The coumarin osthol attenuates the binding of thyrotropin-releasing hormone in rat pituitary GH4C1 cells.

The influence of two plant coumarins, osthol and xanthotoxin, on intracellular Ca2+ ([Ca2+]i) transients evoked by TRH were studied in clonal rat pituitary GH4C1 cells. Osthol, but not xanthotoxin, decreased the TRH-induced transient increase in [Ca2+]i in Fluo-3 loaded cells incubated in Ca(2+)-free buffer. Binding experiments with [3H]TRH showed that osthol decreased the binding of TRH to its receptor, whereas the affinity of the receptor for TRH increased. This resulted in a decreased TRH-evoked production of IP3 in cells treated with osthol, and a decreased mobilization of sequestered calcium. Osthol did not inhibit the release of calcium evoked by exogenous IP3 in permeabilized cells. Furthermore, osthol decreased the uptake of 45Ca2+ in response to high K+. Xanthotoxin had no effects in these experiments. The results show that osthol modulates TRH-evoked responses by interacting with the TRH receptor.

Vasorelaxing effect of coumarins from Cnidium monnieri on rabbit corpus cavernosum.

Bioassay-directed fractionation led to the identification of four known coumarins, osthole (1), imperatorin (2), xanthotoxin (3), and isopimpinellin (4), from the ethanolic extract of the fruit of Cnidium monnieri (L.) Cusson. In phenylephrine (PE)-precontracted endothelium-intact rabbit corpus cavernosum, all four coumarins exhibited relaxing effect with the IC50 values for compounds 1, 2, 3, and 4 determined to be 2.14 +/- 0.73, 0.85 +/- 0.16, 1.24 +/- 0.45, and 18.4 +/- 8.10 microM, respectively. The four compounds were identified by comparison of their physical data (EIMS, 1H- and 13C-NMR) with those from published reports.

The effect of tetrandrine and extracts of Centella asiatica on acute radiation dermatitis in rats.

Radiation injury to the skin is one of the major limiting factors in radiotherapy. We designed this study using Sprague-Dawley rats to evaluate the reduction in skin injury achieved using natural products from plant extracts as protection. The acute skin reaction in tetrandrine- and Madecassol-treated animals appeared earlier, but was significantly less severe, than in the control group. The peak skin reactions in the tetrandrine group were less serious than those of the control group at three different radiation doses. At a high dose irradiation, the healing effect of tetrandrine is better than Madecassol and vaseline. The histologic findings indicate that tetrandrine and Madecassol are able to reduce acute radiation reactions by their anti-inflammatory activity.

Insulin-releasing and insulin-like activity of the traditional anti-diabetic plant Coriandrum sativum (coriander).

Coriandrum sativum (coriander) has been documented as a traditional treatment of diabetes. In the present study, coriander incorporated into the diet (62.5 g/kg) and drinking water (2.5 g/l, prepared by 15 min decoction) reduced hyperglycaemia of streptozotocin-diabetic mice. An aqueous extract of coriander (1 mg/ml) increased 2-deoxyglucose transport (1.6-fold), glucose oxidation (1.4-fold) and incorporation of glucose into glycogen (1.7-fold) of isolated murine abdominal muscle comparable with 10(-8) M-insulin. In acute 20 min tests, 0.25-10 mg/ml aqueous extract of coriander evoked a stepwise 1.3-5.7-fold stimulation of insulin secretion from a clonal B-cell line. This effect was abolished by 0.5 mM-diazoxide and prior exposure to extract did not alter subsequent stimulation of insulin secretion by 10 mM-L-alanine, thereby negating an effect due to detrimental cell damage. The effect of extract was potentiated by 16.7 mM-glucose and 10 mM-L-alanine but not by 1 mM-3-isobutyl-1-methylxanthine. Insulin secretion by hyperpolarized B-cells (16.7 mM-glucose, 25 mM-KCl) was further enhanced by the presence of extract. Activity of the extract was found to be heat stable, acetone soluble and unaltered by overnight exposure to acid (0.1 M-HCl) or dialysis to remove components with molecular mass < 2000 Da. Activity was reduced by overnight exposure to alkali (0.1 M-NaOH). Sequential extraction with solvents revealed insulin-releasing activity in hexane and water fractions indicating a possible cumulative effect of more than one extract constituent. These results demonstrate the presence of antihyperglycaemic, insulin-releasing and insulin-like activity in Coriandrum sativum.

Effect of parsley (Petroselinum crispum) on the skin of STZ induced diabetic rats.

Parsley (Petroselinum crispum) is one of the medicinal herbs used by diabetics in Turkey and it has been reported to reduce blood glucose. The purpose of this study therefore was to investigate the effect of feeding parsley on diabetes induced impairments in rat skins. Uncontrolled induced diabetes caused significant increases in nonenzymatic glycosylation of skin proteins, lipid peroxidation and blood glucose. Administration of parsley extract did not inhibit these effects except for the increase in blood glucose. SDS-polyacrylamide gel electrophoresis revealed no significant differences in any protein bands between any of the groups.

[Minor Bupleurum decoction in the treatment of viral myocarditis models].

A myocarditis model of Balb/c mice established by means of coxsackie virus type B3 was treated with the Minor Bupleurum Decoction. The results indicate that the decoction can regulate T lymphocyte subsets, influence anti-cardiac antibody production, help the organism to get clear of viruses, and thus plays an important role in treating viral myocarditis.