The labdane diterpene sclareol (labd-14-ene-8, 13-diol) induces apoptosis in human tumor cell lines and suppression of tumor growth in vivo via a p53-independent mechanism of action

Plant-Based Products Originating from Serbia That Affect P-glycoprotein Activity

Our review paper evaluates the impact of plant-based products, primarily derived from plants from Serbia, on P-glycoprotein (P-gp) activity and their potential in modulating drug resistance in cancer therapy. We focus on the role and regulation of P-gp in cellular physiology and its significance in addressing multidrug resistance in cancer therapy. Additionally, we discuss the modulation of P-gp activity by 55 natural product drugs, including derivatives for some of them, based on our team's research findings since 2011. Specifically, we prospect into sesquiterpenoids from the genera Artemisia, Curcuma, Ferula, Inula, Petasites, and Celastrus; diterpenoids from the genera Salvia and Euphorbia; chalcones from the genera Piper, Glycyrrhiza, Cullen, Artemisia, and Humulus; riccardins from the genera Lunularia, Monoclea, Dumortiera, Plagiochila, and Primula; and diarylheptanoids from the genera Alnus and Curcuma. Through comprehensive analysis, we aim to highlight the potential of natural products mainly identified in plants from Serbia in influencing P-gp activity and overcoming drug resistance in cancer therapy, while also providing insights into future perspectives in this field.

Hemisynthesis and cytotoxic evaluation of manoyl oxide analogs from sclareol: effect of two tertiary hydroxyls & Heck coupling on cytotoxicity

Sclareol, a bioactive diterpene alcohol isolated from Salvia sclarea, was subjected to structural modification and cytotoxic evaluation. Boron-Heck-coupled analogs of manoyl oxide were prepared from sclareol in a two-step reaction scheme. In the first step manoyl oxide was prepared from sclareol using cerium (IV) ammonium nitrate. Further the structural modification of manoyl oxide via Palladium (II) catalysed Boron-Heck coupling reaction produced a new series of compounds. All the synthesised compounds were screened for in vitro cytotoxic evaluation against four cancer cell lines HCT-116, MCF-7, MDA-MB231and MDA-MB468. The results showed that manoyl oxide is less active than sclareol. Sclareol shows an IC50 of 2.0 µM compared to manoyl oxide with an IC50 of 50 µM against the MCF-7 cell line. From the results it was inferred that the presence of two tertiary hydroxyls in sclareol are necessary for its cytotoxic activity and Heck coupled analogs are more active than sclareol and manoyl oxide.

Sclareol induces cell cycle arrest and ROS-mediated apoptosis and ferroptosis in lung adenocarcinoma cells

Sclareol (SC) has shown significant anticancer activity against breast and colon cancers among others. However, its ability to precipitate similar anticancer effects in lung cancer has yet to be investigated. To address this issue, SC-treated lung adenocarcinoma cells (A549) were assessed for viability and functional competence as well as the expression of genes related to apoptosis and cell cycling. Our results demonstrated that SC treatment inhibited A549 cell clonogenic features and reduced their migration and invasion potential in a dose-dependent manner. Mechanistically, SC treatment downregulated the expression of cyclin D1 and survivin and upregulated that of p21 and p16, which was associated with a significant increase in the percentage of SubG0 cells. SC treatment is also associated with the induction of both the extrinsic and intrinsic apoptotic pathways, as evidenced by the increased expression and splitting of PARP1 and procaspases 3 and 9 and the reduced expression of antiapoptotic proteins Bcl-2 and Bcl-xL. Increased cell death in SC-treated cells is likely to have resulted from the induction of ferroptosis as suggested by the reduced expression of FPN and the inhibition of the anti-ferroptosis regulator GPX4. In conclusion, the data presented here suggest that SC can reduce lung carcinoma cell growth and metastasis and promote cell death.

Novel hybrids of sclareol and 1,2,4-triazolo[1,5-a]pyrimidine show collateral sensitivity in multidrug-resistant glioblastoma cells

The synthesis of 24 hybrid molecules, consisting of naturally occurring sclareol (SCL) and synthetic 1,2,4-triazolo[1,5-a]pyrimidines (TPs), is described. New compounds were designed with the aim of improving the cytotoxic properties, activity, and selectivity of the parent compounds. Six analogs (12a-f) contained 4-benzylpiperazine linkage, while 4-benzyldiamine linkage was present in eighteen derivatives (12g-r and 13a-f). Hybrids 13a-f consist of two TP units. After purification, all hybrids (12a-r and 13a-f), as well as their precursors (9a-e and 11a-c), were tested on human glioblastoma U87 cells. More than half of the tested synthesized molecules, 16 out of 31, caused a significant reduction of U87 cell viability (more than 75% reduction) at 30 µM. The concentration-dependent cytotoxicity of these 16 compounds was also examined on U87 cells, corresponding multidrug-resistant (MDR) U87-TxR cells with increased P-glycoprotein (P-gp) expression and activity, and normal lung fibroblasts MRC-5. Importantly, 12l and 12r were active in the nanomolar range, while seven compounds (11b, 11c, 12i, 12l, 12n, 12q, and 12r) were more selective towards glioblastoma cells than SCL. All compounds except 12r evaded MDR, showing even better cytotoxicity in U87-TxR cells. In particular, 11c, 12a, 12g, 12j, 12k, 12m, 12n, and SCL showed collateral sensitivity. Hybrid compounds 12l, 12q, and 12r decreased P-gp activity to the same extent as a well-known P-gp inhibitor - tariquidar (TQ). Hybrid compound 12l and its precursor 11c affected different cellular processes including the cell cycle, cell death, and mitochondrial membrane potential, and changed the levels of reactive oxygen and nitrogen species (ROS/RNS) in glioblastoma cells. Collateral sensitivity towards MDR glioblastoma cells was caused by the modulation of oxidative stress accompanied by inhibition of mitochondria.

Advances on Natural Abietane, Labdane and Clerodane Diterpenes as Anti-Cancer Agents: Sources and Mechanisms of Action

Extensive research over the past decades has identified numerous phytochemicals that could represent an important source of anti-cancer compounds. There is an immediate need for less toxic and more effective preventive and therapeutic strategies for the treatment of cancer. Natural compounds are considered suitable candidates for the development of new anti-cancer drugs due to their pleiotropic actions on target events with multiple manners. This comprehensive review highlighted the most relevant findings achieved in the screening of phytochemicals for anticancer drug development, particularly focused on a promising class of phytochemicals such as diterpenes with abietane, clerodane, and labdane skeleton. The chemical structure of these compounds, their main natural sources, and mechanisms of action were critically discussed.

SCLAREIN (SCLAREol contained in zeIN) nanoparticles: Development and characterization of an innovative natural nanoformulation

Sclareol is a labdane diterpene which carries on a broad range of biological activities. However, its poor water solubility and bioavailability are the foremost drawbacks that limit its application in therapeutics. The purpose of this investigation was to develop a natural nanoformulation made up of a biopolymer i.e. zein and sclareol in order to address this issue and to enhance the pharmacological efficacy of the drug. The sclarein nanoparticles (sclareol-loaded zein nanosystems) showed a typical monomodal pattern, characterized by a mean diameter of ~120 nm, a narrow size distribution and a surface charge of ~-30 mV. The evaluation of the entrapment efficiency and the drug-loading capacity of the nanosystems demonstrated the noteworthy ability of the protein matrix to hold sclareol while allowing a gradual release of the compound over time. The nanosystems increased the cytotoxicity of sclareol at a drug concentration of ≥5 μM with respect to the free compound after just 24 h incubation against various cancer cell lines. Indeed, the interaction of tritiated sclarein formulations with cells showed a time-dependent cell uptake of the nanosystems commencing as early as 1 h from the onset of incubation, favouring a significant decrease of the efficacious concentration of the drug.

Anti-proliferative effects of diterpenoids from Sagittaria trifolia L. tubers on colon cancer cells by targeting the NF-κB pathway

A new labdane-type diterpenoid, ent-19-ol-13-epi-manoyl oxide,19-undecane ester, together with ten known diterpenes, were isolated from the ethanolic crude extract of the fresh tubers of Sagittaria trifolia L. The chemical structures of these compounds were determined by extensive 2-D NMR experiments and by comparison with the data reported in the literature. These compounds showed different inhibitory effects on various human cancer cells. Among these, compound 11 exhibited potential inhibition effects against human colon cancer cells. Moreover, flow cytometry demonstrated that compound 11 arrested the cell cycle at the G1 phase and induced cellular apoptosis, accompanied by mitochondrial membrane potential reduction. Mechanistic studies revealed that treatment with compound 11 inhibited IKKα/β phosphorylation and IκBα phosphorylation, which subsequently caused the blockage of NF-κB p65 phosphorylation and nuclear translocation. Compound 11 also inhibited the expression of c-Myc, Cyclin D1, and Bcl-2, the downstream targets of NF-κB. Therefore, our findings provided insight into the anticancer components of Sagittaria trifolia L. tubers, which could facilitate their utilization as functional food ingredients.

Study of the Relationship between Sigma Receptor Expression Levels and Some Common Sigma Ligand Activity in Cancer Using Human Cancer Cell Lines of the NCI-60 Cell Line Panel

Sigma (σ) receptors have attracted great interest since they are implicated in various cellular functions and biological processes and diseases, including various types of cancer. The receptor family consists of two subtypes: sigma-1 (σ1) and sigma-2 (σ2). Both σ receptor subtypes have been proposed as therapeutic targets for various types of cancers, and many studies have provided evidence that their selective ligands (agonists and antagonists) exhibit antiproliferative and cytotoxic activity. Still, the precise mechanism of action of both σ receptors and their ligands remains unclear and needs to be elucidated. In this study, we aimed to simultaneously determine the expression levels of both σ receptor subtypes in several human cancer cell lines. Additionally, we investigated the in vitro antiproliferative activity of some widely used σ1 and σ2 ligands against those cell lines to study the relationship between σ receptor expression levels and σ ligand activity. Finally, we ran the NCI60 COMPARE algorithm to further elucidate the cytotoxic mechanism of action of the selected σ ligands studied herein.

15-Hydroxy-8(17),13(E)-labdadiene-19-carboxylic acid (HLCA) inhibits proliferation and induces cell cycle arrest and apoptosis in ovarian cancer cells

AIM

15-Hydroxy-8(17),13(E)-labdadiene-19-carboxylic acid (HLCA) isolated from Juniperus foetidissima, has been recently identified as an antiproliferative agent; however, the molecular basis of antiproliferative effects of HLCA remains unknown. To investigate it, the current study has emphasized the hypothesis that HLCA induced cell death is a consequence of intracellular reactive oxygen species (ROS) production followed by cell cycle arrest and apoptosis.

MAIN METHODS

Human ovarian OVCAR-3 and Caov-4 cells were treated with various concentrations of HLCA (48 h) and the measurement of intracellular ROS was considered. Then, the potential of HLCA in promoting apoptosis was investigated via flow cytometry, western blot, and caspase activity assay. Also, the inhibitory effect of HLCA on the cell cycle was evaluated using flow cytometry and western blot analysis.

KEY FINDINGS

We found intracellular (ROS) accumulation in HLCA-treated cells. Subsequent observation of the increment in pro-apoptotic Bax as well as the decrement in antiapoptotic Bcl2 revealed that the HLCA-induced cytotoxicity may be triggered by the intrinsic pathway of apoptosis. Our subsequent experiments suggested that caspase-9 and -3 were activated and led the cells to apoptosis during the process. Cell cycle disruption at the G1 phase via down-regulation of cyclin D1 and Cyclin-dependent kinase 4 (CDK4) was another proved mechanism by which HLCA exerts its antiproliferative effects on the ovarian cell lines, OVCAR-3 and Caov-4, especially at relatively lower concentrations.

SIGNIFICANCE

This is the first study that reveals the apoptotic effects of HLCA, suggesting its therapeutic potential as an effective anti-tumor agent. However, further in vivo studies are required to confirm these effects.

Sclareol ameliorated ERCC1-mediated cisplatin resistance in A549 human lung adenocarcinoma cells and a murine xenograft tumor model by suppressing AKT-GSK3β-AP1/Snail and JNK-AP1 pathways

Cisplatin-based chemotherapy is a common first-line regimen for treating non-small cell lung cancer (NSCLC). However, drug resistance is still a major problem. The purposes of this study were to evaluate whether sclareol can reverse cisplatin resistance and to investigate its possible mechanisms. A549 cells, the human NSCLC cells with inherent cisplatin resistance, were used to investigate synergistic effect of sclareol with cisplatin in cell proliferation and migration as well as its regulatory mechanisms in expression of excision repair cross-complementation group 1 (ERCC1), a cisplatin resistance-associated molecule. Nude mice bearing subcutaneous A549 tumors were applied to investigate synergistic activity of sclareol in anti-tumor. As comparing to the cisplatin alone group, the treatment of cisplatin combined with sclareol significantly suppressed survival rate and cell migration of A549 cells. Besides, sclareol also exhibited suppression in ERCC1 expression by inhibiting AKT-GSK3β-AP1/Snail and JNK-AP1 pathways. Furthermore, the experimental data from in vivo study also demonstrated that the combination group of cisplatin and sclareol showed the greatest anti-tumor activity, whose effect could be partially attributed to sclareol-mediated decrease in intratumoral level of ERCC1 protein. Accordingly, sclareol has potential as an adjuvant for the treatment in NSCLC patients with cisplatin resistance.

Coronarin D Induces Apoptotic Cell Death and Cell Cycle Arrest in Human Glioblastoma Cell Line

Glioblastoma (GBM) is the most frequent and highest-grade brain tumor in adults. The prognosis is still poor despite the use of combined therapy involving maximal surgical resection, radiotherapy, and chemotherapy. The development of more efficient drugs without noticeable side effects is urgent. Coronarin D is a diterpene obtained from the rhizome extract of Hedychium coronarium, classified as a labdane with several biological activities, principally anticancer potential. The aim of the present study was to determine the anti-cancer properties of Coronarin D in the glioblastoma cell line and further elucidate the underlying molecular mechanisms. Coronarin D potently suppressed cell viability in glioblastoma U-251 cell line, and also induced G1 arrest by reducing p21 protein and histone H2AX phosphorylation, leading to DNA damage and apoptosis. Further studies showed that Coronarin D increased the production of reactive oxygen species, lead to mitochondrial membrane potential depolarization, and subsequently activated caspases and ERK phosphorylation, major mechanisms involved in apoptosis. To our knowledge, this is the first analysis referring to this compound on the glioma cell line. These findings highlight the antiproliferative activity of Coronarin D against glioblastoma cell line U-251 and provide a basis for further investigation on its antineoplastic activity on brain cancer.

α-Hispanolol Induces Apoptosis and Suppresses Migration and Invasion of Glioblastoma Cells Likely via Downregulation of MMP-2/9 Expression and p38MAPK Attenuation

α-Hispanolol (α-H) is a labdane diterpenoid that has been shown to induce apoptosis in several human cancer cells. However, the effect of α-H in human glioblastoma cells has not been described. In the present work, we have investigated the effects of α-H on apoptosis, migration, and invasion of human glioblastoma cells with the aim of identifying the molecular targets underlying its mechanism of action. The results revealed that α-H showed significant cytotoxicity against human glioma cancer cell lines U87 and U373 in a concentration- and time-dependent manner. This effect was higher in U87 cells and linked to apoptosis, as revealed the increased percentage of sub-G₁ population by cell cycle analysis and acquisition of typical features of apoptotic cell morphology. Apoptosis was also confirmed by significant presence of annexin V-positive cells and caspase activation. Pretreatment with caspase inhibitors diminishes the activities of caspase 8, 9, and 3 and maintains the percentage of viable glioblastoma cells, indicating that α-H induced cell apoptosis through both the extrinsic and the intrinsic pathways. Moreover, we also found that α-H downregulated the anti-apoptotic Bcl-2 and Bcl-xL proteins and activated the pro-apoptotic Bid and Bax proteins. On the other hand, α-H exhibited inhibitory effects on the migration and invasion of U87 cells in a concentration-dependent manner. Furthermore, additional experiments showed that α-H treatment reduced the enzymatic activities and protein levels of matrix metalloproteinase MMP-2 and MMP-9 and increased the expression of TIMP-1 inhibitor, probably via p38MAPK regulation. Finally, xenograft assays confirmed the anti-glioma efficacy of α-H. Taken together, these findings suggest that α-H may exert anti-tumoral effects in vitro and in vivo through the inhibition of cell proliferation and invasion as well as by the induction of apoptosis in human glioblastoma cells. This research describes α-H as a new drug that may improve the therapeutic efficacy against glioblastoma tumors.

Sclareol is a potent enhancer of doxorubicin: Evaluation of the free combination and co-loaded nanostructured lipid carriers against breast cancer

AIMS

In this work, it was sought to determine if there was synergism between doxorubicin (DOX), a well-known antineoplastic, and sclareol (SC), a diterpene from natural origin, in breast cancer treatment. Moreover, it was investigated if their co-loading in the same nanocarrier would result in a gain of activity and/or a toxicity diminishment.

MAIN METHODS

The synergism of the DOX:SC combination was evaluated in MDA-MB-231 and 4T1 cells. A nanostructured lipid carrier (NLC) co-encapsulating DOX and SC in their synergistic molar ratio was prepared and characterised, in terms of mean diameter, zeta potential, DOX encapsulation efficiency, small angle X-ray scattering, differential scanning calorimetry, and polarised light microscopy for further intravenous administration. The anticancer activity of the combination, free and encapsulated, was evaluated in 4T1-tumour bearing mice.

KEY FINDINGS

It was determined that DOX:SC combination at the molar ratio 1:1.9 presents better synergistic anticancer activity than the molar ratio 1:7.5 in vitro. DOX:SC-loaded NLC (NLC-DOX-SC) improved in vitro cytotoxic and in vivo antitumour activity compared to free DOX. Although NLC-DOX-SC and free DOX:SC, at the synergistic molar ratio, showed similar activity in the in vivo study, the free combination provoked body weight loss, behaviour alterations and haematological toxicity in the animals, while this was not observed for NLC-DOX-SC.

SIGNIFICANCE

This work shows that SC and DOX present synergistic anticancer activity for breast cancer treatment whereas NLC-DOX-SC was a feasible alternative to attain the benefits posed by DOX:SC combination but with none to fewer side effects.

Semisynthetic Esters of 17-Hydroxycativic Acid with in Vitro Cytotoxic Activity against Leukemia Cell Lines

A collection of sixteen semisynthetic 17-hydroxycativic acid esters with alcohols containing a tertiary amine group was evaluated for their in vitro cytotoxicity against two human cancer cell lines, THP-1 and U937, and for their effects on the cell cycle and cell death. While 17-hydroxycativic acid itself is not cytotoxic, all the esters displayed cytotoxic activity, with 50% growth inhibition (GI₅₀) values ranging between 3.2 and 23.1 µM. In general, the most potent compounds in both cell lines were esters with four carbon long alcohol residues. There was no clear relationship between the identity of the terminal secondary amine and the activity of the compound. Experiments using the 6-(pyrrolidin-1-yl)pentyl ester, 2c, revealed that this compound activates caspases-3/7 and causes poly(ADP-ribose)polymerase 1 (PARP-1) fragmentation in THP-1 and U937 cells, indicating the induction of apoptotic cell death. These results suggest that further investigation into the anticancer activity of diterpene derivatives and other labdane diterpenes may be fruitful.

The Diterpene Sclareol Vascular Effect in Normotensive and Hypertensive Rats

BACKGROUND:

The diterpene Sclareol has antimicrobial action, cytotoxic and cytostatic effects and anti-tumor activities. However, researches on the cardiovascular system are scarce.

OBJECTIVE:

This study was designed to investigate the mechanisms involved in the Sclareol cardiovascular effect in normotensive and hypertensive rats.

METHODS:

The arterial hypertension was promoted using 2-kidneys 1-clip model in rats. The effect of sclareol on blood pressure was performed by using three dose (10, 20 and 40 mg/kg). Cumulative dose-response curves for Sclareol were determined for endothelium-intact and endothelium-denuded aortic rings in presence or absence of L-NAME and ODQ. The NOx levels were measure in the plasma sample.

RESULTS:

The Sclareol administration in vivo caused a significant reduction in blood pressure in both groups. In vitro the sclareol promoted relaxation in aorta, with endothelium, pre-contracted to Phe. The inhibitors of the nitric oxide synthase and soluble guanylate cyclase were as efficient as the removal of endothelium, in inhibiting the Sclareol-induced relaxation. Otherwise, it was no change of NOx. Also, for unknown reasons, the Sclareol is not selective for hypertensive animals.

CONCLUSION:

The diterpene Sclareol showed in vivo hypotensive and in-vitro vasodilator effects; The chemiluminescence plasmatic NO analysis showed no significant difference between groups and The Sclareol exhibit better effect on normotensive than hypertensive animals to reduce blood pressure. It is concluded that the diterpenes metabolites would be a promising source prototype for the development of new agents in the cardiovascular therapy.

FUNDAMENTO:

O diterpeno Esclareol tem ação antimicrobiana, efeitos citotóxicos e citostáticos e atividades antitumorais. No entanto, pesquisas sobre o sistema cardiovascular são escassas.

OBJETIVO:

Este estudo foi desenvolvido para investigar os mecanismos envolvidos no efeito cardiovascular de Esclareol em ratos normotensos e hipertensos.

MÉTODOS:

A hipertensão arterial foi promovida utilizando modelo de 2 clones de 1-clipe em ratos. O efeito do esclareol sobre a pressão arterial foi realizado utilizando três doses (10, 20 e 40 mg/kg). As curvas dose-resposta cumulativas para Esclareol foram determinadas para anéis aórticos endotélio-intactos e desprovidos de endotélio na presença ou ausência de L-NAME e ODQ. Os níveis de NOx foram medidos na amostra de plasma.

RESULTADOS:

A administração de Esclareol in vivo causou uma redução significativa na pressão sanguínea em ambos os grupos. In vitro o esclareol promoveu relaxamento na aorta, com endotélio, pré-contraído a Phe. Os inibidores da óxido nítrico sintase e da guanilato ciclase solúvel foram tão eficientes quanto a remoção do endotélio, na inibição do relaxamento induzido por Esclareol. Por outra parte, não houve mudança de NOx. Além disso, por razões desconhecidas, o Sclareol não é seletivo para animais hipertensos.

CONCLUSÃO:

O diterpeno Esclareol apresentou efeitos hipotensores in vivo e vasodilatadores in vitro; A análise de NO plasmático por quimioluminescência não mostrou diferença significativa entre os grupos e O Esclareol exibe melhor efeito sobre os animais normotensos do que hipertensos para reduzir a pressão arterial. Conclui-se que os metabólitos de diterpenos seriam um protótipo de fonte promissora para o desenvolvimento de novos agentes na terapia cardiovascular.

Sclareol isolated from Salvia officinalis improves facial wrinkles via an antiphotoaging mechanism

BACKGROUND

Ultraviolet (UV) irradiation triggers skin photoaging processes, which disrupt the normal three-dimensional integrity of skin. UV-induced oxidative stress, both directly and indirectly, stimulates complex signaling pathways. UV radiation activates skin cell surface receptors on a molecular level and triggers severe changes in extracellular matrix (ECM) proteins, resulting in skin photoaging.

AIMS

Sclareol isolated from Salvia officinalis is widely used as a fragrance material. Sclareol is known to exert various biological activities, but its antiphotoaging effect has not been elucidated to date. Therefore, we evaluated wrinkle improvement efficacy of sclareol.

METHODS

Human dermal fibroblast cell line (Hs68) and a reconstructed human epidermis (RHE) model were used to evaluate the antiphotoaging effect of sclareol in vitro. A clinical study treated with 0.02% sclareol-containing cream was conducted to identify the ability of sclareol to improve wrinkles.

RESULTS

First, sclareol enhanced cellular proliferation and blocked UVB-induced cell death. Sclareol inhibited the UVB-induced mRNA expression of matrix metalloproteinases (MMPs) by regulating the protein expression of AP-1 constituents. In RHE model, sclareol recovered the UVB-induced decrease in epidermal thickness and the expression of proliferating cell nuclear antigen (PCNA). In clinical trial, visually assessed changes and several wrinkle parameters were considered to be statistically different between the test and control groups at 12 weeks.

CONCLUSIONS

In this study, sclareol inhibited various photoaging phenomena in human fibroblasts and RHE model. In addition, sclareol-containing cream improved wrinkles in a clinical trial. Taken together, sclareol alleviates facial wrinkle formation via an antiphotoaging mechanism and may be an effective candidate ingredient.

Therapeutic Potential of Essential Oils Focusing on Diterpenes

Among all plant derivates, essential oils (EOs) have gained the attention of many scientists. Diterpenes, a family of components present in some EO, are becoming a milestone in the EOs world. The goal of this review is to describe a scenario of diterpenes taking into health-consumption deportment. Previous studies revealed that diterpenes have antioxidant, antimicrobial, antiviral, antiprotozoal, cytotoxic, anticancer, antigenotoxic, antimutagenic, chemopreventive, antiinflammatory, antinociceptive, immunostimulatory, organoprotective, antidiabetic, lipid-lowering, antiallergic, antiplatelet, antithrombotic, and antitoxin activities. In conclusion, diterpenes may be an immense featuring concern in pharmaceutical consumption from a drug discovery point of view. Copyright © 2016 John Wiley & Sons, Ltd.

Genus Cistus: a model for exploring labdane-type diterpenes' biosynthesis and a natural source of high value products with biological, aromatic, and pharmacological properties

The family Cistaceae (Angiosperm, Malvales) consists of 8 genera and 180 species, with 5 genera native to the Mediterranean area (Cistus, Fumara, Halimium, Helianthemum, and Tuberaria). Traditionally, a number of Cistus species have been used in Mediterranean folk medicine as herbal tea infusions for healing digestive problems and colds, as extracts for the treatment of diseases, and as fragrances. The resin, ladano, secreted by the glandular trichomes of certain Cistus species contains a number of phytochemicals with antioxidant, antibacterial, antifungal, and anticancer properties. Furthermore, total leaf aqueous extracts possess anti-influenza virus activity. All these properties have been attributed to phytochemicals such as terpenoids, including diterpenes, labdane-type diterpenes and clerodanes, phenylpropanoids, including flavonoids and ellagitannins, several groups of alkaloids and other types of secondary metabolites. In the past 20 years, research on Cistus involved chemical, biological and phylogenetic analyses but recent investigations have involved genomic and molecular approaches. Our lab is exploring the biosynthetic machinery that generates terpenoids and phenylpropanoids, with a goal to harness their numerous properties that have applications in the pharmaceutical, chemical and aromatic industries. This review focuses on the systematics, botanical characteristics, geographic distribution, chemical analyses, biological function and biosynthesis of major compounds, as well as genomic analyses and biotechnological approaches of the main Cistus species found in the Mediterranean basin, namely C. albidus, C. creticus, C. crispus, C. parviflorus, C. monspeliensis, C. populifolius, C. salviifolius, C. ladanifer, C. laurifolius, and C. clusii.

Dimeric labdane diterpenes: synthesis and antiproliferative effects

Several diterpenes with the labdane skeleton show biological activity, including antiproliferative effects. Most of the research work on bioactive labdanes has been carried out on naturally occurring diterpenes and semisynthetic derivatives, but much less is known on the effects of diterpene dimers. The aim of the present work was to synthesize dimeric diterpenes from the labdane imbricatolic acid using esters, ethers and the triazole ring as linkers. Some 18 new derivatives were prepared and the compounds were evaluated for antiproliferative activity on human normal fibroblasts (MRC-5) and the following human tumor cell lines: AGS, SK-MES-1, J82 and HL-60. The diethers 8-10, differing in the number of CH₂ units in the linker, presented better antiproliferative activity with a maximum effect for the derivative 9. The best antiproliferative effect against HL-60 cells was found for compounds 3 and 17, with IC₅₀ values of 22.3 and 23.2 μM, lower than that found for the reference compound etoposide (2.23 μM). The compounds 9, 17 and 11 were the most active derivatives towards AGS cells with IC₅₀ values of 17.8, 23.4 and 26.1 μM. A free carboxylic acid function seems relevant for the effect as several of the compounds showed less antiproliferative effect after methylation.