Phytochemistry Reviews (v.14, #1)

Secondary plant metabolites, and in particular monoterpenes, have been recognised as potential medicinal agents for centuries. As such, terpenes have been the focus of a plethora of scientific studies examining various aspects of their bioactivity. In particular, antimicrobial activity and anticancer potential have been studied extensively. Whilst the antimicrobial and anticancer activity of terpenes has been demonstrated in vitro, fewer studies have been conducted examining specific aspects of the mechanisms of antimicrobial action and anticancer efficacy in vivo. The purpose of this review is therefore to examine recent advances in the areas of antimicrobial and anticancer activity.
Keywords: Essential oil; Tea tree oil; Antibacterial; Cytotoxicity; Antitumour

Terpenoids form the largest group of plant specialized metabolites and exhibit essential functions in plant metabolism, propagation and defence. Since several mono- and sesquiterpenoids, like artemisinin, menthol and nootkatone, have proven beneficial for mankind, they also possess high socio-economic value. The general mechanisms of terpene biosynthesis are understood and enzymes catalysing the formation of the isoprenoid basic carbon skeletons have been described frequently. In the subsequent pathway steps, it is mainly cytochromes P450 that catalyse the decoration of these basic skeletons and thereby contribute significantly to the structural diversity observed. Structure–function relationship, even though discussed intensively, is poorly understood for this enzyme family; even with the phylogenic relationship well established identification of the functionality of the single enzymes is challenging, and, so far, only a few have been characterized. This review provides an overview over cytochromes P450 participating in the biosynthesis of mono- and sesquiterpenes. Only enzymes that have been described thoroughly after purification and heterologous expression are included in this review and their characteristic features are discussed.
Keywords: Cytochrome P450; Isoprenoids; Plant specialized metabolism; Terpenoids

Dimeric acylphloroglucinols in Hypericum species from sections Brathys and Trigynobrathys by Gari Vidal Ccana-Ccapatinta; Francisco Maikon Corrêa de Barros; Henrique Bridi; Gilsane Lino von Poser (25-50).
Hypericum is a prolific source of acylphloroglucinol derivatives. Unlike the monomeric polyisoprenylated acylphloroglucinols hyperforin and adhyperforin, which are the main phloroglucinols in Hypericum perforatum (section Hypericum), dimeric structures are to the best of our knowledge exclusively reported in sections Brathys and Trigynobrathys belonging to the genus Hypericum. Their occurrence, as well as the analytical properties of the thirty-one dimeric acylphloroglucinols currently reported for Hypericum spp. are reviewed. Additionally, the presence of dimeric acylphloroglucinol in four Peruvian Hypericum species is presented and their chemotaxonomic significance explored.
Keywords: Chemotaxonomy; Isolation; NMR spectroscopy; Tautomerism; Translucent glands

Major secondary metabolites of Iris spp. by Wirginia Kukula-Koch; Elwira Sieniawska; Jarosław Widelski; Otgonbataar Urjin; Paweł Głowniak; Krystyna Skalicka-Woźniak (51-80).
Roots and rhizomes of many Iris species are well known as precious sources of isoflavones. They have been used in traditional medicine to treat respiratory disorders and decrease smooth muscles activity. Recent advances in their phytochemistry and phytomedicine have revealed potent anticholinesterase, antineoplastic and anti-plasmodial activities of iris constituents. Furthermore, decoctions from rhizomes have been successfully used among patients with hormone-related diseases. Except for isoflavones, the main chemical components of Iris are xanthones, quinones, flavons, terpenes and simple phenolics, with multiple biological activities. This contribution reviews the research progress of the past 30 years relating to the chemistry, recovery of secondary metabolites, their separation by means of TLC and HPLC techniques and spectral data of the most common chemical components of iris extracts. Special attention is paid to ultraviolet spectroscopy, infrared spectroscopy, LC–mass spectroscopy and nuclear magnetic resonance analyses of isoflavones, flavons, xanthones and terpenes.
Keywords: Isolation; Iris spp.; Spectral analysis; Structure elucidation

Allium ursinum: botanical, phytochemical and pharmacological overview by Danuta Sobolewska; Irma Podolak; Justyna Makowska-Wąs (81-97).
Ramson—Allium ursinum L. is a medicinal and dietary plant species with a long tradition of use. This mini-review summarizes the current knowledge on the phytochemistry and pharmacological properties of this valuable plant, with special emphasis on antimicrobial, cytotoxic, antioxidant, and cardio-protective effects.
Keywords: Allium ursinum ; Biological activity; Ramson; Steroidal saponins; Sulfur compounds

The genus Casearia: a phytochemical and pharmacological overview by Li Xia; Qiang Guo; Pengfei Tu; Xingyun Chai (99-135).
Casearia (Salicaceae sensu lato) species have been used as folk medicines in South American and Asian countries since ancient times. Previous phytochemical screenings demonstrated that the Casearia plants mainly contain clerodane diterpenoids, sesquiterpenoids, phenylpropanoids and other constituents from different chemical classes. The pharmacological studies confirmed that the crude extracts or individual compounds from the genus showed cytotoxic, hypoglycemic, antiulcer, and anti-inflammatory activities, as well as anti-snake venom property. In this review we presented a summary of the secondary metabolites isolated from Casearia species based on the published literatures through May 2013. In addition to the traditional medicinal use of Casearia plants and their taxonomic characteristics, we focused on the known biological activities of the plants and discussed them in detail here.
Keywords: Casearia ; Salicaceae sensu lato ; Flacourtiaceae; Clerodane diterpenoid; Cytotoxicity; Hypoglycemic; Anti-snake venom; Chemotaxonomy

Natural autophagy regulators in cancer therapy: a review by Qian Ding; Jiaolin Bao; Wenwen Zhao; Yangyang Hu; Jinjian Lu; Xiuping Chen (137-154).
Autophagy is a complicated self-eating response of cells to external or internal stimuli. This process involves cellular degradation through the lysosomes of dysfunctional or unnecessary cellular components or organelles to maintain basic energy levels. This nonapoptotic programmed cell death, similar to other main phenomena of cell biology such as apoptosis and differentiation, has been implicated in the pathogenesis of a series of disorders, such as neurodegenerative diseases, cardiovascular diseases, and especially in cancer. Increasing evidence has suggested that the autophagy pathways may provide potential targets for cancer intervention, although their precise roles in cancer initiation and progression remain controversial. Natural products are very important sources of chemotherapeutics agents. Regulation of autophagy could be an important mechanism contributing to the beneficial effect of quite a few natural products. Herein, we briefly introduce the characteristics and roles of autophagy in cancer and systematically summarize the natural autophagy regulators, with emphasis on apigenin, berberine, beta-elemene, capsaicin, curcumin, genistein, kaempferol, oridonin, paclitaxel, quercetin, resveratrol, silybin, triptolide, and ursolic acid, with the aim to provide information for novel avenues on cancer therapies based on autophagy.
Keywords: Autophagy; Cancer; Natural products; Drug discovery