Neo-clerodane diterpenes from Salvia herbacea

The drug likeness analysis of anti-inflammatory clerodane diterpenoids

Inflammation is an active defense response of the body against external stimuli. Long term low-grade inflammation has been considered as a deteriorated factor for aging, cancer, neurodegeneration and metabolic disorders. The clinically used glucocorticoids and non-steroidal anti-inflammatory drugs are not suitable for chronic inflammation. Therefore, it's urgent to discover and develop new effective and safe drugs to attenuate inflammation. Clerodane diterpenoids, a class of bicyclic diterpenoids, are widely distributed in plants of the Labiatae, Euphorbiaceae and Verbenaceae families, as well as fungi, bacteria, and marine sponges. Dozens of anti-inflammatory clerodane diterpenoids have been identified on different assays, both in vitro and in vivo. In the current review, the up-to-date research progresses of anti-inflammatory clerodane diterpenoids were summarized, and their druglikeness was analyzed, which provided the possibility for further development of anti-inflammatory drugs.

Hydroxy-neo-Clerodanes and 5,10-seco-neo-Clerodanes from Salvia decora

Preliminary analysis of the mass spectrometric (MS) and NMR spectroscopic data of the primary fractions from the biologically active extract of Salvia decora revealed spectra that are characteristic for neo-clerodane-type diterpenoids. MS-guided isolation of the bioactive fractions led to the isolation of three new chemical entities, including two hydroxy-neo-clerodanes (1 and 2) and one acylated 5,10-seco-neo-clerodane (3), along with three known diterpenoids (4-6), ursolic acid (7), and eupatorin (8). The structures of the new compounds were established by analysis of the 1D and 2D NMR and MS data, whereas their absolute configuration was deduced using a combination of experimental and theoretical ECD data and confirmed by X-ray crystallography (1 and 4). Furthermore, compounds 1, 3, 4, and 6-8 were evaluated as hPTP1B_1-400 (human protein tyrosine phosphatase) inhibitors, where 7 showed the best activity, with an IC₅₀ value in the lower μM range. Additionally, compound 7 was evaluated as an α-glucosidase inhibitor. The affinity constant of the 7-hPTP1B_1-400 complex was determined by quenching fluorescence experiments (k_a = 1.3 × 10⁴ M^-1), while the stoichiometry ratio (1:1 protein-ligand) was determined by a continuous variation method.

Further galphimines from a new population of Galphimia glauca

Both DNA barcoding and phylogenetic data of the studied botanical material suggested the existence a new population of Galphimia glauca. Their leaves afforded three new nor-3,4-seco-friedelanes named galphimines M-O, together with known galphimines D, E, G, and I. Galphimines M and N possess bicyclic orthoacetates which are the first examples of orthoesters found in the Malpighiaceae family, while galphimine O has a 27,20-δ-lactone moiety. The structures elucidation followed from spectroscopic means and the absolute configuration followed from single crystal X-ray diffraction analyses. Tests for antibacterial and antifungal activities of galphimines N and M showed no promising effects.

Bioactive terpenoids from Croton laui

Two new highly-oxygenated neo-clerodane diterpenoids, 3S-acetoxyl-mollotucin D dilactone ester (1) and 6S-crotoeurin C (2), and a new lupane-type triterpene, 16β-hydroxyl-3β-O-trans-coumaroyl-betulin (6), as well as three known analogues (3-5) were obtained from the leaves of Croton laui. The structures of the new compounds were determined by extensive spectroscopic methods, and their absolute configurations were determined by combination of single-crystal X-ray diffraction analysis, electronic circular dichroism (ECD) spectra, and literature data. Compounds 2 and 3 exhibited inhibitory activities of lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 macrophages with IC₅₀ values of 1.2 and 1.6 μM, respectively. Additionally, compound 6 exhibited activity against Col205 and HepG2 cell lines with IC₅₀ values of 12.9 and 17.7 μM, respectively.

Recent advances in allelopathy for weed control: from knowledge to applications

Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry.

Pharmacological evaluation of 2-angeloyl ent-dihydrotucumanoic acid

CONTEXT

Gymnosperma glutinosum (Spreng.) Less. (Asteraceae) is a bush used for the empirical treatment of pain, fever, and cancer. An ent-neo-clerodane diterpene (2-angeloyl ent-dihydrotumanoic acid; ADTA) was isolated from G. glutinosum.

OBJECTIVE

This study evaluates the cytotoxic, anti-inflammatory, and antinociceptive effects of ADTA.

MATERIALS AND METHODS

The cytotoxic effects of ADTA (1-350 μM) were evaluated using the MTT assay with human tumorigenic (SW-620, MDA-MB231, SKLU1, SiHa, and PC-3), and non-tumorigenic (HaCaT) cells for 48 h. The in vitro anti-inflammatory effects of ADTA (0.23-460 μM) were assessed using murine peritoneal macrophages stimulated with LPS and estimating the levels of pro-inflammatory mediators for 48 h. The antinociceptive effects of ADTA (25-100 mg/kg p.o.) were evaluated using two in vivo models of chemical-induced nociception during 1 h.

RESULTS

ADTA lacked cytotoxic activity (IC₅₀> 100 μM) on tumorigenic cells. In non-tumorigenic cells (HaCaT), ADTA exerted low cytotoxic effects (IC₅₀=273 μM). ADTA, at concentrations of 115 μM or higher, decreased the release of pro-inflammatory mediators. The maximum antinociceptive effects of ADTA in the acetic acid-induced abdominal constrictions by ADTA was found at 100 mg/kg (63%), whereas in the formalin test at phase 1 and phase 2, ADTA (100 mg/kg) decreased the licking time by 47 and 71%, respectively.

CONCLUSION

The results indicate that ADTA, obtained from G. glutinosum, exerts moderate in vitro anti-inflammatory and in vivo antinociceptive effects, but lacks cytotoxic effects on human cancer cells.

neo-Clerodane Diterpenoids from Salvia polystachya Stimulate the Expression of Extracellular Matrix Components in Human Dermal Fibroblasts

Eleven neo-clerodane diterpenoids (1-11) including the new analogues 1, 2, and 10, and 3',5,6,7-tetrahydroxy-4'-methoxyflavone (12) were isolated from the aerial parts of Salvia polystachya. Polystachyne G (1) and 15-epi-polystachyne G (2) were isolated as an epimeric mixture, containing a 5-hydroxyfuran-2(5H)-one unit in the side chain at C-12 of the neo-clerodane framework. Polystachyne H (10) contains a 1(10),2-diene moiety and a tertiary C-4 hydroxy group. The structures of these compounds were established by analysis of their NMR spectroscopic and MS spectrometric data. The absolute configurations of compounds 3, 4, and 10 were determined through single-crystal X-ray diffraction analysis. The antibacterial, antifungal, and phytotoxic activities of the diterpenoids were determined. In addition, the stimulatory effect of the expression of extracellular matrix components of nine of the isolates (1-8 and 11) was assayed. Compounds 1-4, 8, and 11 increased the expression of the genes codifying for type I, type III, and type V collagens and for elastin.

Bioactive Terpenoids from Salvia plebeia: Structures, NO Inhibitory Activities, and Interactions with iNOS

A phytochemical investigation to obtain new NO inhibitors resulted in the identification of six new (1-6) and four known (7-10) terpenoids from Salvia plebeia. Compounds 1 and 2 are new diterpenoids, 3-5 are new meroditerpenoids, 6-9 are sesquiterpenoids, and 10 is a known meroditerpenoid. The structures of these isolates were determined by routine NMR experiments and X-ray diffraction, as well as the electronic circular dichroism spectra. Compounds 1-4 are diterpenoids carrying an oxygen bridge, and 6 is a rare copane-type sesquiterpenoid with a bridged tricyclic framework. The isolates inhibited NO generation induced by lipopolysaccharide in BV-2 cells. The possible mechanism of NO inhibition of some bioactive compounds was also investigated using molecular docking, which revealed interactions of bioactive compounds with the iNOS protein.

Clerodane diterpenes: sources, structures, and biological activities

Covering: 1990 to 2015The clerodane diterpenoids are a widespread class of secondary metabolites and have been found in several hundreds of plant species from various families and in organisms from other taxonomic groups. These substances have attracted interest in recent years due to their notable biological activities, particularly insect antifeedant properties. In addition, the major active clerodanes of Salvia divinorum can be used as novel opioid receptor probes, allowing greater insight into opioid receptor-mediated phenomena, as well as opening additional areas for chemical investigation. This article provides extensive coverage of naturally occurring clerodane diterpenes discovered from 1990 until 2015, and follows up on the 1992 review by Merritt and Ley in this same journal. The distribution, chemotaxonomic significance, chemical structures, and biological activities of clerodane diterpenes are summarized. In the cases where sufficient information is available, structure activity relationship (SAR) correlations and mode of action of active clerodanes have been presented.

neo-Clerodane Diterpenoids and Other Constituents of Salvia filipes

A series of neo-clerodane-type diterpenoids were isolated from the aerial parts of Salvia filipes, including the new compounds 4-epi-polystachyne A (1), salvifilines A (3), C (7), and D (8), and salvifiline B, which was isolated as the 15-O-methyl derivatives 4/5. In addition, the five known diterpenoids (2, 9-12), together with ursolic, oleanolic, and betulinic acids, and the flavone eupatorin were also isolated. The structures were determined by analysis of their spectroscopic data, mainly 1D and 2D NMR. The structure of salvifiline D was confirmed by X-ray analysis. The cytotoxic activities of the diterpenoids were evaluated, but all were inactive against a panel of six human cancer cell lines.

Structural elucidation and evaluation of multidrug-resistance modulatory capability of amarissinins A-C, diterpenes derived from Salvia amarissima

Three new diterpenes (amarissinins A-C, 1-3) containing several oxygenated functionalities were isolated from the leaves and flowers of Salvia amarissima. The structures of these compounds were established through the analysis of their NMR spectroscopy and mass spectrometry data. The structures of compounds 1 and 2 were confirmed by single crystal X-ray diffraction. Compound 2 was identified as a C-10 epimer of dugesin F (5). The cytotoxic activity of these compounds against five human cancer cell lines was determined. Additionally, the capability to modulate the multidrug resistance (MDR) in the MCF-7 cancer cell line resistant to vinblastine was tested.

Teotihuacanin, a Diterpene with an Unusual Spiro-10/6 System from Salvia amarissima with Potent Modulatory Activity of Multidrug Resistance in Cancer Cells

Teotihuacanin (1), an unusual rearranged clerodane diterpene with a new carbon skeleton containing a spiro-10/6 bicyclic system, was isolated from the leaves and flowers of Salvia amarissima. Its structure was determined through spectroscopic analyses. Its absolute configuration was established by single-crystal X-ray diffraction. Compound 1 showed potent modulatory activity of multidrug resistance in vinblastine-resistant MCF-7 cancer cell line (reversal fold, RFMCF-7/Vin+ > 10703) at 25 μg/mL.

Bioactive clerodane diterpenoids from the twigs of Casearia balansae

Eight new clerodane diterpenes, balanspenes A-H (1-8), along with two known analogues (9 and 10), were isolated from the twigs of Casearia balansae. The structures of 1-8 were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analysis, and the absolute configurations of compounds 1, 4, and 7 were confirmed by comparing their experimental CD spectra with those calculated by the time-dependent density functional theory method. Compounds 4-7, 9, and 10 were found to possess the property of being able to stimulate NGF-mediated neurite outgrowth from PC12 cells.

Studies toward the Development of Antiproliferative Neoclerodanes from Salvinorin A

The success rate for central nervous system (CNS) drug candidates in the clinic is relatively low compared to the industry average across other therapeutic areas. Penetration through the blood-brain barrier (BBB) to reach the therapeutic target is a major obstacle in development. The rapid CNS penetration of salvinorin A has suggested that the neoclerodane nucleus offers an excellent scaffold for developing antiproliferative compounds that enter the CNS. The Liebeskind-Srogl reaction was used as the main carbon-carbon bond-forming step toward the synthesis of quinone-containing salvinorin A analogues. Quinone-containing salvinorin A analogues were shown to have antiproliferative activity against the MCF7 breast cancer cell line, but show no significant activity at the κ-opioid receptors. In an in vitro model of BBB penetration, quinone-containing salvinorin A analogues were shown to passively diffuse across the cell monolayer. The analogues, however, are substrates of P-glycoprotein, and thus further modification of the molecules is needed to reduce the affinity for the efflux transporter.

5,10-seco-neo-clerodanes and neo-clerodanes from Salvia microphylla

Two new 5,10-seco-neo-clerodanes, salvimicrophyllins A and B (1 and 2), and two new neo-clerodanes, salvimicrophyllins C and D (3 and 4), were isolated from the leaves and flowers of Salvia microphylla. The structures of these compounds were elucidated mainly by analysis of their NMR spectroscopic and mass spectrometric data. The relative configurations of the salvimicrophyllins were determined by analysis of NOESY spectra and ECD curves, and the relative configuration of compound 2 was confirmed by single-crystal X-ray diffraction crystallography.

Hydroxyclerodanes from Salvia shannoni

Six new hydroxyclerodanes (1-6), named sepulturins A-F, and four known diterpenes were isolated from the leaves of Salvia shannoni. The structures of these compounds were established by extensive analysis of their NMR and MS spectroscopic data. The relative configurations of compounds 1 and 2 were determined by NOESY experiments and were confirmed by single-crystal X-ray diffraction studies. All of the isolated diterpenes possess tertiary OH groups. The structure of infuscatin (7), a clerodane previously isolated from S. infuscata, was revised. Cytotoxic, antiprotozoal, and anti-inflammatory activities of these compounds were evaluated.