Pterostilbene improves glycaemic control in rats fed an obesogenic diet: involvement of skeletal muscle and liver.

This study aims to determine whether pterostilbene improves glycaemic control in rats showing insulin resistance induced by an obesogenic diet. Rats were divided into 3 groups: the control group and two groups treated with either 15 mg kg(-1) d(-1) (PT15) or 30 mg kg(-1) d(-1) of pterostilbene (PT30). HOMA-IR was decreased in both pterostilbene-treated groups, but this reduction was greater in the PT15 group (-45% and -22% respectively vs. the control group). The improvement of glycaemic control was not due to a delipidating effect of pterostilbene on skeletal muscle. In contrast, GLUT4 protein expression was increased (+58% and +52% vs. the control group), suggesting an improved glucose uptake. The phosphorylated-Akt/total Akt ratio was significantly enhanced in the PT30 group (+25%), and therefore a more efficient translocation of GLUT4 is likely. Additionally, in this group the amount of cardiotrophin-1 was significantly increased (+65%). These data suggest that the effect of pterostilbene on Akt is mediated by this cytokine. In the liver, glucokinase activity was significantly increased only in the PT15 group (+34%), and no changes were observed in glucose-6-phosphatase activity. The beneficial effect of pterostilbene on glycaemic control was more evident with the lower dose, probably because in the PT15 group both the muscle and the liver were contributing to this effect, but in the PT30 group only the skeletal muscle was responsible. In conclusion, pterostilbene improves glycaemic control in rats showing insulin resistance induced by an obesogenic diet. An increase in hepatic glucokinase activity, as well as in skeletal muscle glucose uptake, seems to be involved in the anti-diabetic effect of this phenolic compound.

Delayed growth of glioma by Scutellaria flavonoids involve inhibition of Akt, GSK-3 and NF-κB signaling.

Plants of the genus Scutellaria constitute one of the common components of Eastern as well as traditional American medicine against various human diseases, including cancer. In this study, we examined the in vivo anti-glioma activity of a leaf extract of Scutellaria ocmulgee (SocL) while also exploring their potential molecular mechanisms of action. Oral administration of SocL extract delayed the growth of F98 glioma in F344 rats, both in intracranial and subcutaneous tumor models. Immunohistochemistry revealed inhibition of Akt, GSK-3α/ß and NF-κB phosphorylation in the subcutaneous tumors following treatment with Scutellaria. The SocL extract as well as the constituent flavonoid wogonin also showed dose- and time-dependent inhibition of Akt, GSK-3α/ß and NF-κB in F98 cell cultures in vitro, as determined by western blot analysis. Pharmacologic inhibitors of PI3K and NF-κB also significantly inhibited the in vitro proliferation of F98 glioma cells, indicating the key role of these signaling molecules in the growth of malignant gliomas. Transfection of F98 cells with constitutively active mutant of AKT (AKT/CA), however, did not significantly reverse Scutellaria-mediated inhibition of proliferation, indicating that Scutellaria flavonoids either directly inhibited Akt kinase activity or acted downstream of Akt. In vitro Akt kinase assay demonstrated that the SocL extract or wogonin could indeed bind to Akt and inhibit its kinase activity. This study provides the first in vivo evidence and mechanistic support for anti-glioma activity of Scutellaria flavonoids and has implications in potential usage of Scutellaria flavonoids in adjuvant therapy for malignant tumors, including gliomas.

Effect of natural analogues of trans-resveratrol on cytochromes P4501A2 and 2E1 catalytic activities.

The aim was to assess the inhibitory effect of a series of naturally occurring trans-resveratrol analogues on cytochromes P450, namely CYP1A2 and CYP2E1, in vitro in order to analyse any structure-activity relationships. 3,5-Dimethoxy-4'-hydroxy-trans-stilbene (pterostilbene), 3,4',5-trimethoxy-trans-stilbene (TMS), 3,4'-dihydroxy-5-methoxy-trans-stilbene (3,4'-DH-5-MS) and 3,5-dihydroxy-4'-methoxy-trans-stilbene (3,5-DH-4'-MS) inhibited the activity of CYP1A2, with K(i) = 0.39, 0.79, 0.94 and 1.04 microM, respectively. Piceatannol (3,3',4,5'-tetrahydroxy-trans-stilbene) was the least potent inhibitor of CYP1A2 with a K(i) = 9.67 microM. Piceatannol and TMS in the concentration range 1-100 microM did not inhibit CYP2E1 activity. The activity of this enzyme likewise was not significantly influenced by pterostilbene and 3,5-DH-4'-MS with IC(50) > 100 microM, whereas 3,4'-DH-5-MS appeared to be a moderately potent, competitive inhibitor of CYP2E1 (K(i) = 42.6 microM). Structure-activity relationship analysis leads to the conclusion that the substitution of hydroxy groups of resveratrol with methoxy groups increases the inhibition of CYP1A2, yet the number and position of methylation are not essential. However, the 4'-hydroxy group in trans-resveratrol and its analogues may play an important role in the interaction with a binding site of CYP2E1.

Phytotoxic lignans of Leucophyllum frutescens.

Bioassay-guided fractionation of the hexane:ethyl acetate (1:1) extract of the leaves of Leucophyllum frutescens (Berl.) I.M.Johnst (Scrophulariaceae) led to the isolation of its phytotoxic constituents diayangambin (1), epiyangambin (2), diasesartemin (3) and epiashantin (4). Phytotoxicity was demonstrated as inhibition of seed germination of Agrostis stolonifera cv. penncross (Poaceae) and inhibition of development of Lactuca sativa L. (Asteraceae) seedlings in a microassay using 24-well plates. Compound 1 was the most phytotoxic to L. sativa, showing strong inhibitory activity at 110 microM. Compound 1 was more active than 2 and 3 in inhibiting the growth of A. stolonifera with I(50) values of 160, 670 and 930 microM, respectively. At a concentration of 500 microM, these compounds inhibited all phases of onion root cell division. This is the first demonstration of antimitotic activity of these furofuran lignans, and the first report of their isolation from this species.

Thiol-dependent degradation of protoporphyrin IX by plant peroxidases.

Protoporphyrin IX (PP) is the last porphyrin intermediate in common between heme and chlorophyll biosynthesis. This pigment normally does not accumulate in plants because its highly photodynamic nature makes it toxic. While the steps leading to heme and chlorophylls are well characterized, relatively little is known of the metabolic fate of excess PP in plants. We have discovered that plant peroxidases can rapidly degrade this pigment in the presence of thiol-containing substrates such as glutathione and cysteine. This thiol-dependent degradation of PP by horseradish peroxidase consumes oxygen and is inhibited by ascorbic acid.

Effects of Fusarium mycotoxins on levels of serotonin, melatonin, and 5-hydroxytryptophan in pineal cell cultures.

Analysis of melatonin (MEL) in pineal cell cultures by enzyme linked immunosorbent assay showed its concentration was increased by fusaric acid (FA), a mycotoxin produced by Fusarium species and associated with toxic duck and ostrich feeds. Subsequent cell culture studies demonstrated the precursors of MEL, 5-hydroxytryptophan (5HTP) and serotonin (5HT), were also affected by FA as well as other Fusarium mycotoxins. Herein we describe a technique for the analysis of 5HTP and 5HT in pineal cell cultures using HPLC with electrochemical detection (EC), and report on the effects of FA alone and in combination with fumonisin B1 (FB1) and deoxynivalenol (DON) on the levels of these MEL precursors.

A new photosystem II electron transfer inhibitor from Sorghum bicolor.

Our study of the mechanism(s) by which sorgoleone (1) acts as a photosystem II (PS II) inhibitor led to the isolation of a new benzoquinone derivative, 2-hydroxy-5-ethoxy-3-[(Z,Z)-8',11', 14'-pentadecatriene]-rho-benzoquinone (2), from the root exudate of sorghum. The structure of 2, which is being given the name 5-ethoxy-sorgoleone, was determined by spectroscopic means. A methoxy derivative (3) of 1 was also prepared. Both 2 and 3 caused a reduction in oxygen evolution by thylakoid membranes and induced variable chlorophyll fluorescence. These compounds, however, were less active inhibitors of PS II than 1.

Fusaric acid increases melatonin levels in the weanling rat and in pineal cell cultures.

Fusaric acid (FA) is produced by several Fusarium species that commonly infect cereal grains and other agricultural commodities. FA in the feed of nursing dams is lactationally transferred to the suckling offspring and alters serotonin (5-hydroxytryptamine, 5HT) in the pineal gland of the neonate rat. 5HT is involved in melatonin (MEL) production by the pineal gland. MEL is a hormone important in reproduction and seasonality in animals. Therefore, the effects of FA on MEL in the serum and pineal gland of male and female 21-d-old weanling rats from dams on an FA diet were studied. MEL was measured by enzyme-linked immunosorbent assay (ELISA), which was standardized for directly measuring MEL in rat serum and pineal homogenates. At 200 ppm in the diet of nursing dams, FA increased serum MEL in both sexes. Results obtained from ELISA were supported by high-performance liquid chromatography (HPLC) analysis with fluorescence detection. MEL analysis of the pineal gland homogenates by ELISA and HPLC supported observations in the serum. Analogously, in pineal cell monolayer cultures, FA at 1 microM and 100 microM concentrations increased MEL in a dose-dependent manner as compared to the control cells. This is the first report that FA increases MEL in vivo and in vitro and suggests that FA contamination of diets may affect mechanisms involving MEL synthesis.

Lactational passage of fusaric acid from the feed of nursing dams to the neonate rat and effects on pineal neurochemistry in the F1 and F2 generations at weaning.

Fusaric acid is produced by several species of Fusarium and is found in corn, corn-based foods and feeds, wheat, barley, and other cereal grains. Given parenterally to rats, the mycotoxin affects neurochemical parameters in the pineal gland associated with growth and maturation. Since little information exists concerning the dietary effects of fusaric acid, the mycotoxin was mixed with feed at 10, 75, and 200 ppm and fed ad libitum to pregnant rats (F0 dams) from d 11-12 of gestation, through parturition and weaning (F1 generation). On d 4 postpartum, F1 pups were culled to 9-10 pups/litter; the stomach colostrum was collected from the culls and analyzed for fusaric acid. The mycotoxin in the colostrum (ng fusaric acid/100 mg colostrum) was directly related to the amount consumed by the nursing dams (i.e., 200 ppm pups, 3547 ng; 75 ppm pups, 1449 ng; 10 ppm pups, 80 ng; controls pups, 18 ng). All other animals survived, and appeared normal, healthy, and in good pelage. F0 dam feed consumption and dam and pup weights were not statistically different, but there was an inverse relation between pup average weight gain and amount of fusaric acid in the diets (i.e., weight gains: control pup > 10 ppm pup > 75 ppm pups > 200 ppm pups). At weaning, the F1 pups were randomly assigned to two groups per treatment: one group (F1A) for reproduction and fusaric acid effects on the F2 generation, and another group (F1B) for neurochemical comparisons. The F1A rats were maintained on their respective diets to age 13-14 wk; animals were bred (i.e., control males x control females, 10 ppm x 10 ppm, etc.) and the F1A dams and F2 pups were monitored as already described. Weight gains and fusaric acid in stomach colostrum from the F2-culls were analogous to the F1 generation. On d 5-6 and 7-8 postpartum, using litter weight gains as an indication of milk production in the F1A dams (controls vs. 200 ppm), the controls gained 32.5% (p < .01) and 13.3% (p < .02), respectively, more than 200 ppm F2 pups. At weaning, no differences were observed in neurochemicals in the pineal gland for the F1 generation. However, in the F2 200 ppm male and female weanlings, fusaric acid decreased pineal serotonin (males, p < or = .001; females, p < or = .15) and tyrosine (males, p < or = .04; females, p < or = .07). The results indicate fusaric acid in diets at < or = 0.3 ppm (i.e., background control diet) lactationally passes from nursing dams to the neonate; in weanlings, at 200 ppm, fusaric acid decreases pineal serotonin and tyrosine. The data also suggest limited neonate weight gains may be related to either decreased milk production in dams or mycotoxin effects on the neonate. This is the first report of fusaric acid's lactational passage from the feed of nursing dams to neonates and the oral suppression of pineal serotonin and tyrosine in offspring.

New lignans from Anogeissus acuminata with HIV-1 reverse transcriptase inhibitory activity.

Anolignan A [1] and anolignan B [3] are new dibenzylbutadiene lignans isolated from Anogeissus acuminata. Compounds 1 and 3 were identified as the active HIV-1 reverse transcriptase (RT) inhibitory constituents of this plant obtained by bioassay-guided fractionation. Compound 3, which was very weakly active when tested alone, showed high activity when combined with 1. The activity of 1 was likewise enhanced in the presence of 3. A concave isobole obtained from a plot of data derived from assays with 1 and 3 in combination indicated their synergistic effects. Another new lignan, anolignan C [5], and a known lignan, (-)-secoisolariciresinol [10], were also isolated from this plant. Compounds 5 and 10 did not have activity against HIV-1 RT. Compounds 1, 3 and 5 were either weakly cytotoxic or noncytotoxic when tested in various cancer cell lines. The structures of 1-5 and 10 were established by spectroscopic methods, especially by 1D and 2D nmr experiments.

Sesquiterpene lactones and other constituents from a cytotoxic extract of Michelia floribunda.

The pentane and CHCl3 fractions of a crude extract of Michelia floribunda exhibited cytotoxic activity when tested in KB and P388 tumor cell cultures. Repeated chromatography led to the isolation of three cytotoxic sesquiterpene lactones (costunolide, parthenolide, and santamarine) and a cytotoxic isoquinoline alkaloid (liriodenine). Inactive sesquiterpene lactones obtained during the course of this study included dihydroparthenolide and two new glucosides of dihydrotamaulipin A and dihydroreynosin (1 and 2). The structures of these new compounds were determined through interpretation of their spectroscopic data including 2D-NMR spectroscopy. Syringin was also isolated from the extract.