Morphogenetic and diurnal variation of hypericin in some Hypericum species from Turkey during the course of ontogenesis

The genus Hypericum has received considerable interest from scientists, as it is a source of a variety of biologically active compounds including the hypericins. The present study was conducted to determine ontogenetic, morphogenetic and diurnal variation of the total hypericins content in some species of Hypericum growing in Turkey namely, Hypericum aviculariifolium subsp. depilatum var. depilatum (endemic), Hypericum perforatum and Hypericum pruinatum. The Hypericum plants were harvested from wild populations at vegetative, floral budding, full flowering, fresh fruiting and mature fruiting stages four times a day. Plants were dissected into stem, leaf and reproductive tissues, which were dried separately, and subsequently assayed for total hypericin content. The density of dark glands on leaves at full flowering plants was determined for each species. Floral parts had the highest hypericin content in all species tested. But diurnal fluctuation in the hypericin content of whole plant during the course of ontogenesis varied among the species. It reached the highest level at floral budding and tended to increase at night in H. aviculariifolium subsp. depilatum var. depilatum and H. pruinatum, whereas in H. perforatum hypericin content was the highest at full flowering and no diurnal fluctuation was observed. In general, hypericin content of leaves and whole plant was higher in H. aviculariifolium subsp. depilatum var. depilatum whose leaves had more numerous dark glands than those of the two other species.     

Photodynamic therapy of murine fibrosarcoma with topical and systemic administration of Hypericin

The in vivo antitumour activity of the natural photosensitizer hypericin was evaluated. C3H/DiSn mice inoculated with fibrosarcoma G5:1:13 cells were intraperitoneally or intratumourally injected with hypericin (5 mg/kg) and 2 hours later the mice were locally irradiated with laser light (488 nm, 150 mW/cm2, 180 J/cm2) when the tumour reached volume of 40-80 mm3 (approximately 17 days after inoculation). Tumours treated with hypericin alone as well as those irradiated with laser light alone have similar growth rates and none of these tumours regressed spontaneously. The mean tumour volume in hypericin-PDT treated groups was significantly lower in comparison to that found in the control group 3-5 weeks after the therapy. A higher proportion of animals with tumour volume less than 5-fold of the initial volume has been observed in both hypericin-PDT treated groups. Complete response to PDT has been observed for 44.4% of the animals with intraperitoneally administered hypericin and for 33.3% of the animals with intratumourally administered hypericin. Complete remission occurred in treated lesions with 3 mm or less in height. Hypericin-PDT significantly increased survival. However, no statistically significant difference in survival rate of animals has been found between the intratumoural and the intraperitoneal schedule of administration of hypericin.     

贯叶连翘中金丝桃素的合成与积累研究进展

金丝桃素是贯叶连翘的主要药理活性成分。本文概述了金丝桃素的化学与生物合成途径,介绍了金丝桃素在贯叶连翘个体发育过程中的积累以及利用贯叶连翘的细胞和组织培养技术生产与积累金丝桃素的研究进展。最后,指出分子生物学和电子显微镜技术的发展为深入研究金丝桃素的产生和积累提供了有利工具。     

Step-up photophobic response in the ciliate,Stentor coeruleus

The avoidance by Stentor coeruleus of a light trap is caused by a step-up photophobic response. The phobic response invariably consists of a delay of about 200 ms, a stop response, a turn to one side, and resumption of swimming in the new direction. After this the cells enter a refractory period of 1–3 s following a phobic response, during which they will not give a second response. Phobic responses can be elicited by spatial and temporal increases in light intensity. The action spectrum for the step-up photophobic response resembles the absorption spectrum of stentorin, the proposed photoreceptor pigment, and of its chromophore, hypericin.The phobic response is specifically inhibited by the protonophorous uncouplers TPMP⁺ and FCCP but not by the ionophores gramicidin and A23187. Since the uncouplers block light-induced membrane potential changes at the same concentrations, it has been proposed that the primary photoreception causes a light-induced potential change, which in turn, induces a motor response.Abbreviations TPMP⁺ triphenyl methyl phosphonium bromide - FCCP carbonylcyanide p-trifluoromethoxy-phenylhydrazone     

Lipid-mediated preferential localization of hypericin in lipid membranes

Subcellular localization of a photosensitizer is critical to its therapeutic outcome during photodynamic therapy (PDT). We delineated the distribution of hypericin, a new generation photosensitizer, in model membrane systems to identify the operating principles of its subcellular accumulation. Results from fluorescence microscopy indicated preferential incorporation of hypericin in lipid of giant unilamellar vesicles. Monolayer fluorescence measurements further identified cholesterol as the key determinant for the observed selectivity of hypericin. The emission spectra of hypericin in lipid monolayers varied in a lipid-dependent manner and Stoke's shift behavior suggests that hypericin may form closely packed structure with cholesterol. Overall, our data lead to the conclusion that cholesterol is the major origin of the selectivity for hypericin in membrane systems. A hypothetical model depicting the intracellular and intravascular co-transport of hypericin and cholesterol because of their high affinity is presented.     

The antidepressant mechanism of Hypericum perforatum

Clinical data indicate that hydroalcoholic extracts of Hypericum perforatum might be as valuable as conventional antidepressants in mild-to-moderate depression, with fewer side effects. One clinical trial using two extracts with different hyperforin contents indicated it as the main active principle responsible for the antidepressant activity. Behavioural models in rodents confirm the antidepressant-like effect of Hypericum extracts and also of pure hyperforin and hypericin. A hydroalcoholic extract lacking hyperforin also lacks the antidepressant-like effect. According to pharmacokinetic data and binding studies, it appears that the antidepressant effect of Hypericum extract is unlikely be due to an interaction of hypericin with central neurotransmitter receptors. The main in vitro effects of hyperforin (at concentrations of 0.1-1 microM) are non-specific presynaptic effects, resulting in the non-selective inhibition of the uptake of many neurotransmitters, and the interaction with dopamine D1 and opioid receptors. However, it is still not clear whether these mechanisms can be activated in vivo, since after administration of Hypericum extract brain concentrations of hyperforin are well below those active in vitro. In the rat, Hypericum extract might indirectly activate sigma receptors in vivo (through the formation of an unknown metabolite or production of an endogenous ligand), suggesting a new target for its antidepressant effects.     

Detection of hypericins in the "red glands" of Hypericum elodes by ESI-MS/MS

The biologically active naphthodianthrones hypericin and pseudohypericin were detected by electrospray ionization mass spectrometry (ESI-MS/MS) in microsamples from the sepals of Hypericum elodes (Hypericaceae) containing the so-called "red glands", i.e. stipitate glands with red-coloured heads. The occurrence of hypericins in the red glands of H. elodes supports the taxonomic position of the section Elodes within the genus Hypericum and provides evidence that the ability of carrying out the biosynthetic pathway leading to the naphthodianthrone compounds, rather than the absolute amounts produced, should be regarded as a chemical marker of the phylogenetically more advanced sections of genus Hypericum. The biologically active phloroglucinol derivatives hyperforin and adhyperforin, so far found only in H. perforatum, were also detected and evidence for their localization in the sepal secretory canals with large lumen, is given.     

Variation of bioactive secondary metabolites in <Emphasis Type="Italic">Hypericum origanifolium</Emphasis> during its phenological cycle

The genus Hypericum has received considerable interest from scientists, as it contains the variety of structurally diverse natural products which possess a wide array of biological properties. The present study was conducted to determine ontogenetic and morphogenetic variation of hypericin, chlorogenic acid and flavonoids, as rutin, hyperoside, apigenin-7-O-glucoside, quercitrin and quercetin content in Hypericum origanifolium growing in Turkey. Wild growing plants were harvested at vegetative, floral budding, full flowering, fresh fruiting and mature fruiting stages and dissected into stem, leaf and reproductive tissues and assayed for bioactive compounds by HPLC method. Hypericin, quercetin and quercitrin content in whole plant increased during course of ontogenesis and the highest level was reached in blooming stage. On the contrary, hyperoside content of whole plant decreased linearly with advancing of development stages and the highest level was observed at vegetative stage. Plants produced similar amount of chlorogenic acid at all stages of plant phenology except for mature fruiting at which the amount of this compound was decreased sharply. Among different tissues, reproductive parts accumulated the highest level of hypericin, quercetin and quercitrin, however, leaves produced substantially higher amount of chlorogenic acid and hyperoside. Rutin and apigenin-7-O-glucoside were detectable in all tissues only during fruit maturation. The presence and variation of these bioactive substances in H. origanifolium were reported for the first time.