Biologically Active Diterpenoids in the Clerodendrum Genus-A Review.

One of the key areas of interest in pharmacognosy is that of the diterpenoids; many studies have been performed to identify new sources, their optimal isolation and biological properties. An important source of abietane-, pimarane-, clerodane-type diterpenoids and their derivatives are the members of the genus Clerodendrum, of the Lamiaceae. Due to their diverse chemical nature, and the type of plant material, a range of extraction techniques are needed with various temperatures, solvent types and extraction times, as well as the use of an ultrasound bath. The diterpenoids isolated from Clerodendrum demonstrate a range of cytotoxic, anti-proliferative, antibacterial, anti-parasitic and anti-inflammatory activities. This review describes the various biological activities of the diterpenoids isolated so far from species of Clerodendrum with the indication of the most active ones, as well as those from other plant sources, taking into account their structure in terms of their activity, and summarises the methods for their extraction.

The Expression Profiles of the Salvia miltiorrhiza 3-Hydroxy-3-methylglutaryl-coenzyme A Reductase 4 Gene and Its Influence on the Biosynthesis of Tanshinones

Salvia miltiorrhiza is a medicinal plant that synthesises biologically-active tanshinones with numerous therapeutic properties. An important rate-limiting enzyme in the biosynthesis of their precursors is 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR). This study presents the organ-specific expression profile of the S. miltiorrhiza HMGR4 gene and its sensitivity to potential regulators, viz. gibberellic acid (GA3), indole-3-acetic acid (IAA) and salicylic acid (SA). In addition, it demonstrates the importance of the HMGR4 gene, the hormone used, the plant organ, and the culture environment for the biosynthesis of tanshinones. HMGR4 overexpression was found to significantly boost the accumulation of dihydrotanshinone I (DHTI), cryptotanshinone (CT), tanshinone I (TI) and tanshinone IIA (TIIA) in roots by 0.44 to 5.39 mg/g dry weight (DW), as well as TIIA in stems and leaves. S. miltiorrhiza roots cultivated in soil demonstrated higher concentrations of the examined metabolites than those grown in vitro. GA3 caused a considerable increase in the quantity of CT (by 794.2 µg/g DW) and TIIA (by 88.1 µg/g DW) in roots. In turn, IAA significantly inhibited the biosynthesis of the studied tanshinones in root material.

Transformed Shoots of Dracocephalum forrestii W.W. Smith from Different Bioreactor Systems as a Rich Source of Natural Phenolic Compounds.

Transformed shoots of the Tibetan medicinal plant Dracocephalum forrestii were cultured in temporary immersion bioreactors (RITA and Plantform) and in nutrient sprinkle bioreactor (NSB) for 3 weeks in MS (Murashige and Skoog) liquid medium with 0.5 mg/L BPA (N-benzyl-9-(2-tetrahydropyranyl)-adenine) and 0.2 mg/L IAA (indole-3-acetic acid). The greatest biomass growth index (GI = 52.06 fresh weight (FW) and 55.67 dry weight (DW)) was observed for shoots in the RITA bioreactor, while the highest multiplication rate was found in the NSB (838 shoots per bioreactor). The levels of three phenolic acids and five flavonoid derivatives in the shoot hydromethanolic extract were evaluated using UHPLC (ultra-high performance liquid chromatography). The predominant metabolite was rosmarinic acid (RA)-the highest RA level (18.35 mg/g DW) and total evaluated phenol content (24.15 mg/g DW) were observed in shoots grown in NSB. The NSB culture, i.e., the most productive one, was evaluated for its antioxidant activity on the basis of reduction of ferric ions (ferric reducing antioxidant power, FRAP) and two scavenging radical (O2•- and DPPH, 1,1-diphenyl-2-picrylhydrazyl radical) assays; its antibacterial, antifungal, and antiproliative potential against L929 cells was also tested (3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test). The plant material revealed moderate antioxidant and antimicrobial activities and demonstrated high safety in the MTT test-no cytotoxicity at concentrations up to 50 mg/mL was found, and less than a 20% decrease in L929 cell viability was observed at this concentration.

The effect of purine-type cytokinin on the proliferation and production of phenolic compounds in transformed shoots of Dracocephalum forrestii.

Dracocephalum forrestii is a perennial, endemic to China plant with a number of pharmaceutical properties. Transformed shoots of the species spontaneously regenerated from hairy roots induced by Agrobacterium rhizogenes. The transgenic nature of the shoots was confirmed by polymerase chain reaction (PCR). The shoot culture was multiplied on Murashige and Skoog (MS) medium with 0.2 mg/l IAA and 0.2, 0.5, 1.0, 2.0 or 5.0 mg/l purine-type cytokinins (mT, BAR, BPA or BAP). The highest multiplication rate (about thirteen shoot or buds per explant) was obtained on MS medium with 0.2 mg/l mT after four weeks of culture. The phenolic compounds present in the hydromethanolic extracts from the D. forrestii transgenic shoots were characterized using UPLC-PDA-ESI-MS. The shoots were found to biosynthesize three phenolic acids and five flavonoid glycosides. UHPLC analysis of the hydromethanolic extracts found the predominant phenolic acid to be rosmarinic acid, with its highest content observed in shoots cultivated with 5.0 mg/l BPA. In contrast, the greatest production of flavonoid derivatives (especially acacetin derivatives) was observed in the medium supplemented with 2 mg/l BPA.

The Increase of Triterpene Saponin Production Induced by Trans-Anethole in Hairy Root Cultures of Panax quinquefolium.

In vitro cultivation is an effective way to increase pharmaceutical production. To increase ginsenoside production in hairy root cultures of American ginseng, the present study uses trans-anethole as an elicitor. The content of nine triterpene saponins was determined: Rb1, Rb2, Rb3, Rc, Rd, Rg1, Rg2, Re and Rf. Trans-anethole was found to stimulate saponin synthesis regardless of exposure time (24 and 72 h). Twenty-four hour exposure to 1 µmol trans-anethole in the culture medium resulted in the highest increase of total saponin content (twice that of untreated roots), and optimum accumulation of Rb-group saponins, with ginsenoside Rc dominating (8.45 mg g-1 d.w.). In contrast, the highest mean content of protopanaxatriol derivatives was obtained for 10 µmol trans-anethole. The Re metabolite predominated, reaching a concentration of 5.72 mg g-1 d.w.: a 3.9-fold increase over untreated roots. Elicitation with use of trans-anethole can therefore be an effective method of increasing ginsenoside production in shake flasks.

Yeast Extract Stimulates Ginsenoside Production in Hairy Root Cultures of American Ginseng Cultivated in Shake Flasks and Nutrient Sprinkle Bioreactors.

One of the most effective strategies to enhance metabolite biosynthesis and accumulation in biotechnological systems is the use of elicitation processes. This study assesses the influence of different concentrations of yeast extract (YE) on ginsenoside biosynthesis in Panax quinquefolium (American ginseng) hairy roots cultivated in shake flasks and in a nutrient sprinkle bioreactor after 3 and 7 days of elicitation. The saponin content was determined using HPLC. The maximum yield (20 mg g-1 d.w.) of the sum of six examined ginsenosides (Rb1, Rb2, Rc, Rd, Re and Rg1) in hairy roots cultivated in shake flasks was achieved after application of YE at 50 mg L-1 concentration and 3 day exposure time. The ginsenoside level was 1.57 times higher than that attained in control medium. The same conditions of elicitation (3 day time of exposure and 50 mg L-1 of YE) also favourably influenced the biosynthesis of studied saponins in bioreactor cultures. The total ginsenoside content was 32.25 mg g-1 d.w. and was higher than that achieved in control medium and in shake flasks cultures. Obtained results indicated that yeast extract can be used to increase ginsenoside production in hairy root cultures of P. quinquefolium.

Taxodione and Extracts from Salvia austriaca Roots as Human Cholinesterase Inhibitors.

Taxodione, an abietane diterpenoid, was isolated from Salvia austriaca transformed roots grown in in vitro conditions. The compound is known to have antibacterial, cytotoxic and anti-tumour properties. This study evaluates the ability of pure taxodione and extracts obtained from the S. austriaca hairy roots and roots from field-grown plants to inhibit human acetylcholinesterase and butyrylcholinesterase. Both extracts were found to have similar actions against acetylcholinesterase. The IC50 for extracts from transformed and untransformed roots were 142.5 and 139.5 µg ml(-1), respectively. The highest activity towards human acetylcholinesterase was demonstrated by taxodione (IC50 = 54.84 µg ml(-1)). With respect to BChE inhibition, the root extracts demonstrated stronger activity (IC50 = 23.6 µg ml(-1): field-grown plants and 41.6 µg ml(-1): transformed roots) than taxodione (IC50 = 195.9 µg ml(-1)). Taxodione showed significant cytotoxicity against A549 cell line (IC50 = 9.1 µg ml(-1)), whereas the activities for the extracts from S. austriaca roots of field-grown plants (IC50 = 75.7 µg ml(-1)) and hairy roots (IC50 = 86.2 µg ml(-1)) were lower. Computer modelling suggests that taxodione should not demonstrate cardiotoxic or genotoxic activity. It also indicates that taxodione should demonstrate very rapid transport from the body with very good blood-brain barrier penetration, but with no cumulative effect on the human body. The obtained results indicate that taxodione is a safe compound and may be used for further investigations in pharmacological activities.

EVALUATION OF ANTIOXIDANT PROPERTIES OF METHANOLIC EXTRACTS FROM LEAVES AND ROOTS OF REHMANNIA GLUTINOSA LIBOSCH. IN HUMAN BLOOD.

Compounds with antioxidant activity may protect different elements of blood from damaging effects of oxidative stress. The present in vitro study was designed to examine the antioxidant activity of methanolic extracts from leaves and roots of R. glutinosa plants against damages induced by oxidative stress. Oxidative stress was stimulated in human plasma and human blood platelet samples by the strong biological oxidant--hydrogen peroxide (H2O2) or H2O2/Fe (the donor of hydroxyl radicals). In experimental trials, the level of biomarker of lipid peroxidation--TBARS was significantly decreased by the action of methanolic extracts from R. glutinosa leaves. Therefore, it seems that the methanolic extract from leaves of the plants may be a new source of bioactive antioxidant natural compounds. It may be also an active pharmacological agent or a food supplement for healthy subjects and for people with different diseases (cardiovascular diseases and cancer) induced by oxidative stress.

Abietane diterpenoids from Salvia sclarea transformed roots as growth inhibitors of pathogenic Acanthamoeba spp.

Amoebae from the genus Acanthamoeba are known agents leading to various diseases such as granulomatous amoebic encephalitis (GAE), a chronic progressive disease of the central nervous system, amoebic keratitis (AK), chronic eye infection, amoebic pneumitis (AP), chronic lung infection, and skin infections. It is known that various synthetic anti-Acanthamoeba substances are ineffective. Therefore, other substances, e.g., natural plant compounds, are the focus of biological investigations regarding anti-parasite activity. In this work, the ability of four abietane diterpenoids (ferruginol, salvipisone, aethiopinone, and 1-oxo-aethiopinone) to inhibit Acanthamoeba growth is reported. All investigated compounds were active against Acanthamoeba growing in vitro. Among them, ferruginol demonstrated the highest activity against Acanthamoeba. This compound inhibited Acanthamoeba growth by about 72% in a 3-day exposure period (IC50 17.45 µM), while aethiopinone and 1-oxo-aethiopinone demonstrated this activity at the level of 55-56%. Salvipisone reduced the growth of Acanthamoeba in vitro culture by 39%. For this compound, the value of IC50 was 701.94 µM after 72 h of exposure.

An unusual taxodione derivative from hairy roots of Salvia austriaca.

From a root culture of Salvia austriaca, transformed with Agrobacterium rhizogenes, a new diterpenoid was isolated and its chemical structure was determined as 7-(2-oxohexyl)-11-hydroxy-6, 12-dioxo-7,9(11),13- abietatriene [= 7-(2-oxohexyl)-taxodione] on the basis of spectroscopic methods, especially 1D and 2D NMR, and by comparison with structurally related compounds. This compound represents a hitherto unknown 2-oxohexyl diterpenoid derivative. Cytotoxic studies revealed that the new compound exhibited high cytotoxic activity against three cancer cell lines with IC(50) values ranging from 0.63 to 0.72µM. Its cytotoxic effectiveness against the cancer cells was ten fold higher than that of taxodione.

Chemical composition and biological activities of essential oil from Salvia sclarea plants regenerated in vitro.

The essential oils obtained by hydrodistillation of dried aerial parts of Salvia sclarea L. plants, regenerated in vitro and reproduced from seeds, were analyzed by GC and GC-MS. The oils from in vitro and in vivo plants were compared in respect to their chemical composition as well as antimicrobial and cytotoxic activities. The chemical profiles of both oils were very similar, although the yield of essential oil from in vitro plants was lower (0.1%, v/w) than the oil yield isolated from in vivo S. sclarea plants (0.2%, v/w). Both oils showed antimicrobial and cytotoxic activity. The oil from in vitro regenerated plants of S. sclarea exhibited stronger cytotoxic action against NALM-6 cell lines in comparison with the essential oil from in vivo plants.

Salvipisone and aethiopinone from Salvia sclarea hairy roots modulate staphylococcal antibiotic resistance and express anti-biofilm activity.

Two diterpenoids, salvipisone (Salv) and aethiopinone (Aeth), isolated from hairy roots of Salvia sclarea, were tested with respect to their activity against methicillin-resistant Staphylococcus aureus (MRSA) and S. epidermidis (MRSE) strains, cultured as planktonic cells or as adherent biofilms. The standard CLSI method, MTT reduction assay or confocal laser scanning microscopy (CLSM) were used for this purpose and also applied for testing the susceptibility to oxacillin, vancomycin, linezolid and their potential synergy with diterpenoids (evaluated as a fractional inhibitory concentration (FIC) index). Salv and Aeth were shown to be bactericidal or bacteriostatic against S. aureus and S. epidermidis planktonic cultures. Both diterpenoids, at the concentrations of 1/2 MIC, showed synergy with antibiotics representing the beta-lactam, glycopeptide and oxazolidinone groups. None of the antibiotics used at a high concentration killed the staphylococcal biofilms. On the contrary, Salv and Aeth decreased the number of live biofilm cells by 45.7 - 77.1% and slightly reduced the biofilm inhibitory concentration of oxacillin. Diterpenoids also changed the parameters of biofilm morphology, as shown by the CLSM image processing package (PHLIP). It was concluded that salvipisone and aethiopinone (relatively highly lipophilic, log P respectively = 3.4; 4.8) synergized the action of beta-lactam antibiotics towards MRSA and MRSE probably by alteration of cell surface hydrophobicity and cell wall/membrane permeability, but not by changing penicillin-binding protein, PBP2a expression and penicillinase production or by direct binding to the cell wall peptidoglycan and teichoic acids.