Volume 5 Special Issue 1 2011
Hypericum

How to reference: Crockett SL, Robson NKB (2011) Taxonomy and Chemotaxonomy of the Genus Hypericum. In: Odabas MS, Çırak C (Eds) Hypericum. Medicinal and Aromatic Plant Science and Biotechnology 5 (Special Issue 1), 1-13

Guest Editors

Mehmet Serhat Odabas, Cüneyt Çırak

The University of Ondokuz Mayis, Samsun, Turkey

www.omu.edu.tr/a/anasayfa/

CONTENTS AND ABSTRACTS

Sara L. Crockett (Austria), Norman K. B. Robson (Great Britain) Taxonomy and Chemotaxonomy of the Genus Hypericum (pp 1-13)

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Invited Review: The genus Hypericum L. (St. John’s Wort, Hypericaceae) includes, at the most recent count, 484 species that are either naturally occurring on, or which have been introduced to, every continent in the world, except Antarctica. These species occur as herbs, shrubs, and infrequently trees, and are found in a variety of habitats in temperate regions and in high mountains in the tropics, avoiding only zones of extreme aridity, temperature and/or salinity. Monographic work on the genus has resulted in the recognition and description of 36 taxonomic sections, delineated by specific combinations of morphological characteristics and biogeographic distribution ranges. Hypericum perforatum L. (common St. John’s wort, section Hypericum), one of the best-known members of the genus, is an important medicinal herb of which extracts are taken for their reported activity against mild to moderate depression. Many other species have been incorporated in traditional medicine systems in countries around the world, or are sold as ornamentals. Several classes of interesting bioactive secondary metabolites, including naphthodianthrones (e.g. hypericin and pseudohypericin), flavonol glycosides (e.g. isoquercitrin and hyperoside), biflavonoids (e.g. amentoflavone), phloroglucinol derivatives (e.g. hyperforin and adhyperforin) and xanthones have been identified from members of the genus. A general overview of the taxonomy of the genus and the distribution of relevant secondary metabolites is presented.

Nicolai M. Nürk (Germany), Sara L. Crockett (Austria) Morphological and Phytochemical Diversity among Hypericum Species of the Mediterranean Basin (pp 14-28)

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Invited Review: The genus Hypericum L. (St. John’s wort, Hypericaceae) includes more than 480 species that occur in temperature or tropical mountain regions of the world. Monographic work on the genus has resulted in the recognition and description of 36 taxonomic sections, delineated by specific combinations of morphological characteristics and biogeographic distribution. The Mediterranean Basin has been recognized as a hot spot of diversity for the genus Hypericum, and as such is a region in which many endemic species occur. Species belonging to sections distributed in this area of the world display considerable morphological and phytochemical diversity. Results of a cladistic analysis, based on 89 morphological characters that were considered phylogenetically informative, are given here. In addition, a brief overview of morphological characteristics and the distribution of pharmaceutically relevant secondary metabolites for species native to this region of the world are presented.

Alessandra Bertoli (Italy), Cüneyt Çırak (Turkey), Jaime A. Teixeira da Silva (Japan) Hypericum Species as Sources of Valuable Essential Oils (pp 29-47)

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Invited Review: Since ancient times, the essential oils (EOs) of many aromatic plants have been used as bioactive ingredients in drug, food and cosmetic formulations all over the world. Significant biological properties have also been attributed to Hypericum EOs. Hypericum is a genus of about 450 species in the Guttiferae family, formerly often treated separately in their own Hypericaceae family. Despite the large number of species, only Hypericum perforatum has been studied in depth by the pharmaceutical industry to control the content of its well known bioactive constituents hypericins, hyperforins and flavonoids in the flowering aerial parts. As a consequence, efficient commercial products based on the hydroalcoholic extracts or oil of H. perforatum are already commercially available as antidepressive agents or to treat skin burns. However, only a few studies have been performed on the EO constituents of H. perforatum and other members of this species. In the last few years some papers have been published on Hypericum EOs, but the number of these studies is still limited and the results are not homogenous enough to justify the use of Hypericum EOs as phytomedicines or dietary supplements. The present study is an overview of the production of EOs from Hypericum species. A summary of the typical EO constituents found in wild or cultivated plants, as well as their biological activities, is provided to point out the most significant Hypericum species, valuable as potential sources of EOs and bioactive ingredients.

Pavol Mártonfi, Lenka Mártonfiová (Slovak Republic) Reproduction Mode in Hypericum and its Consequences (pp 48-52)

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Invited Mini-Review: Several modes of reproduction were described in the genus Hypericum. Besides obligate sexuality, irregularities in meiosis, polyembryony and pseudogamous apomixis were noticed in various taxa of the genus. This review summarizes previous knowledge and also analyses evolutionary consequences of different breeding systems and possible employment of particular reproductive modes for breeding in the genus Hypericum.

Jana Koperdáková, Hedviga Komarovská, Ján Košuth, Eva Čellárová (Slovak Republic) Transgenosis in the Genus Hypericum: Transgenic St. John’s Wort Plants (pp 53-61)

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Invited Review: Modification of the plant genome through genetic transformation represents a powerful tool for studying the gene function via its inactivation or overexpression in planta with an aim to improveproduction capabilities of the plants. Ability of many representatives of the genus Hypericum to produce several important biologically active secondary metabolites makes these plants an important target for such research. Amongst the Hypericum species, the first successfully transformed one through both the most frequently used techniques, Agrobacterium-mediated transformation and particle bombardment was H. perforatum L. Agrobacterium-mediated transformation was recently successfully applied also for H. tetrapterum Fries. and H. tomentosum L. Despite several groups reported successful regeneration of transformed H. perforatum plants, the low transformation efficacy hinder more extensive application of transgenosis in this species. This review summarizes current state of Hypericum transgenic research, especially performed on H. perforatum, including approaches to transform different organs and verify transgenic nature of hairy roots and hairy-root regenerated plants as well as their morphological, physiological, and biochemical properties under in vitro and ex vitro conditions. Flowering and seed production of transgenic plants and future prospects of transformation research of the genus are also discussed.

Eva Čellárová (Slovak Republic) Effect of Exogenous Morphogenetic Signals on Differentiation in Vitro and Secondary Metabolite Formation in the Genus Hypericum (pp 62-69)

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Invited Review: The use of in vitro culture of Hypericum spp. as an experimental system with prospective biotechnological application was triggered by discovering of new activities of hypericin and its derivatives. At the end of the 1990s it was evident that along with anti-depressive effects of Hypericum extracts, there are other very important activities such as anticancer and antiviral which rate the extract and/or some of the individual constituents to the leading herbal products in the world. From among the representatives of this extensive genus, complex research, including in vitro culture and biotechnology, was performed only with H. perforatum. Besides the knowledge we have from this model Hypericum species, there are some partial but promising results from other species of the genus which can be considered as candidates for further investigations and possible future application. This review summarises recent knowledge on some fundamental aspects on hormonal or hormone-like regulation of plantlet differentiation of Hypericum species in vitro, morphogenetic programmes leading to organogenesis, ways of enhancing biosynthesis of profiling secondary metabolites by plant growth substances and/or elicitors and ways of small-scale production of plantlets biomass. To-date results favour differentiated tissues for further studies of biosynthesis of secondary metabolites due to presence of morphological structures serving for their accumulation although promising studies were performed with dedifferentiated cell and callus cultures as well.

Ludger Beerhues (Germany) Biosynthesis of the Active Hypericum perforatum Constituents (pp 70-77)

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Invited Review: Extracts from Hypericum perforatum (St. John’s wort; Clusiaceae) are widely used for the treatment of mild to moderate depression. Four classes of constituents – hyperforins, hypericins, flavonoids, and xanthones – appear to contribute to the antidepressant activity. Interestingly, all four classes of secondary metabolites involve polyketide derivatives. Key reactions of their biosyntheses are catalysed by type III polyketide synthases. These enzymes differ in the starter substrates used, the number of extender units added, and the mode of intramolecular cyclization catalysed. Their products are metabolised by downstream enzymes, such as prenyltransferases and cytochrome P450 enzymes, to give the final active compounds. Despite the medicinal importance of H. perforatum, little is known about the metabolism generating the complex pattern of constituents.

Silvio Caccia, Marco Gobbi (Italy) Hyperforin in St. John’s Wort’s Central Effects: What is the Mechanism of Action? (pp 78-85)

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Invited Review: The constituent(s) accounting for the antidepressant/anxiolytic, nootropic and anti-Alzheimer’s properties of St John’s wort (SJW) extracts is uncertain but the phloroglucinol hyperforin has been described as the main cause. Although its activities in humans have not yet been thoroughly investigated, it has antidepressant-like and anxiolytic-like effects in animal models, while in vitro studies suggest an interaction with the neurotransmitter systems thought to be involved in depression. Some of its actions on the neurotransmitter systems have also been proposed to explain the nootropic effects of SJW extracts, for which another possible explanation followed the in vitro observation that hyperforin activates transient receptor potential canonical 6 channels, which are vital for the formation of dendritic spines, plasticity and memory. In vitro hyperforin also has direct effects on amyloid-β (Aβ) fibrils, providing a potential mechanism for the antagonism of Aβ-induced neurotoxic effects and cognitive impairments. However, considering the low hyperforin brain uptake and concentrations reached in animals after pharmacologically effective doses of SJW extracts or authentic compound and its derivatives, its in vivo actions are unlikely to be due to direct interaction with acknowledgedneurotransmitter transporters and receptors. Although it might interact with some central targets not yet evaluated in vitro, or even primarily act peripherally, thereby influencing central transmission, the central action may be due to one or more metabolites. Further neurochemical studies should therefore be extended to potential metabolite(s) which may have characteristic pharmacodynamic properties. Additional information is also needed on the brain uptake of hyperforin compared to its active metabolite(s). These data should enable us to identify the active principle (parent compound or its metabolite) and its target in the site of action, and undoubtedly help in extrapolating pharmacological findings across species.

Umit Bingol, Belgin Cosge, Bilal Gurbuz (Turkey) Hypericum Species in Flora of Turkey (pp 86-90)

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Invited Mini-Review: Plants of the genus Hypericum (Hypericaceae), comprising over 400 species, have been used for a long time as traditional medicinal plants in various parts of the world. This genus is represented in the Flora of Turkey by 82 species or 98 taxa of which 45 taxa are endemic; the endemism ratio is 45.92%. In Turkey, H. perforatum and H. scabrum are the most domestically traded and exported species.

Gökçen Güzey, Sevda Ibadova, Yusuf Öztürk, Nilgün Öztürk (Turkey), Filippo Maggi, Gianni Sagratini, Massimo Ricciutelli, Sauro Vittori (Italy) Antiproliferative and Antioxidant Effects of Three Hypericum Species of Turkish Origin: H. perforatum, H. montbretii and H. origanifolium (pp 91-99)

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Original Research Paper: Hypericum species have been used in traditional medicine for various purposes including neoplastic diseases. In the present study, antiproliferative and antioxidant activities of extracts of Hypericum perforatum, H. montbretii and H. origanifolium were investigated. Antiproliferative effects of Hypericum extracts were examined by using MTT method on A549 and HeLa cell lines. The β-Carotene-linolenic acid system and the Rancimat method were used to evaluate antioxidant activities, while the DPPH method was employed for testing free radical scavenging activities of the extracts. Total phenolic compounds, flavonoids and flavonols were also measured, whereas major constituents like hypericin, hyperforin, quercetin, quercitrin, isoquercitrin, hyperoside, rutin and chlorogenic acid were determined by HPLC-DAD analyses. The findings indicated that flower extracts of H. montbretii and H. origanifolium have higher antioxidant and antiradical activities than the extract from aerial part of H. perforatum. While flower extract of H. origanifolium has no effect on MTT measurement of A549 cells, leaf extract of this plant at 250 µg/ml concentration exhibits only a weak effect on these cells. Leaf and flower extracts of the same plant possess a similar activity with H. perforatum extract on MTT measurement of HeLa cells. As measured with MTT assay, flower extracts of H. montbretii at the concentrations of 100 and 250 µg/ml exhibit an antiproliferative effects on A549 cells, which is in similar magnitude with H. perforatum extract. Leaf extract of H. montbretii seems to be ineffective on the proliferation of A549 cells, whereas it exhibit only a week antiproliferative effect on HeLa cells at 250 µg/ml concentration. Results suggested that Hypericum species tested have antiproliferative and apoptotic effects, which seems to be related to their antioxidant activities.

Karim Hosni, Kamel Msaada, Thouraya Chahed, Mouna Ben Taarit, Brahim Marzouk (Tunisia) Comparative Analysis of the Essential Oils of Hypericum triquetrifolium Turra. Extracted by Ultrasound, Hydrodistillation and Soxhlet/Dynamic Headspace (pp 100-104)

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Original Research Paper: The essential oil (EO) of Hypericum triquetrifolium Turra., obtained from the aerial parts by ultrasound extraction (USE), hydrodistillation (HD) and Soxhlet/dynamic headspace (SDH) were analyzed by GC-FID and GC-MS. The USE method gave a higher yield than HD and SDH. A total of 60 components were identified with n-octane, α-pinene, β-caryophyllene, 2-methyloctane, n-nonane, germacrene-D, α-selinene and β-cubebene being the main constituents. USE, when compared to HD and SDH, showed high efficiency concomitant to saving time, low energy cost and cleanliness.

Cüneyt Çırak, Ali Kemal Ayan, Mehmet Serhat Odabas (Turkey) Seed Germination of Hypericum triquetrifoliuum and Hypericum heterophyllum (pp 105-107)

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Short Communication: In the present study, seed germination requirements of two Turkish Hypericum species, namely H. triquetrifolium and H. heterophyllum were studied by performing some pre-soaking treatments with the aim of describing suitable germination protocols. Before placing the seeds in Petri dishes, they were soaked in 50, 100 or 150 mg/L gibberellic acid (GA₃); 1, 2 or 3% H₂SO₄; tap water, 40, 50 or 60°C hot water for 30 min. The study was performed under a photoperiod of 18-h light/6-h darkness in growth chambers. In H. triquetrifolium,hot water 40°C (81%) and tap water (80%) treatments produced the highest germination rates followed by GA₃ 100 mg/L (68%), GA₃ 50 mg/L (6%) and GA 150 mg/L (62%) treatments. Unlike the other applications, soaking the seeds in H₂SO₄solutions lowered seed germination when compared to the control. In H. heterophyllum, 2% H₂SO₄ was a unique treatment resulting in enhanced seed germination (20%). The variable germination responses are discussed as a possible result of dormancy involving the presence of a partially hard seed coat and chemical inhibitor(s) in H. triquetrifolium and a hard seed coat in H. heterophyllum.