents of gentianaceae XXVIII: flavonoids of Enicostemma hyssopifolium (Willd.) Verd

Molecular Actions of Enicostemma hyssopifolium Whole Plant Extract on HPV18-Infected Human Cervical Cancer (HeLa) Cells

OBJECTIVE

Enicostemma hyssopifolium (E. hyssopifolium) contains several bioactive compounds with anti-cancer activities. This study was performed to investigate the molecular effects of E. hyssopifolium on HPV18-containing HeLa cells.

METHODS

The methanol extract of E. hyssopifolium whole plant was tested for cytotoxicity by MTT assay. A lower and higher dose (80 and 160 μg/mL) to IC50 were analyzed for colonization inhibition (Clonogenic assay), cell cycle arrest (FACS analysis), and induction of apoptosis (AO/EtBr staining fluorescent microscopy and FACS analysis) and DNA fragmentation (comet assay). The HPV 18 E6 gene expression in treated cells was analyzed using RT-PCR and qPCR.

RESULTS

A significant dose-dependent anti-proliferative activity (IC50 - 108.25±2 μg/mL) and inhibition of colony formation cell line were observed using both treatments. Treatment with 80 μg/mL of extract was found to result in a higher percent of cell cycle arrest at G0/G1 and G2M phases with more early apoptosis, while 160 μg/mL resulted in more cell cycle arrest at SUBG0 and S phases with late apoptosis for control. The comet assay also demonstrated a highly significant increase in DNA fragmentation after treatment with 160 μg/mL of extract (tail moments-19.536 ± 17.8), while 80 μg/mL of extract treatment showed non-significant tail moment (8.152 ± 13.0) compared to control (8.038 ± 12.0). The RT-PCR and qPCR results showed a significant reduction in the expression of the HPV18 E6 gene in HeLa cells treated with 160 μg/mL of extract, while 80 μg/mL did not show a significant reduction.

CONCLUSION

The 160 μg/mL methanol extract of E. hyssopifolium demonstrated highly significant anti-cancer molecular effects in HeLa cells.

Digital Database of Absorption Spectra of Diverse Flavonoids Enables Structural Comparisons and Quantitative Evaluations

Flavonoids play diverse roles in plants, comprise a non-negligible fraction of net primary photosynthetic production, and impart beneficial effects in human health from a plant-based diet. Absorption spectroscopy is an essential tool for quantitation of flavonoids isolated from complex plant extracts. The absorption spectra of flavonoids typically consist of two major bands, band I (300-380 nm) and band II (240-295 nm), where the former engenders a yellow color; in some flavonoids the absorption tails to 400-450 nm. The absorption spectra of 177 flavonoids and analogues of natural or synthetic origin have been assembled, including molar absorption coefficients (109 from the literature, 68 measured here). The spectral data are in digital form and can be viewed and accessed at http://www.photochemcad.com. The database enables comparison of the absorption spectral features of 12 distinct types of flavonoids including flavan-3-ols (e.g., catechin, epigallocatechin), flavanones (e.g., hesperidin, naringin), 3-hydroxyflavanones (e.g., taxifolin, silybin), isoflavones (e.g., daidzein, genistein), flavones (e.g., diosmin, luteolin), and flavonols (e.g., fisetin, myricetin). The structural features that give rise to shifts in wavelength and intensity are delineated. The availability of digital absorption spectra for diverse flavonoids facilitates analysis and quantitation of these valuable plant secondary metabolites. Four examples are provided of calculations─multicomponent analysis, solar ultraviolet photoprotection, sun protection factor (SPF), and Förster resonance energy transfer (FRET)─for which the spectra and accompanying molar absorption coefficients are sine qua non.

Immunomodulatory potential of Enicostema axillare (Lam.) A. Raynal, a traditional medicinal plant

ETHNOPHARMACOLOGICAL RELEVANCE

Enicostema axillare (Lam.) A. Raynal., (Gentianaceae) has been used in traditional Indian system of medicine as depurative and for the treatment of psoriasis, intermittent fever and cancer. Ethnobotanical survey conducted in Theni District indicated a high consensus for this plant as blood purifier and to treat dermatopathy and venereal infections. The present study evaluated the immunomodulatory activity of the methanol extract of Enicostema axillare.

MATERIALS AND METHODS

In vivo immunomodulatory activity of Enicostema axillare methanol extract (100 and 200mg/kg b.w) was evaluated by assessing its effect on the total and differential leukocyte count, organ weight, hemaggultinating antibody titer, plaque forming cells, quantitative hemolysis of SRBC and delayed type hypersensitivity. Sheep red blood cells (SRBC, 5×10(8)cells/0.1mL) were used to immunize the animals. In vitro immunomodulatory potential of the extract was studied using peritoneal macrophages by evaluating its effects on NBT reduction, NO production and cytokine release.

RESULTS

The animals treated with Enicostema axillare methanol extract showed a significant (P≤0.05) increase in weight of the thymus and spleen. The total leukocyte and lymphocyte count was increased significantly (P<0.005) by the treatment. There was no significant alteration in neutrophil count. A dose dependent increase in antibody titer value was observed. A decreased response to DTH reaction induced by SRBC was recorded. A potential phagocytic response was seen on treatment with the extracts at 10 and 25μg/mL. The extract inhibited the release of pro-inflammatory cytokines and production of NO significantly in a dose dependent manner.

CONCLUSION

These findings suggested that the methanol extract of Enicostema axillare acted on both humoral and cell mediated immune functions and decreased the release of pro-inflammatory cytokines in the peritoneal macrophages.

Antiulcer and Anti-inflammatory Activity of Aerial Parts Enicostemma littorale Blume

The antiulcer and in vitro anti-inflammatory activities of the aerial parts of Enicostemma littorale against aspirin, ethanol, and pyloric ligation-induced ulcers in rats and bovine serum albumin denaturation were studied. The extract (200 mg/kg and 400 mg/kg po) was administered to the overnight fasted rats, one hour prior to aspirin / alcohol / pyloric ligation challenge. The ulcer index, tissue GSH levels, and lipid peroxidation levels were estimated in all the models of ulcers and the volume of gastric secretion, acidity, and pH, were estimated in the pyloric ligation model of ulcers. Pretreatment with the extract showed a dose-dependent decrease in the ulcer index (Against Aspirin, ethanol challenge, and pyloric ligation. The prior administration of the extract also reduced the total acidity, free acidity, and volume of gastric secretion, and elevated the gastric pH. In addition, it was also observed that the extract inhibited the serum albumin denaturation in a dose-dependent manner. It may be concluded that the methanolic extract possesses antiulcer activity, and the anti-inflammatory activity of the extract may be attributed to the antioxidant potential, as reported earlier.

Hypoglycemic activity of C-glycosyl flavonoid from Enicostemma hyssopifolium

CONTEXT

Enicostemma hyssopifolium Verdoon (Gentianaceae) has been documented for various therapeutic effects in traditional systems of medicine; the hypoglycemic and hypolipidemic activities are also well reported.

OBJECTIVE

Bioactivity guided fractionation of methanol extract of E. hyssopifolium to test the hypothesis that E. hyssopifolium and its constituents influence cells and systemic glucose homeostasis.

MATERIALS AND METHODS

Derived fraction and isolated compounds were studied for (1) aldose reductase (AR) inhibition, (2) α-glucosidase inhibition, (3) effect on gluconeogenesis in rat hepatoma, (4) cytoprotection against streptozotocin (STZ)-induced toxicity on RINm5F cells, (5) normalization of glycemic control in acute hyperglycemic rat model, and (6) insulin-releasing effect both in vitro and in vivo.

RESULTS

The results indicated that E. hyssopifolium can modify the glucose homeostasis at the cellular level. Two bioactive constituents were identified. Swertisin was found to inhibit AR (IC(50) 1.23 μg/mL) and α-glucosidase (IC(50) 1.89 μg/mL). It also possessed a significant cytoprotective action of RINm5F cell line against toxicant STZ. Swertiamarin was found to have hepatic gluconeogenesis inhibiting and insulin-releasing effect on rat hepatoma and RINm5F cells, respectively. The results of the in vivo study showed that swertiamarin, unlike the in vitro effect, produced no significant raise of insulin secretion. Swertisin normalized the serum glucose 60 min after high dose of glucose (2 g/kg, i.p.) in rats.

DISCUSSION AND CONCLUSION

These findings demonstrate that the fraction derived from the aerial part of E. hyssopifolium achieve normoglycemic status in hyperglycemic conditions via various mechanisms. The constituents swertiamarin and swertisin are responsible for bioactivity.

The biochemistry and medical significance of the flavonoids

Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.

Effect of chronic treatment with Enicostemma littorale in non-insulin-dependent diabetic (NIDDM) rats

We have studied the effect of aqueous extract of Enicostemma. littorale (2 g/kg p.o.) daily for 6 weeks in neonatal non-insulin-dependent diabetes mellitus (NIDDM) rats. To induce NIDDM a single dose injection of STZ (70 mg/kg; i.p.) was given to the 5-day-old pups. After 3 months of STZ injection when animals were confirmed as diabetic, E. littorale was administered for 6 weeks. Fasting and fed glucose and insulin levels in NIDDM were significantly (P<0.05) higher than control rats and they were significantly decreased by the treatment with E. littorale. Results of the oral glucose tolerance test (OGTT) showed a significant (P<0.05) decrease in both AUC(glucose) and AUC(insulin) values in NIDDM treated group. Insulin sensitivity (K(ITT)) index of NIDDM control was significantly lower as compared with Wistar control and this was significantly (P<0.05) increased after treatment with E. littorale. Treatment with E. littorale also decreased the elevated cholesterol, triglyceride and creatinine levels observed in NIDDM rats. Our data suggest that aqueous extract of E. littorale is a potent herbal antidiabetic. It produces an increase in insulin sensitivity, normalizes dyslipidaemia and provides nephroprotection in diabetic rats.

A new flavone C-glycoside and antiplatelet and vasorelaxing flavones from Gentiana arisanensis

A new flavone C-glycoside, isovitexin 6"-O-glucoside (1), and three known flavonoids, quercetin, isovitexin, and luteolin-7-O-beta-D-glucoside, have been further isolated from the whole plant of Gentiana arisanensis Hayata. The new compound was characterized by spectral methods and chemical reactions. The antiplatelet effects of isovitexin 6"-O-glucoside (1), isoorientin (2), 2 peracetate (3), isovitexin (4), luteolin 7-O-beta-D-glucoside (5), luteolin (6), isoorientin 6"-O-glucoside (7), and 7 peracetate (8) were studied using washed rabbit platelets. Of the compounds tested, 6 showed potent antiplatelet effects on arachidonic acid (AA)-induced platelet aggregation (IC50 = 43.5 microM). The effect of 2, 5, and 6 on the contraction of rat thoracic aorta was also studied. Compound 6 depressed markedly the contraction induced by Ca2+ (1.9 mM) in high-K+ (80 mM) medium, with an IC50 of about 156 microM and also inhibited noradrenaline (3 microM)-induced phasic and tonic contractions, with an IC50 of about 68 and 72 microM, respectively.